|Cluster A (odd)|
|Cluster B (dramatic)|
|Cluster C (anxious)|
Psychopathy (//), also known as—though sometimes differentiated from—sociopathy (//), is traditionally defined as a personality disorder characterized by enduring antisocial behavior, diminished empathy and remorse, and disinhibited or bold behavior. It may also be defined as a continuous aspect of personality, representing scores on different personality dimensions found throughout the population in varying combinations. The definition of psychopathy has varied significantly throughout the history of the concept; different definitions continue to be used that are only partly overlapping and sometimes appear contradictory.
Hervey M. Cleckley, an American psychiatrist, probably influenced the initial diagnostic criteria for antisocial personality reaction/disturbance in the Diagnostic and Statistical Manual of Mental Disorders (DSM), as did American psychologist George E. Partridge. The DSM and International Classification of Diseases (ICD) subsequently introduced the diagnoses of antisocial personality disorder (ASPD) and dissocial personality disorder respectively, stating that these diagnoses have been referred to (or include what is referred to) as psychopathy or sociopathy. Canadian psychologist Robert D. Hare later repopularized the construct of psychopathy in criminology with his Psychopathy Checklist.
Although no psychiatric or psychological organization has sanctioned a diagnosis titled "psychopathy", assessments of psychopathic characteristics are widely used in criminal justice settings in some nations, and may have important consequences for individuals. The study of psychopathy is an active field of research, and the term is also used by the general public, in popular press, and in fictional portrayals.
- 1 Definition
- 2 Signs and symptoms
- 3 Causes
- 4 Mechanisms
- 5 Diagnosis
- 5.1 Tools
- 5.2 Comorbidity
- 5.3 Further considerations
- 6 Management
- 7 Prognosis
- 8 Epidemiology
- 9 Society and culture
- 10 History
- 11 See also
- 12 References
- 13 Bibliography
- 14 External links
Researchers have noted that there appear to be at least two different conceptions of psychopathy, each with differing policy implications. Jennifer L. Skeem et al. distinguished Cleckleyan psychopathy (named after Hervey Cleckley's early conception of psychopathy, entailing bold, disinhibited behavior, low anxiety and "feckless disregard") and criminal psychopathy (a "meaner, more aggressively disinhibited conception of psychopathy that explicitly entails persistent and sometimes serious criminal behavior", typically operationalized with the Psychopathy Checklist), the latter of which is used as the modern clinical concept. Due to the profound implications that a label of "psychopath" can have—including in terms of decisions about punishment severity, treatment, etc.—efforts have been made to clarify the meaning of the term, e.g. by reconciling seemingly disparate conceptions such as those mentioned.
The triarchic model, formulated by Christopher J. Patrick et al., suggests that different conceptions of psychopathy emphasize three observable characteristics to varying degrees. Analyses have been made with respect to the applicability of measurement tools such as the Psychopathy Checklist (PCL, PCL-R) and Psychopathic Personality Inventory (PPI) to this model.
- Boldness. Low fear including stress-tolerance, toleration of unfamiliarity and danger, and high self-confidence and social assertiveness. The PCL-R measures this relatively poorly and mainly through Facet 1 of Factor 1. Similar to PPI Fearless dominance. May correspond to differences in the amygdala and other neurological systems associated with fear.
- Disinhibition. Poor impulse control including problems with planning and foresight, lacking affect and urge control, demand for immediate gratification, and poor behavioral restraints. Similar to PCL-R Factor 2 and PPI Impulsive antisociality. May correspond to impairments in frontal lobe systems that are involved in such control.
- Meanness. Lacking empathy and close attachments with others, disdain of close attachments, use of cruelty to gain empowerment, exploitative tendencies, defiance of authority, and destructive excitement seeking. The PCL-R in general is related to this but in particular some elements in Factor 1. Similar to PPI Coldheartedness but also includes elements of subscales in Impulsive antisociality.
An early and influential analysis from Harris and colleagues indicated a discrete category may underlie PCL-R psychopathy, but this was only found for the behavioral Factor 2 items. Marcus, John, and Edens more recently performed a series of statistical analyses on PPI scores and concluded psychopathy may best be conceptualized as having a "dimensional latent structure" like depression.
Marcus et al. repeated the study on a larger sample of prisoners, using the PCL-R and seeking to rule out other experimental or statistical issues that may have produced the previously different findings. They again found that the psychopathy measurements do not appear to be identifying a discrete type (a taxon). They suggest that while for legal or other practical purposes an arbitrary cut-off point on trait scores might be used, there is actually no clear scientific evidence for an objective point of difference by which to label some people "psychopaths;" in other words, a "psychopath" may be more accurately described as someone who is "relatively psychopathic".
The PCL-R was developed for research, not clinical forensic diagnosis, and even for research purposes to improve understanding of the underlying issues, it is necessary to examine dimensions of personality in general rather than only a constellation of traits.
There are different views as to which personality dimensions are more central in regard to psychopathy. Besides dimensions described elsewhere in this article, studies have linked psychopathy to alternative dimensions such as antagonism (high), conscientiousness (low) and anxiousness (low, or sometimes high). Psychopathy has also been linked to high psychoticism—a theorized dimension referring to tough, aggressive or hostile tendencies. Aspects of this that appear associated with psychopathy are lack of socialization and responsibility, impulsivity, sensation-seeking (in some cases), and aggression.
Otto Kernberg, from a particular psychoanalytic perspective, believed psychopathy should be considered as part of a spectrum of pathological narcissism, that would range from narcissistic personality on the low end, malignant narcissism in the middle, and psychopathy at the high end. However, narcissism is generally seen as only one possible aspect of psychopathy as broadly defined.
Psychopathy, narcissism and Machiavellianism, three personality traits that are together referred to as the dark triad, share certain characteristics, such as a callous-manipulative interpersonal style. The dark tetrad refers to these traits with the addition of sadism.
Signs and symptoms
Psychopathy is a personality disorder which has symptoms expressed over a wide range of settings. Socially, it expresses extensive callous and manipulative self-serving behaviors with no regard for others, and often is associated with repeated delinquency, crime and violence, but may also present itself in other, maybe even successful social settings. Mentally, impairments in processes related to affect (emotion) and cognition, particularly socially related mental processes, have been found in those with the disorder which suggest that their destructive social behavior is borne from these aberrant mental processes. Developmentally, symptoms of psychopathy have been identified in young children with conduct disorder, and is suggestive of at least a partial constitutional factor that influences its development.
In terms of simple correlations, the PCL-R manual states an average score of 22.1 has been found in North American prisoner samples, and that 20.5% scored 30 or higher. An analysis of prisoner samples from outside North America found a somewhat lower average value of 17.5. Studies have found that psychopathy scores correlated with repeated imprisonment, detention in higher security, disciplinary infractions, and substance misuse.
Psychopathy, as measured with the PCL-R in institutional settings, shows in meta-analyses small to moderate effect sizes with institutional misbehavior, postrelease crime, or postrelease violent crime with similar effects for the three outcomes. Individual studies give similar results for adult offenders, forensic psychiatric samples, community samples, and youth. The PCL-R is poorer at predicting sexual re-offending. This small to moderate effect appears to be due largely to the scale items that assess impulsive behaviors and past criminal history, which are well-established but very general risk factors. The aspects of core personality often held to be distinctively psychopathic generally show little or no predictive link to crime by themselves. For example, Factor 1 of the PCL-R and Fearless dominance of the PPI-R have smaller or no relationship to crime, including violent crime. In contrast, Factor 2 and Impulsive antisociality of the PPI-R are associated more strongly with criminality. Factor 2 has a relationship of similar strength to that of the PCL-R as a whole. The antisocial facet of the PCL-R is still predictive of future violence after controlling for past criminal behavior which, together with results regarding the PPI-R which by design does not include past criminal behavior, suggests that impulsive behaviors is an independent risk factor. Thus, the concept of psychopathy may perform poorly when attempted to be used as a general theory of crime.
Studies have suggested a strong correlation between psychopathy scores and violence, and the PCL-R emphasizes features that are somewhat predictive of violent behavior. Researchers, however, have noted that psychopathy is dissociable from and not synonymous with violence.
It has been suggested that psychopathy is associated with "instrumental", also known as predatory, proactive, or "cold blooded" aggression, a form of aggression characterized by reduced emotion and conducted with a goal differing from but facilitated by the commission of harm. One conclusion in this regard was made by a 2002 study of homicide offenders, which reported that the homicides committed by homicidal offenders with psychopathy were almost always (93.3%) primarily instrumental, significantly more than the proportion (48.4%) of those committed by non-psychopathic homicidal offenders, with the instrumentality of the homicide also correlated with the total PCL-R score of the offender as well as their scores on the Factor 1 "interpersonal-affective" dimension. However, contrary to the equating of this to mean exclusively "in cold blood", more than a third of the homicides committed by psychopathic offenders involved some component of emotional reactivity as well. In any case, FBI profilers indicate that serious victim injury is generally an emotional offense, and some research supports this, at least with regard to sexual offending. One study has found more serious offending by non-psychopathic offenders on average than by offenders with psychopathy (e.g. more homicides versus more armed robbery and property offenses) and another that the Affective facet of the PCL-R predicted reduced offense seriousness.
Some clinicians suggest that assessment of the construct of psychopathy does not necessarily add value to violence risk assessment. A large systematic review and meta-regression found that the PCL performed the poorest out of nine tools for predicting violence. In addition, studies conducted by the authors or translators of violence prediction measures, including the PCL, show on average more positive results than those conducted by more independent investigators. There are several other risk assessment instruments which can predict further crime with an accuracy similar to the PCL-R and some of these are considerably easier, quicker, and less expensive to administrate. This may even be done automatically by a computer simply based on data such as age, gender, number of previous convictions and age of first conviction. Some of these assessments may also identify treatment change and goals, identify quick changes that may help short-term management, identify more specific kinds of violence that may be at risk, and may have established specific probabilities of offending for specific scores. Nonetheless, the PCL-R may continue to be popular for risk assessment because of its pioneering role and the large amount of research done using it.
The Federal Bureau of Investigation reports that psychopathic behavior is consistent with traits common to some serial killers, including sensation seeking, a lack of remorse or guilt, impulsivity, the need for control, and predatory behavior. It has also been found that the homicide victims of psychopathic offenders were disproportionately female in comparison to the more equitable gender distribution of victims of non-psychopathic offenders.
Psychopathy has been associated with commission of sexual crime, with some researchers arguing that it is correlated with a preference for violent sexual behavior. A 2011 study of conditional releases for Canadian male federal offenders found that psychopathy was related to more violent and non-violent offences but not more sexual offences. For child molesters, psychopathy was associated with more offences. A study on the relationship between psychopathy scores and types of aggression in a sample of sexual murderers, in which 84.2% of the sample had PCL-R scores above 20 and 47.4% above 30, found that 82.4% of those with scores above 30 had engaged in sadistic violence (defined as enjoyment indicated by self-report or evidence) compared to 52.6% of those with scores below 30, and total PCL-R and Factor 1 scores correlated significantly with sadistic violence. Despite this, it is reported that offenders with psychopathy (both sexual and non-sexual offenders) are about 2.5 times more likely to be granted conditional release compared to non-psychopathic offenders.
In considering the issue of possible reunification of some sex offenders into homes with a non-offending parent and children, it has been advised that any sex offender with a significant criminal history should be assessed on the PCL-R, and if they score 18 or higher than they should be excluded from any consideration of being placed in a home with children under any circumstances. There is, however, increasing concern that PCL scores are too inconsistent between different examiners, including in its use to evaluate sex offenders.
Researchers have discussed the possibility of psychopathy being associated with organised crime, economic crime and war crimes. Terrorists are sometimes considered psychopathic, and comparisons may be drawn with traits such as antisocial violence, a selfish world view that precludes the welfare of others, a lack of remorse or guilt, and blame externalization. However, John Horgan, author of The Psychology of Terrorism, argues that such comparisons could also then be drawn more widely: for example, to soldiers in wars. It has also been noted that coordinated terrorist activity requires organization, loyalty and ideological fanaticism often to the extreme of sacrificing oneself for an ideological cause. Traits such as a self-centered disposition, unreliability, poor behavioral controls, and unusual behaviors may disadvantage or preclude psychopathic individuals in conducting organized terrorism.
Studies on perpetrators of domestic abuse find that domestic abusers have high rates of psychopathy, with the prevalence estimated to be at around 15-30%. Furthermore, the commission of domestic violence is correlated with Factor 1 of the PCL-R, which describes the emotional deficits and the callous and exploitative interpersonal style found in psychopathy. The prevalence of psychopathy among domestic abusers indicate that the core characteristics of psychopathy, such as callousness, remorselessness, and a lack of close interpersonal bonds, predispose those with psychopathy to committing domestic abuse, and suggest that the domestic abuses committed by these individuals are callously perpetrated (i.e. instrumentally aggressive) rather than a case of emotional aggression and therefore may not be amenable to the types of psychosocial interventions commonly given to domestic abuse perpetrators.
It has been speculated that some with the disorder may be socially successful, expressing their antisocial behavior through more covert avenues such as social manipulation or white collar crime. Such individuals are sometimes referred to as "successful psychopaths", and do not necessarily have extensive histories of traditional antisocial behavior as characteristic of traditional psychopathy.
Childhood and adolescent precursors
The PCL:YV is an adaptation of the PCL-R for individuals aged 13–18 years. It is, like the PCL-R, done by a trained rater based on an interview and an examination of criminal and other records. The "Antisocial Process Screening Device" (APSD) is also an adaptation of the PCL-R. It can be administered by parents or teachers for individuals aged 6–13 years. High psychopathy scores for both juveniles, as measured with these instruments, and adults, as measured with the PCL-R and other measurement tools, have similar associations with other variables, including similar ability in predicting violence and criminality. Juvenile psychopathy may also be associated with more negative emotionality such as anger, hostility, anxiety, and depression.
There are moderate to high correlations between psychopathy rankings from late childhood to early adolescence. The correlations are considerably lower from early- or mid-adolescence to adulthood. In one study most of the similarities were on the Impulsive- and Antisocial-Behavior scales. Of those adolescents who scored in the top 5% highest psychopathy scores at age 13, less than one third (29%) were classified as psychopathic at age 24. Some recent studies have also found poorer ability at predicting long-term, adult offending.
Conduct disorder is diagnosed based on a prolonged pattern of antisocial behavior in childhood and/or adolescence, and may be seen as a precursor to ASPD. Some researchers have speculated that there are two subtypes of conduct disorder which mark dual developmental pathways to adult psychopathy. The DSM allows differentiating between childhood onset before age 10 and adolescent onset at age 10 and later. Childhood onset is argued to be more due to a personality disorder caused by neurological deficits interacting with an adverse environment. For many, but not all, childhood onset is associated with what is in Terrie Moffitt's developmental theory of crime referred to as "life-course- persistent" antisocial behavior as well as poorer health and economic status. Adolescent onset is argued to more typically be associated with short-term antisocial behavior.
It has been suggested that the combination of early-onset conduct disorder and ADHD may be associated with life-course-persistent antisocial behaviors as well as psychopathy. There is evidence that this combination is more aggressive and antisocial than those with conduct disorder alone. However, it is not a particularly distinct group since the vast majority of young children with conduct disorder also have ADHD. Some evidence indicates that this group has deficits in behavioral inhibition, similar to that of adults with psychopathy. They may not be more likely than those with conduct disorder alone to have the interpersonal/affective features and the deficits in emotional processing characteristic of adult psychopaths. Proponents of different types/dimensions of psychopathy have seen this type as possibly corresponding to adult secondary psychopathy and increased disinhibition in the triarchic model.
The DSM-5 includes a specifier for those with conduct disorder who also display a callous, unemotional interpersonal style across multiple settings and relationships. The specifier is based on research which suggests that those with conduct disorder who also meet criteria for the specifier tend to have a more severe form of the disorder with an earlier onset as well as a different response to treatment. Proponents of different types/dimensions of psychopathy have seen this as possibly corresponding to adult primary psychopathy and increased boldness and/or meanness in the triarchic model.
Dysfunctions in the prefrontal cortex and amygdala regions of the brain have been associated with specific learning impairments in psychopathy. Since the 1980s, scientists have linked traumatic brain injury, including damage to these regions, with violent and psychopathic behavior. Patients with damage in such areas resembled "psychopathic individuals" whose brains were incapable of acquiring social and moral knowledge; those who acquired damage as children may have trouble conceptualizing social or moral reasoning, while those with adult-acquired damage may be aware of proper social and moral conduct but be unable to behave appropriately. Dysfunctions in the amygdala and ventromedial prefrontal cortex may also impair stimulus-reinforced learning in psychopaths, whether punishment-based or reward-based. People scoring 25 or higher in the PCL-R, with an associated history of violent behavior, appear to have significantly reduced mean microstructural integrity in their uncinate fasciculus—white matter connecting the amygdala and orbitofrontal cortex. There is evidence from DT-MRI, of breakdowns in the white matter connections between these two important areas.
Although some studies have suggested inverse relationships between psychopathy and intelligence, including with regards to verbal IQ, Hare and Neumann state that a large literature demonstrates at most only a weak association between psychopathy and IQ, noting that the early pioneer Cleckley included good intelligence in his checklist due to selection bias (since many of his patients were "well educated and from middle-class or upper-class backgrounds") and that "there is no obvious theoretical reason why the disorder described by Cleckley or other clinicians should be related to intelligence; some psychopaths are bright, others less so". Studies also indicate that different aspects of the definition of psychopathy (e.g. interpersonal, affective (emotion), behavioral and lifestyle components) can show different links to intelligence, and the result can depend on the type of intelligence assessment (e.g. verbal, creative, practical, analytical).
Emotion recognition and empathy
A large body of research suggests that psychopathy is associated with atypical responses to distress cues (e.g. facial and vocal expressions of fear and sadness), including decreased activation of the fusiform and extrastriate cortical regions, which may partly account for impaired recognition of and reduced autonomic responsiveness to expressions of fear, and impairments of empathy. The underlying biological surfaces for processing expressions of happiness are functionally intact in psychopaths, although less responsive than those of controls. The neuroimaging literature is unclear as to whether deficits are specific to particular emotions such as fear. Some recent fMRI studies have reported that emotion perception deficits in psychopathy are pervasive across emotions (positives and negatives). Studies on children with psychopathic tendencies have also shown such associations. Meta-analyses have also found evidence of impairments in both vocal and facial emotional recognition for several emotions (i.e., not only fear and sadness) in both adults and children/adolescents.
A recent study using offenders with psychopathy found that under certain circumstances they could willfully empathize with others. Functional neuroimaging was performed while the subjects were watching videos of a person harming another individual. While reduced empathic brain activation relative to the controls was observed in the control condition, the empathic reaction of the psychopathic offenders initiated the same way it did for controls when they were instructed to empathize with the harmed individual, and the area of the brain relating to pain was activated when the psychopathic offenders were asked to imagine how the harmed individual felt. The research suggests that individuals with psychopathy could switch empathy on at will, which would enable them to be both callous as well as charming. The team who conducted the study say it is still unknown how to transform this willful empathy into the spontaneous empathy most people have, though they propose it could be possible to bring psychopaths closer to rehabilitation by helping them to activate their "empathy switch". Others suggested that despite the results of the study, it remained unclear whether the experience of empathy by these psychopathic individuals was the same as that of controls, and also questioned the possibility of devising therapeutic interventions that would make the empathic reactions more automatic.
Work conducted by Jean Decety with large samples of incarcerated offenders with psychopathy offers additional insights. In one study, the offenders were scanned while viewing video clips depicting people being intentionally hurt. They were also tested on their responses to seeing short videos of facial expressions of pain. The participants in the high-psychopathy group exhibited significantly less activation in the ventromedial prefrontal cortex, amygdala and periaqueductal gray parts of the brain, but more activity in the striatum and the insula when compared to control participants. In a second study, the subjects with psychopathy exhibited a strong response in pain-affective brain regions when taking an imagine-self perspective, but failed to recruit the neural circuits that were activated in controls during an imagine-other perspective—in particular the ventromedial prefrontal cortex and amygdala—which may contribute to their lack of empathic concern.
Despite studies suggesting deficits in emotion perception and imagining others in pain, professor Simon Baron-Cohen claims psychopathy is associated with intact cognitive empathy, which would imply an intact ability to read and respond to behaviors, social cues and what others are feeling. Psychopathy is, however, associated with impairment in the other major component of empathy—affective (emotional) empathy—which includes the ability to feel the suffering and emotions of others (what scientists would term as emotional contagion), and those with the condition are therefore not distressed by the suffering of their victims. Those with autism, on the other hand, often are impaired in both the affective and cognitive facets of empathy.
Psychopathy has been associated with amorality—an absence of, indifference towards, or disregard for moral beliefs. There are few firm data on patterns of moral judgment. Studies of developmental level (sophistication) of moral reasoning found all possible results—lower, higher or the same as non-psychopaths. Studies that compared judgments of personal moral transgressions versus judgments of breaking conventional rules or laws found that psychopaths rated them as equally severe, whereas non-psychopaths rated the rule-breaking as less severe.
A study comparing judgments of whether personal or impersonal harm would be endorsed in order to achieve the rationally maximum (utilitarian) amount of welfare found no significant differences between subjects high and low in psychopathy. However, a further study using the same tests found that prisoners scoring high on the PCL were more likely to endorse impersonal harm or rule violations than non-psychopathic controls were. The psychopathic offenders who scored low in anxiety were also more willing to endorse personal harm on average.
Assessing accidents, where one person harmed another unintentionally, psychopaths judged such actions to be more morally permissible. This result has been considered a reflection of psychopaths' failure to appreciate the emotional aspect of the victim's harmful experience.
Studies have identified potential genetic and non-genetic contributors to psychopathy, including influences on brain function. Proponents of the triarchic model believe that psychopathy results from the interaction of genetic predispositions and an adverse environment. What is adverse may differ depending on the underlying predisposition: for example, it is hypothesized that persons having high boldness may respond poorly to punishment but may respond better to rewards and secure attachments.
Studies of the personality characteristics typical of individuals with psychopathy have found moderate genetic (as well as non-genetic) influences. On the PPI, fearless dominance and impulsive antisociality were similarly influenced by genetics and uncorrelated with each other. Genetic factors may generally influence the development of psychopathy while environmental factors affect the specific expression of the traits that predominate. A study on a large group of children found more than 60% heritability for "callous-unemotional traits" and that conduct problems among children with these traits had a higher heritability than among children without these traits.
Studies have suggested a connection between the impulsive, aggressive and violent behavior associated with antisocial personality disorder and psychopathy and a low-activity variant of the monoamine oxidase A (MAO-A) gene (dubbed the "warrior gene"), encoding for the MAO-A enzyme that regulates neurotransmitter activity by breaking down the neurotransmitters serotonin, norepinephrine, and dopamine. The polymorphism associated with behavioral traits consists of 30 bases repeated between 2 and 5 times upstream of the MAO-A gene, and produces comparatively less MAO-A enzyme. The 2R and 3R variants (linked to low MAO-A activity) were found to vary widely in demographic prevalence among different ethnic groups. 5.5% of black men and 0.1% of Caucasian men carry the 2R allele, whereas 59% of African-American men, 56% of Maori men, 54% of Asian men, and 34% of Caucasian men carry the 3R variant. Low MAO-A activity is associated with a significantly increased risk of aggressive and antisocial behavior.
Associations between a variation of the 5-HTTLPR region of the gene that encodes the serotonin transporter and psychopathic traits have been found, and the gene has been suggested to be a significant factor in psychopathy's aetiology. 5-HTTLPR regulates the expression of the serotonin transporter on neuron synapses, and is one of the most studied genetic polymorphisms, researched for its association with various mental disorders. The high activity "long" (L) allele of 5-HTTLPR, which increases the expression of the serotonin transporter relative to the "short" (S), were found to be associated with PCL-R Factor 1 scores, or the interpersonal-affective traits of psychopathy, which describes its core character disturbances (self-centeredness, cold-heartedness). The L allele is known to be associated with emotional resilience, reduced emotional response to evocative situations, and a reduced risk of mood disorders. A study on youths found that the L homozygous allele correlated with psychopathic traits among those of a low socioeconomic background, indicating a possible environmental influence on the expression of psychopathy. Another study replicated the association of the L homozygous allele and the interpersonal-affective psychopathic traits in men in a correctional setting, but didn't find a connection between a history of abuse in childhood and such traits. It is theorized that reduced emotional and stress response that the L allele promotes may interact in a synergistic manner with other gene variations that promote a reduced emotional response and a low sensitivity to distress to predispose an individual to psychopathy.
A study by Farrington of a sample of London males followed between age 8 and 48 included studying which factors scored 10 or more on the PCL:SV at age 48. The strongest factors included having a convicted parent, being physically neglected, low involvement of the father with the boy, low family income, and coming from a disrupted family. Other significant factors included poor supervision, harsh discipline, large family size, delinquent sibling, young mother, depressed mother, low social class, and poor housing. There has also been association between psychopathy and detrimental treatment by peers. However, it is difficult to determine the extent of an environmental influence on the development of psychopathy because of evidence of its strong heritability.
Researchers have linked head injuries with psychopathy and violence. Since the 1980s, scientists have associated traumatic brain injury, such as damage to the prefrontal cortex, including the orbitofrontal cortex, with psychopathic behavior and a deficient ability to make morally and socially acceptable decisions, a condition that has been termed "acquired sociopathy", or "pseudopsychopathy". Individuals with damage to the area of the prefrontal cortex known as the ventromedial prefrontal cortex show remarkable similarities to psychopathic individuals, displaying reduced autonomic response to emotional stimuli, deficits in aversive conditioning, similar preferences in moral and economic decision making, and diminished empathy and social emotions such as guilt and shame. These emotional and moral impairments may be especially severe when the brain injury occurs at a young age. Children with early damage in the prefrontal cortex may never fully develop social or moral reasoning and become "psychopathic individuals ... characterized by high levels of aggression and antisocial behavior performed without guilt or empathy for their victims". Additionally, damage to the amygdala may impair the ability of the prefrontal cortex to interpret feedback from the limbic system, which could result in uninhibited signals that manifest in violent and aggressive behavior.
Primary and secondary
Psychopathy can emerge from an amalgamation of divergent factors. One conceptualization suggests two dichotomous origins, termed primary and secondary psychopathy. Using this model of research, these different types are believed to have distinct etiologies. Primary psychopathy arises from mostly genetically driven factors, whereas environmental factors may play a stronger role in secondary psychopathy. Some research suggests that individuals with secondary psychopathy have high levels of anxiety and are more receptive to environmental stressors, while individuals with primary psychopathy have low-anxiety and a blunted fear response. There is substantial evidence that anxiety can play a mediating role in many psychopathologies, including psychopathy. However, there is insufficient evidence supporting the different characteristic and etiological processes thought to underlie primary and secondary psychopathy at this time, though some have been theorised.
Psychopathy is associated with several adverse life outcomes as well as increased risk of disability and death due to factors such as violence, accidents, homicides, and suicides. This, in combination with the evidence for genetic influences, is evolutionarily puzzling and may suggest that there are compensating evolutionary advantages, and researchers within evolutionary psychology have proposed several evolutionary explanations. According to one hypothesis, some traits associated with psychopathy may be socially adaptive, and psychopathy may be a frequency-dependent, socially parasitic strategy, which may work as long as there is a large population of altruistic and trusting individuals, relative to the population of psychopathic individuals, to be exploited. It is also suggested that some traits associated with psychopathy such as early, promiscuous, adulterous, and coercive sexuality may increase reproductive success. Robert Hare has stated that many psychopathic males have a pattern of mating with and quickly abandoning women, and thereby have a high fertility rate, resulting in children that may inherit a predisposition to psychopathy.
Criticism includes that it may be better to look at the contributing personality factors rather than treat psychopathy as a unitary concept due to poor testability. Empirical evidence regarding the suggested reproductive success is lacking. Furthermore, if psychopathy is caused by the combined effects of a very large number of adverse mutations then each mutation may have such a small an effect that it escapes natural selection. The personality is thought to be influenced by a very large number of genes and may be disrupted by random mutations, and psychopathy may instead be a product of a high mutation load. Psychopathy has alternatively been suggested to be a spandrel, a byproduct, or side-effect, of the evolution of adaptive traits rather than an adaptation in itself.
Some laboratory research demonstrate correlations between psychopathy and atypical responses to aversive stimuli, including weak conditioning to painful stimuli and poor learning of avoiding responses that cause punishment, as well as low reactivity in the autonomic nervous system as measured with skin conductance while waiting for a painful stimulus but not when the stimulus occurs. While it has been argued that the reward system functions normally, some studies have also found reduced reactivity to pleasurable stimuli. Psychopathic individuals have also had difficulty switching from an ongoing action despite environmental cues signaling a need to do so. This may explain the difficulty responding to punishment, although it is unclear if it can explain findings such as deficient conditioning. There may be methodological issues regarding the research. While establishing a range of idiosyncrasies on average in linguistic and affective processing under certain conditions, this research program has not confirmed a common pathology of psychopathy.
Thanks to advancing MRI studies, experts are able to visualize specific brain differences and abnormalities of individuals with psychopathy in areas that control emotions, social interactions, ethics, morality, regret, impulsivity and conscience within the brain. Blair, a researcher who pioneered research into psychopathic tendencies stated, “With regard to psychopathy, we have clear indications regarding why the pathology gives rise to the emotional and behavioral disturbance and important insights into the neural systems implicated in this pathology”. Dadds et al., remarks that despite a rapidly advancing neuroscience of empathy, little is known about the developmental underpinnings of the psychopathic disconnect between affective and cognitive empathy.
A 2008 review by Weber et al. suggested that psychopathy is sometimes associated with brain abnormalities in prefrontal-temporo-limbic regions that are involved in emotional and learning processes, among others. Neuroimaging studies have found structural and functional differences between those scoring high and low on the PCL-R in a 2011 review by Skeem et al. stating that they are "most notably in the amygdala, hippocampus and parahippocampal gyri, anterior and posterior cingulate cortex, striatum, insula, and frontal and temporal cortex". A 2010 meta-analysis found that antisocial, violent and psychopathic individuals had reduced structure function in the right orbitofrontal cortex,right anterior cingulate cortex and left dorsolateral prefrontal cortex.
The amygdala and frontal areas have been suggested as particularly important. People scoring 25 or higher in the PCL-R, with an associated history of violent behavior, appear on average to have significantly reduced microstructural integrity between the white matter connecting the amygdala and orbitofrontal cortex (such as the uncinate fasciculus). The evidence suggested that the degree of abnormality was significantly related to the degree of psychopathy and may explain the offending behaviors. Furthermore, changes in the amygdala have been associated with "callous-unemotional" traits in children. However, the amygdala has also been associated with positive emotions, and there have been inconsistent results in the studies in particular areas, which may be due to methodological issues.
Some of these findings are consistent with other research and theories. For example, in a neuroimaging study of how individuals with psychopathy respond to emotional words, widespread differences in activation patterns have been shown across the temporal lobe when psychopathic criminals were compared to "normal" volunteers, which is consistent with views in clinical psychology. Additionally, the notion of psychopathy being characterized by low fear is consistent with findings of abnormalities in the amygdala, since deficits in aversive conditioning and instrumental learning are thought to result from amygdala dysfunction, potentially compounded by orbitofrontal cortex dysfunction, although the specific reasons are unknown.
Proponents of the primary-secondary psychopathy distinction and triarchic model argue that there are neurological differences between these subgroups of psychopathy which support their views. For instance, the boldness factor in the triarchic model is argued to be associated with reduced activity in the amygdala during fearful or aversive stimuli and reduced startle response, while the disinhibition factor is argued to be associated with impairment of frontal lobe tasks. There is evidence that boldness and disinhibition are genetically distinguishable.
High levels of testosterone combined with low levels of cortisol and/or serotonin have been theorized as contributing factors. Testosterone is "associated with approach-related behavior, reward sensitivity, and fear reduction", and injecting testosterone "shift[s] the balance from punishment to reward sensitivity", decreases fearfulness, and increases "responding to angry faces". Some studies have found that high testosterone levels are associated with antisocial and aggressive behaviors, yet other research suggests that testosterone alone does not cause aggression but increases dominance-seeking. It is unclear from studies if psychopathy correlates with high testosterone levels, but a few studies have found psychopathy to be linked to low cortisol levels and reactivity. Cortisol increases withdrawal behavior and sensitivity to punishment and aversive conditioning, which are abnormally low in individuals with psychopathy and may underlie their impaired aversion learning and disinhibited behavior. High testosterone levels combined with low serotonin levels are associated with "impulsive and highly negative reactions", and may increase violent aggression when an individual is provoked or becomes frustrated. Several animal studies note the role of serotonergic functioning in impulsive aggression and antisocial behavior.
However, some studies on animal and human subjects have suggested that the emotional-interpersonal traits and predatory aggression of psychopathy, in contrast to impulsive and reactive aggression, is related to increased serotoninergic functioning. A study by Dolan and Anderson on the relationship between setotonin and psychopathic traits in a sample of personality disordered offenders, found that serotonin functioning as measured by prolactin response, while inversely associated with impulsive and antisocial traits, were positively correlated with arrogant and deceitful traits, and, to a lesser extent, callous and remorseless traits. Bariş Yildirim theorizes that the 5-HTTLPR "long" allele, which is generally regarded as protective against internalizing disorders, may interact with other serotoninergic genes to create a hyper-regulation and dampening of affective processes that results in psychopathy's emotional impairments. Furthermore, the combination of the 5-HTTLPR long allele and high testosterone levels has been found to result in a reduced response to threat as measured by cortisol reactivity, which mirrors the fear deficits found in those afflicted with psychopathy.
Studies have suggested other correlations. Psychopathy was associated in two studies with an increased ratio of HVA (a dopamine metabolite) to 5-HIAA (a serotonin metabolite). Studies have found that individuals with the traits meeting criteria for psychopathy show a greater dopamine response to potential "rewards" such as monetary promises or taking drugs such as amphetamines. This has been theoretically linked to increased impulsivity. A 2010 British study found that a large 2D:4D digit ratio, an indication of high prenatal estrogen exposure, was a "positive correlate of psychopathy in females, and a positive correlate of callous affect (psychopathy sub-scale) in males".
Findings have also shown monoamine oxidase A to affect the predictive ability of the PCL-R. Monoamine oxidases (MAOs) are enzymes that are involved in the breakdown of neurotransmitters such as serotonin and dopamine and are, therefore, capable of influencing feelings, mood, and behavior in individuals. Findings suggest that further research is needed in this area.
Psychopathy is most commonly assessed with the Psychopathy Checklist, Revised (PCL-R), created by Robert D. Hare based on Cleckley's criteria from the 1940s, criminological concepts such as those of William and Joan McCord, and his own research on criminals and incarcerated offenders in Canada. The PCL-R is widely used and is referred to by some as the "gold standard" for assessing psychopathy. There are nonetheless numerous criticisms of the PCL-R as a theoretical tool and in real-world usage.
Each of the 20 items in the PCL-R is scored on a three-point scale, with a rating of 0 if it does not apply at all, 1 if there is a partial match or mixed information, and 2 if there is a reasonably good match to the offender. Assessment is ideally done through face-to-face interviews together with supporting information on subject history (e.g. from case files), but can also be conducted using only on-file information. It can take up to three hours to collect and review the information. High PCL-R scores are positively associated with measures of impulsivity and aggression, Machiavellianism, and persistent criminal behavior, and are negatively associated with measures of empathy and affiliation. Out of a maximum score of 40, the cut-off for the label of psychopathy is 30 in the United States and 25 in the United Kingdom. A cut-off score of 25 is also sometimes used for research purposes.
Most of the PCL-R items are grouped into two categories, each measuring a certain aspect of psychopathy. Factor 1 measures affective (emotion) deficits and interpersonal traits and is associated with narcissism, reduced empathy, boldness as well as reduced fear or depression. Factor 2 measures impulsive, irresponsible and antisocial behaviors and is associated with a maladaptive lifestyle including criminality. The two factors correlate with each other to some extent. The items "promiscuous sexual behavior" and "many short-term marital relationships" are not associated with either factor.
Because scores may have important consequences for an individual's future, there is a considerable potential for harm if the checklist is used or administered incorrectly. Results can only be considered valid if the test is administered by a suitably qualified and experienced clinician under controlled conditions.
There are additional inventories derived directly from the PCL-R, including the Psychopathy Checklist: Screening Version (PCL:SV) and Psychopathy Checklist: Youth Version (PCL:YV). The PCL:SV was developed as a labor-saving assessment for the same forensic settings as the PCL-R and to meet the needs of settings where clients do not necessarily have criminal records (e.g. civil psychiatric patients). The PCL:YV assesses juvenile psychopathy in children and adolescents.
Psychopathic Personality Inventory
Unlike the PCL, the Psychopathic Personality Inventory (PPI) was developed to comprehensively index personality traits without explicitly referring to antisocial or criminal behaviors themselves. It is a self-report scale that was developed originally for non-clinical samples (e.g. university students) rather than prisoners, though may be used with the latter. It was revised in 2005 to become the PPI-R and now comprises 154 items organized into eight subscales. The item scores have been found to group into two overarching and largely separate factors (unlike the PCL-R factors), Fearless-Dominance and Impulsive Antisociality, plus a third factor, Coldheartedness, which is largely dependent on scores on the other two. Factor 1 is associated with social efficacy while Factor 2 is associated with maladaptive tendencies. A person may score at different levels on the different factors, but the overall score indicates the extent of psychopathic personality.
DSM and ICD
There are currently two widely established systems for classifying mental disorders—the International Classification of Diseases (ICD) produced by the World Health Organization (WHO) and the Diagnostic and Statistical Manual of Mental Disorders (DSM) produced by the American Psychiatric Association (APA). Both list categories of disorders thought to be distinct types, and have deliberately converged their codes in recent revisions so that the manuals are often broadly comparable, although significant differences remain.
The first edition of the DSM in 1952 had a section on sociopathic personality disturbances, then a general term that included such things as homosexuality and alcoholism as well as an "antisocial reaction" and "dyssocial reaction". The latter two eventually became antisocial personality disorder (ASPD) in the DSM and dissocial personality disorder in the ICD. Both manuals have stated that their diagnoses have been referred to, or include what is referred to, as psychopathy or sociopathy, although neither diagnostic manual has ever included a disorder officially titled as such.
Antisocial personality disorder (ASPD), the criteria of which were based on American psychiatrist Hervey Cleckley's work on psychopathy, is described in the DSM-IV-TR as "... a pervasive pattern of disregard for, and violation of, the rights of others that begins in childhood or early adolescence and continues into adulthood. This pattern has also been referred to as psychopathy, sociopathy, or dissocial personality disorder".
A diagnosis of ASPD is based largely on explicit behavioral patterns, whereas measurement tools such as the PCL or PPI also largely, or solely, rely on judgment or self-reports of personality traits. The diagnostic criteria for ASPD focus relatively less on personality traits partly due to the belief that such traits are difficult to measure reliably and it is "easier to agree on the behaviors that typify a disorder than on the reasons why they occur". As a result, critics have argued that psychopathy and ASPD are not synonymous, despite the DSM's statement that ASPD has been referred to as psychopathy.
Nonetheless, psychopathy has been proposed as a specifier under an alternative model for ASPD. In the DSM-5, under "Alternative DSM-5 Model for Personality Disorders", ASPD with psychopathic features is described as characterized by "a lack of anxiety or fear and by a bold interpersonal style that may mask maladaptive behaviors (e.g., fraudulence)". Low levels of withdrawal and high levels of attention-seeking combined with low anxiety are associated with "social potency" and "stress immunity" in psychopathy.:765 Under the specifier, affective and interpersonal characteristics are comparatively emphasized over behavioral components.
The ICD defines a conceptually similar or equivalent disorder to ASPD called dissocial personality disorder, "usually coming to attention because of a gross disparity between behaviour and the prevailing social norms, and characterized by" at least 3 of 6 specific issues. The manual states that its diagnosis includes "amoral, antisocial, asocial, psychopathic, and sociopathic personality (disorder)".
There are some traditional personality tests that contain subscales relating to psychopathy, though they assess relatively non-specific tendencies towards antisocial or criminal behavior. These include the Minnesota Multiphasic Personality Inventory (Psychopathic Deviate scale), California Psychological Inventory (Socialization scale), and Millon Clinical Multiaxial Inventory Antisocial Personality Disorder scale. There is also the Levenson Self-Report Psychopathy Scale (LSRP) and the Hare Self-Report Psychopathy Scale (HSRP), but in terms of self-report tests, the PPI/PPI-R has become more used than either of these in modern psychopathy research on adults.
As with other mental disorders, psychopathy as a personality disorder may be present with a variety of other diagnosable conditions. Studies especially suggest strong comorbidity with antisocial personality disorder. Among numerous studies, positive correlations have also been reported between psychopathy and histrionic, narcissistic, borderline, paranoid, and schizoid personality disorders, panic and obsessive–compulsive disorders, but not neurotic disorders in general, schizophrenia, or depression.
Attention deficit hyperactivity disorder (ADHD) is known to be highly comorbid with conduct disorder (a theorized precursor to ASPD), and may also co-occur with psychopathic tendencies. This may be explained in part by deficits in executive function. Anxiety disorders often co-occur with ASPD, and contrary to assumptions, psychopathy can sometimes be marked by anxiety; this appears to be related to items from Factor 2 but not Factor 1 of the PCL-R. Psychopathy is also associated with substance use disorders.
It has been suggested that psychopathy may be comorbid with several other conditions than these, but limited work on comorbidity has been carried out. This may be partly due to difficulties in using inpatient groups from certain institutions to assess comorbidity, owing to the likelihood of some bias in sample selection.
Primary and secondary subtypes
Several researchers have argued that there are two variants, or subtypes, of psychopathy. There is also empirical support for separating persons scoring high on the PCL-R into two groups that do not simply reflect Factor 1 and Factor 2. There is at least preliminary evidence of differences regarding cognition and affect as measured in laboratory tests. Different theories characterize these two variants somewhat differently.
Compared to "primary" psychopathy, "secondary" psychopathy has been conceptualized as being associated with more fear, anxiety, and other negative emotions. This subtype is seen as more impulsive and with more reactive anger and aggression. David T. Lykken, using Gray's biopsychological theory of personality, argued that primary psychopathy is characterized by little fear while secondary psychopathy is characterized by an increased sensitivity to rewards. Studies also suggest that secondary psychopathy manifests more features of borderline personality than primary psychopathy, and comparable levels of antisocial behavior.
There are also different theories as to the predominant causes of either variant. Some researchers, such as Benjamin Karpman, believe that primary psychopathy is caused by an emotional deficit and that secondary psychopathy is acquired through adverse environmental experiences, although others, such as Lykken, link both variants to different biological predispositions. Some preliminary research suggests that secondary psychopathy may be associated with a more abusive childhood, a higher risk of future violence, and potentially a better response to treatment.
Research on psychopathy has largely been done on men and the PCL-R was developed using mainly male criminal samples, raising the question of how well the results apply to women. Men score higher than women on both the PCL-R and the PPI and on both of their main scales. The differences tend to be somewhat larger on the interpersonal-affective scale than on the antisocial scale. Most but not all studies have found broadly similar factor structure for men and women.
Many associations with other personality traits are similar, although in one study the antisocial factor was more strongly related with impulsivity in men and more strongly related with openness to experience in women. It has been suggested that psychopathy in men manifest more as an antisocial pattern while in women it manifests more as a histrionic pattern. Studies on this have shown mixed results. PCL-R scores may be somewhat less predictive of violence and recidivism in women. On the other hand, psychopathy may have a stronger relationship with suicide and possibly internalizing symptoms in women. A suggestion is that psychopathy manifests more as externalizing behaviors in men and more as internalizing behaviors in women.
Studies have also found that women in prison score significantly lower on psychopathy than men, with one study reporting only 11 percent of violent females in prison met the psychopathy criteria in comparison to 31 percent of violent males. Other studies have also pointed out that high psychopathic females are rare in forensic settings.
Psychopathy has often been considered untreatable. Its unique characteristics makes it among the most refractory of personality disorders, a class of mental illnesses that are already traditionally considered difficult to treat. People afflicted with psychopathy are generally unmotivated to seek treatment for their condition, and can be uncooperative in therapy. Attempts to treat psychopathy with the current tools available to psychiatry have been disappointing. Harris and Rice's Handbook of Psychopathy says that there is currently little evidence for a cure or effective treatment for psychopathy; as of yet, no pharmacological therapies are known to or have been trialed for alleviating the emotional, interpersonal and moral deficits of psychopathy, and patients with psychopathy who undergo psychotherapy might gain the skills to become more adept at the manipulation and deception of others and be more likely to commit crime. Some studies suggest that punishment and behavior modification techniques are ineffective at modifying the behavior of psychopathic individuals as they are insensitive to punishment or threat. These failures have led to a widely pessimistic view on its treatment prospects, a view that is exacerbated by the little research being done into this disorder compared to the efforts committed to other mental illnesses, which makes it more difficult to gain the understanding of this condition that is necessary to develop effective therapies.
Although the core character deficits of highly psychopathic individuals are likely to be highly incorrigible to the currently available treatment methods, the antisocial and criminal behavior associated with it may be more amenable to management, the management of which being the main aim of therapy programs in correctional settings. It has been suggested that the treatments that may be most likely to be effective at reducing overt antisocial and criminal behavior are those that focus on self-interest, emphasizing the tangible, material value of prosocial behavior, with interventions that develop skills to obtain what the patient wants out of life in prosocial rather than antisocial ways. To this end, various therapies have been tried with the aim of reducing the criminal activity of incarcerated offenders with psychopathy, with mixed success. As psychopathic individuals are insensitive to sanction, reward-based management, in which small privileges are granted in exchange for good behavior, has been suggested and used to manage their behavior in institutional settings.
Psychiatric medications may also alleviate co-occurring conditions sometimes associated with the disorder or with symptoms such as aggression or impulsivity, including antipsychotic, antidepressant or mood-stabilizing medications, although none have yet been approved by the FDA for this purpose. For example, a study found that the antipsychotic clozapine may be effective in reducing various behavioral dysfunctions in a sample of high-security hospital inpatients with antisocial personality disorder and psychopathic traits. However, research into the pharmacological treatment of psychopathy and the related condition antisocial personality disorder is minimal, with much of the knowledge in this area being extrapolations based on what is known about pharmacology in other mental disorders.
The PCL-R, the PCL:SV, and the PCL:YV are highly regarded and widely used in criminal justice settings, particularly in North America. They may be used for risk assessment and for assessing treatment potential and be used as part of the decisions regarding bail, sentence, which prison to use, parole, and regarding whether a youth should be tried as a juvenile or as an adult. There have been several criticisms against its use in legal settings. They include the general criticisms against the PCL-R, the availability of other risk assessment tools which may have advantages, and the excessive pessimism surrounding the prognosis and treatment possibilities of those who are diagnosed with psychopathy.
The interrater reliability of the PCL-R can be high when used carefully in research but tend to be poor in applied settings. In particular Factor 1 items are somewhat subjective. In sexually violent predator cases the PCL-R scores given by prosecution experts were consistently higher than those given by defense experts in one study. The scoring may also be influenced by other differences between raters. In one study it was estimated that of the PCL-R variance, about 45% was due to true offender differences, 20% was due to which side the rater testified for, and 30% was due to other rater differences.
To aid a criminal investigation, certain interrogation approaches may be used to exploit and leverage the personality traits of suspects thought to have psychopathy and make them more likely to divulge information.
In the United Kingdom, "psychopathic disorder" was legally defined in the Mental Health Act (UK), under MHA1983, as "a persistent disorder or disability of mind (whether or not including significant impairment of intelligence) which results in abnormally aggressive or seriously irresponsible conduct on the part of the person concerned". This term was intended to reflect the presence of a personality disorder in terms of conditions for detention under the Mental Health Act 1983. Amendments to MHA1983 within the Mental Health Act 2007 abolished the term "psychopathic disorder", with all conditions for detention (e.g. mental illness, personality disorder, etc.) encompassed by the generic term of "mental disorder".
In England and Wales, the diagnosis of dissocial personality disorder is grounds for detention in secure psychiatric hospitals under the Mental Health Act if they have committed serious crimes, but since such individuals are disruptive to other patients and not responsive to usual treatment methods this alternative to traditional incarceration is often not used.
"Sexual psychopath" laws
Starting in the 1930s, before some modern concepts of psychopathy were developed, "sexual psychopath" laws, the term referring broadly to mental illness, were introduced by some states, and by the mid-1960s more than half of the states had such laws. Sexual offenses were considered to be caused by underlying mental illnesses, and it was thought that sex offenders should be treated, in agreement with the general rehabilitative trends at this time. Courts committed sex offenders to a mental health facility for community protection and treatment.
Starting in 1970, many of these laws were modified or abolished in favor of more traditional responses such as imprisonment due to criticism of the "sexual psychopath" concept as lacking scientific evidence, the treatment being ineffective, and predictions of future offending being dubious. There were also a series of cases where persons treated and released committed new sexual offenses. Starting in the 1990s, several states have passed sexually dangerous person laws, including registration, housing restrictions, public notification, mandatory reporting by health care professionals, and civil commitment, which permits indefinite confinement after a sentence has been completed. Psychopathy measurements may be used in the confinement decision process.
The prognosis for psychopathy in forensic and clinical settings is quite poor, with some studies reporting that treatment may worsen the antisocial aspects of psychopathy as measured by recidivism rates, though it is noted that one of the frequently cited studies finding increased criminal recidivism after treatment, a 2011 retrospective study of a treatment program in the 1960s, had several serious methodological problems and likely would not be approved of today. However, some relatively rigorous quasi-experimental studies using more modern treatment methods have found improvements regarding reducing future violent and other criminal behavior, regardless of PCL-R scores, although none were randomized controlled trials. Various other studies have found improvements in risk factors for crime such as substance abuse. No study has of yet in a 2013 review examined if the personality traits that form the core character disturbances of psychopathy could be changed by such treatments.
A 2008 study using the PCL:SV found that 1.2% of a US sample scored 13 or more out of 24, indicating "potential psychopathy". The scores correlated significantly with violence, alcohol use, and lower intelligence. A 2009 British study by Coid et al., also using the PCL:SV, reported a community prevalence of 0.6% scoring 13 or more. The scores correlated with younger age, male gender, suicide attempts, violence, imprisonment, homelessness, drug dependence, personality disorders (histrionic, borderline and antisocial), and panic and obsessive–compulsive disorders.
Psychopathy has a much higher prevalence in the convicted and incarcerated population, where it is thought that an estimated 15–25% of prisoners qualify for the diagnosis. A study on a sample of inmates in the UK found that 7.7% of the inmates interviewed met the PCL-R cut-off of 30 for a diagnosis of psychopathy. A study on a sample of inmates in Iran using the PCL:SV found a prevalence of 23% scoring 18 or more.
Society and culture
In the workplace
There is limited research on psychopathy in the general work populace, in part because the PCL-R includes antisocial behavior as a significant core factor (obtaining a PCL-R score above the threshold is unlikely without having significant scores on the antisocial-lifestyle factor) and does not include positive adjustment characteristics, and most researchers have studied psychopathy in incarcerated criminals, a relatively accessible population of research subjects. However, psychologists Fritzon and Board, in their study comparing the incidence of personality disorders in business executives against criminals detained in a mental hospital, found that the profiles of some senior business managers contained significant elements of personality disorders, including those referred to as the "emotional components", or interpersonal-affective traits, of psychopathy. Factors such as boldness, low disinhibition, and meanness as defined in the triarchic model, in combination with other advantages such as a favorable upbringing and high intelligence, are thought to correlate with stress immunity and stability, and may contribute to this particular expression. Such individuals are sometimes referred to as "successful psychopaths" or "corporate psychopaths" (among other synonyms), and may not have extensive histories of traditional criminal or antisocial behavior as characteristic of the traditional conceptualization of psychopathy. Robert Hare claims that the prevalence of psychopathic traits is higher in the business world than in the general population, reporting that while about 1% of the general population meet the clinical criteria for psychopathy, figures of around 3-4% have been cited for more senior positions in business.
Academics on this subject believe that although psychopathy is manifested in only a small percentage of workplace staff, it is more common at higher levels of corporate organizations, and its negative effects (for example, increased bullying, conflict, stress, staff turnover, absenteeism, reduction in productivity) often causes a ripple effect throughout an organization, setting the tone for an entire corporate culture. Employees with the disorder are self-serving opportunists, and may disadvantage their own organizations to further their own interests. They may be charming to staff above his/her level in the workplace hierarchy, aiding their ascent through the organization, but abusive to staff below his/her level, and can do enormous damage when they are positioned in senior management roles. Psychopathy as measured by the PCL-R is associated with lower performance appraisals among corporate professionals. The psychologist Oliver James identifies psychopathy as one of the dark triadic traits in the workplace, the others being narcissism and Machiavellianism, which, like psychopathy, can have negative consequences.
Characters with psychopathy or sociopathy are some of the most notorious characters in film and literature, but their characterizations may only vaguely or partly relate to the concept of psychopathy as it is defined in psychiatry, criminology, and research. The character may be identified as having psychopathy within the fictional work itself, by its creators, or from the opinions of audiences and critics, and may be based on undefined popular stereotypes of psychopathy.
Such characters are often portrayed in an exaggerated fashion and typically in the role of a villain or antihero, where the general characteristics and stereotypes associated with psychopathy are useful to facilitate conflict and danger. Because the definitions, criteria, and popular conceptions throughout its history have varied over the years and continue to change even now, many of the characters characterized as psychopathic in notable works at the time of publication may no longer fit the current definition and conception of psychopathy. There are several archetypal images of psychopathy in both lay and professional accounts which only partly overlap and can involve contradictory traits: the charming con artist, the deranged serial killer and mass murderer, the callous and scheming businessperson, and the chronic low-level offender and juvenile delinquent. The public concept reflects some combination of fear of a mythical bogeyman, the disgust and intrigue surrounding evil, and fascination and sometimes perhaps envy of people who might appear to go through life without attachments and unencumbered by guilt, anguish or insecurity.
The word psychopathy is a joining of the Greek words psyche (ψυχή) "soul" and pathos (πάθος) "suffering, feeling". The first documented use is from 1847 in Germany as psychopatisch, and the noun psychopath has been traced to 1885. In medicine, patho- has a more specific meaning of disease (thus pathology has meant the study of disease since 1610, and psychopathology has meant the study of mental disorder in general since 1847. A sense of "a subject of pathology, morbid, excessive" is attested from 1845, including the phrase pathological liar from 1891 in the medical literature).
The term psychopathy initially had a very general meaning referring to all sorts of mental disorders and social aberrations, popularised from 1891 in Germany by Koch's concept of "psychopathic inferiority" (psychopathische Minderwertigkeiten). Some medical dictionaries still define psychopathy in both a narrow and broad sense, such as MedlinePlus from the U.S. National Library of Medicine. On the other hand, Stedman's Medical Dictionary defines psychopathy only as an outdated term for an antisocial type of personality disorder.
The term psychosis was also used in Germany from 1841, originally in a very general sense. The suffix -ωσις (-osis) meant in this case "abnormal condition". This term or its adjective psychotic would come to refer to the more severe mental disturbances and then specifically to mental states or disorders characterized by hallucinations, delusions or in some other sense markedly out of touch with reality.
The slang term psycho has been traced to a shortening of the adjective psychopathic from 1936, and from 1942 as a shortening of the noun psychopath, but it is also used as shorthand for psychotic or crazed.
The label psychopath has been described as nonspecific but probably persisting because it indicates that the source of behavior lies in the psyche rather than in the situation. The media usually uses the term to designate any criminal whose offenses are particularly abhorrent and unnatural, but that is not its original or general psychiatric meaning.
The word element socio has been used in compound words since around 1880. The term sociopathy may have been first introduced in 1909 in Germany by biological psychiatrist Karl Birnbaum and in 1930 in the US by educational psychologist George E. Partridge, as an alternative to the concept of psychopathy. It was used to indicate that the defining feature is violation of social norms, or antisocial behavior, and has often also been associated with postulating social as well as biological causation.
There are various contemporary usages of the term. Robert Hare stated in the popular science book entitled Snakes in Suits that sociopathy and psychopathy are often used interchangeably, but in some cases the term sociopathy is preferred because it is less likely than is psychopathy to be confused with psychosis, whereas in other cases the two terms may be used with different meanings that reflect the user's views on the origins and determinants of the disorder. Hare contended that the term sociopathy is preferred by those that see the causes as due to social factors and early environment, and the term psychopathy preferred by those who believe that there are psychological, biological, and genetic factors involved in addition to environmental factors. Hare also provides his own definitions: he describes psychopathy as not having a sense of empathy or morality, but sociopathy as only differing in sense of right and wrong from the average person.
The concept of psychopathy has been indirectly connected to the early 19th century with the work of Pinel (1801; "mania without delirium") and Pritchard (1835; "moral insanity"), although historians have largely discredited the idea of a direct equivalence. Psychopathy originally described any illness of the mind, but found its application to a narrow subset of mental conditions when was used toward the end of the 19th century by the German psychiatrist Julius Koch (1891) to describe various behavioral and moral dysfunction in the absence of an obvious mental illness or intellectual disability. He applied the term psychopathic inferiority (psychopathischen Minderwertigkeiten) to various chronic conditions and character disorders, and his work would influence the later conception of the personality disorder.
The term psychopathic came to be used to describe a diverse range of dysfunctional or antisocial behavior and mental and sexual deviances, including at the time homosexuality. It was often used to imply an underlying "constitutional" or genetic origin. Disparate early descriptions likely set the stage for modern controversies about the definition of psychopathy.
An influential figure in shaping modern American conceptualizations of psychopathy was American psychiatrist Hervey Cleckley. In his classic monograph, The Mask of Sanity (1941), Cleckley drew on a small series of vivid case studies of psychiatric patients at a Veterans Administration hospital in Georgia to describe the disorder. Cleckley used the metaphor of the "mask" to refer to the tendency of psychopaths to appear confident, personable, and well-adjusted compared to most psychiatric patients, while revealing underlying pathology through their actions over time. Cleckley formulated sixteen criteria to describe the disorder. The Scottish psychiatrist David Henderson had also been influential in Europe from 1939 in narrowing the diagnosis.
The diagnostic category of sociopathic personality in early editions of the Diagnostic and Statistical Manual (DSM) had some key similarities to Cleckley's ideas, though in 1980 when renamed Antisocial Personality Disorder some of the underlying personality assumptions were removed. In 1980, Canadian psychologist Robert D. Hare introduced an alternative measure, the "Psychopathy Checklist" (PCL) based largely on Cleckley's criteria, which was revised in 1991 (PCL-R), and is the most widely used measure of psychopathy. There are also several self-report tests, with the Psychopathic Personality Inventory (PPI) used more often among these in contemporary adult research.
Famous individuals have sometimes been diagnosed, albeit at a distance, as psychopaths. As one example out of many possible from history, in a 1972 version of a secret report originally prepared for the Office of Strategic Services in 1943, and which may have been intended to be used as propaganda, non-medical psychoanalyst Walter C. Langer suggested Adolf Hitler was probably a psychopath. However, others have not drawn this conclusion; clinical forensic psychologist Glenn Walters argues that Hitler's actions do not warrant a diagnosis of psychopathy as, although he showed several characteristics of criminality, he was not always egocentric, callously disregarding of feelings or lacking impulse control, and there is no proof he couldn't learn from mistakes.
- Skeem, J. L.; Polaschek, D. L. L.; Patrick, C. J.; Lilienfeld, S. O. (2011). "Psychopathic Personality: Bridging the Gap Between Scientific Evidence and Public Policy". Psychological Science in the Public Interest 12 (3): 95–162. doi:10.1177/1529100611426706.
- Current Conceptions of Psychopathic Personality G. E. Partridge, The American Journal of Psychiatry. 1930 July ; 1(87):53-99
- Patrick, Christopher (2005). Handbook of Psychopathy. Guilford Press. ISBN 978-1-60623-804-2.[page needed]
- Andrade, Joel (23 Mar 2009). Handbook of Violence Risk Assessment and Treatment: New Approaches for Mental Health Professionals. New York, NY: Springer Publishing Company. ISBN 978-0-8261-9904-1. Retrieved January 5, 2014.
- "Hare Psychopathy Checklist". Encyclopedia of Mental Disorders. Retrieved September 4, 2013.
- Delisi, Matt; Vaughn, Michael G.; Beaver, Kevin M.; Wright, John Paul (2009). "The Hannibal Lecter Myth: Psychopathy and Verbal Intelligence in the MacArthur Violence Risk Assessment Study". Journal of Psychopathology and Behavioral Assessment 32 (2): 169–77. doi:10.1007/s10862-009-9147-z.
- Patrick, Christopher; Fowles, Don; Krueger, Robert (August 2009). "Triarchic conceptualization of psychopathy: Developmental origins of disinhibition, boldness, and meanness". Development and Psychopathology (Cambridge University Press) 21 (3): 913–938. doi:10.1017/S0954579409000492. PMID 19583890. Retrieved January 6, 2014.
- Harris, Grant T.; Rice, Marnie E.; Quinsey, Vernon L. (1994). "Psychopathy as a taxon: Evidence that psychopaths are a discrete class". Journal of Consulting and Clinical Psychology 62 (2): 387–97. doi:10.1037/0022-006X.62.2.387. PMID 8201078.
- Marcus, David K.; John, Siji L.; Edens, John F. (2004). "A Taxometric Analysis of Psychopathic Personality". Journal of Abnormal Psychology 113 (4): 626–35. doi:10.1037/0021-843X.113.4.626. PMID 15535794.
- The term "psychopath" may be used in research without sufficient clarification on whether the intended meaning of the term in context is someone who is "relatively psychopathic" in this manner. Therefore it is important to note that where "psychopath" is used elsewhere in this article, it implies only the meaning intended by any authors referenced, which may not necessarily entail someone that is psychopathic relative to others along a continuum.
- Edens, John F.; Marcus, David K.; Lilienfeld, Scott O.; Poythress Jr, Norman G. (2006). "Psychopathic, Not Psychopath: Taxometric Evidence for the Dimensional Structure of Psychopathy". Journal of Abnormal Psychology 115 (1): 131–44. doi:10.1037/0021-843X.115.1.131. PMID 16492104.
- Widiger, Thomas A.; Lynam, Donald R. (2002). "Psychopathy and the Five-Factor Model of Personality". In Millon, Theodore; Simonsen, Erik; Birket-Smith, Morten; et al. Psychopathy: Antisocial, Criminal, and Violent Behavior. New York: Guilford Press. pp. 171–87. ISBN 978-1-57230-864-0.
- Zuckerman, Marvin (1991). Psychobiology of personality. Cambridge University Press. p. 390. ISBN 0-521-35942-2.
- Otto F., Kernberg (2004). Aggressivity, Narcissism, and Self-Destructiveness in the Psychotherapeutic Relationship: New Developments in the Psychopathology and Psychotherapy of Severe Personality Disorders. Yale University Press. ISBN 0-300-10180-5.[page needed]
- Robert M. Regoli; John D. Hewitt; Matt DeLisi (20 April 2011). Delinquency in Society: The Essentials. Jones & Bartlett Learning. p. 99. ISBN 978-0-7637-7790-6.
- W. Keith Campbell; Joshua D. Miller (7 July 2011). The Handbook of Narcissism and Narcissistic Personality Disorder: Theoretical Approaches, Empirical Findings, and Treatments. John Wiley & Sons. p. 154. ISBN 978-1-118-02924-4.
- Mark R. Leary; Rick H. Hoyle (5 June 2009). Handbook of individual differences in social behavior. Guilford Press. p. 100. ISBN 978-1-59385-647-2.
- Jones, D. N., Paulhus, D. L. (2010). "Differentiating the Dark Triad within the interpersonal circumplex". In Horowitz, L.; nbsp; M., Strack, S.; nbsp; N. Handbook of interpersonal theory and research. New York: Guilford. pp. 249–67.
- Chabrol H.; Van Leeuwen N.; Rodgers R.; Sejourne N. (2009). "Contributions of psychopathic, narcissistic, Machiavellian, and sadistic personality traits to juvenile delinquency". Personality and Individual Differences 47 (7): 734–739. doi:10.1016/j.paid.2009.06.020.
- Buckels, E. E.; Jones, D. N.; Paulhus, D. L. (2013). "Behavioral confirmation of everyday sadism". Psychological Science 24 (11): 2201–9. doi:10.1177/0956797613490749. PMID 24022650.
- de Almeida, Rosa Maria Martins; Cabral, João Carlos Centurion; Narvaes, Rodrigo. "Behavioural, hormonal and neurobiological mechanisms of aggressive behaviour in human and nonhuman primates". Physiology & Behavior 143: 121–135. doi:10.1016/j.physbeh.2015.02.053.
- Patrick, Christopher J, ed. (2005). Handbook of Psychopathy. Guilford Press. pp. 440–3.
- Coid, Jeremy; Yang, Min; Ullrich, Simone; Roberts, Amanda; Moran, Paul; Bebbington, Paul; Brugha, Traolach; Jenkins, Rachel; Farrell, Michael; Lewis, Glyn; Singleton, Nicola; Hare, Robert (May 2009). "Psychopathy among prisoners in England and Wales". International Journal of Law and Psychiatry (Elsevier Ltd) 32 (3): 134–41. doi:10.1016/j.ijlp.2009.02.008. PMID 19345418. Retrieved 1 April 2016.
- The Trouble with Psychopathy as a General Theory of Crime Glenn D. Walters. Int J Offender Ther Comp Criminol April 2004 vol. 48 no. 2 133–148, doi 10.1177/0306624X03259472 PMID 15070462
- Neumann, Craig S.; Hare, Robert D. (2008). "Psychopathic traits in a large community sample: Links to violence, alcohol use, and intelligence" (PDF). Journal of Consulting and Clinical Psychology 76 (5): 893–9. doi:10.1037/0022-006X.76.5.893. PMID 18837606.
- Glenn, Andrea L.; Raine, Adrian (July 2009). "Psychopathy and instrumental aggression: Evolutionary, neurobiological, and legal perspectives". International Journal of Law and Psychiatry (Elsevier Ltd) 32 (4): 253–258. doi:10.1016/j.ijlp.2009.04.002. ISSN 0160-2527. PMID 19409615. Retrieved 8 April 2016.
- Walsh, Zach; Swogger, Marc T.; Walsh, Tiffany; Kosson, David S. (December 2007). "Psychopathy and violence: increasing specificity". Netherlands journal of psychology 63 (4): 125–132. doi:10.1007/BF03061075.
- Woodworth, Michael; Porter, Stephen (2002). "In cold blood: Characteristics of criminal homicides as a function of psychopathy". Journal of Abnormal Psychology 111 (3): 436–45. doi:10.1037/0021-843X.111.3.436. PMID 12150419.
- Heilbrun, Kirk (2005). "Violence Risk: From Prediction to Management". In Carson, David; Bull, Ray. Handbook of Psychology in Legal Contexts. pp. 127–42. doi:10.1002/0470013397.ch5. ISBN 978-0-470-01339-7.
- Mills, Jeremy F.; Kroner, Daryl G.; Morgan, Robert D. "Psychopathic Traits". Clinician's Guide to Violence Risk Assessment. Guilford Press. pp. 55–64. ISBN 978-1-60623-985-8.
- Yang, Min; Wong, Stephen C. P.; Coid, Jeremy (2010). "The efficacy of violence prediction: A meta-analytic comparison of nine risk assessment tools". Psychological Bulletin 136 (5): 740–67. doi:10.1037/a0020473. PMID 20804235.
- Singh JP, Grann M, Fazel S (Apr 2011). "A comparative study of violence risk assessment tools: a systematic review and metaregression analysis of 68 studies involving 25,980 participants". Clin Psychol Rev. 31 (3): 499–513. doi:10.1016/j.cpr.2010.11.009. PMID 21255891.
- Violence risk meta-meta: Instrument choice does matter: Despite popularity, psychopathy test and actuarials not superior to other prediction methods Karen Franklin, Ph.D. forensic psychologist and adjunct professor, 2011
- Singh Jay P.; Grann Martin; Fazel Seena (2013). "Authorship Bias in Violence Risk Assessment? A Systematic Review and Meta-Analysis". PLoS ONE 8 (9): e72484. doi:10.1371/journal.pone.0072484.
- Morton, Robert J. "Serial Murder". Federal Bureau of Investigation. Retrieved 2011-01-01.
- Porter, Stephen; Brinke, Leanne; Wilson, Kevin (2009). "Crime profiles and conditional release performance of psychopathic and non-psychopathic sexual offenders". Legal and Criminological Psychology 14 (1): 109–18. doi:10.1348/135532508X284310.
- Williams, Kevin M.; Cooper, Barry S.; Howell, Teresa M.; Yuille, John C.; Paulhus, Delroy L. (2008). "Inferring Sexually Deviant Behavior from Corresponding Fantasies: The Role of Personality and Pornography Consumption". Criminal Justice and Behavior 36 (2): 198–22. doi:10.1177/0093854808327277.
- Porter, Stephen; Woodworth, Michael; Earle, Jeff; Drugge, Jeff; Boer, Douglas (2003). "Characteristics of sexual homicides committed by psychopathic and nonpsychopathic offenders". Law and Human Behavior 27 (5): 459–70. doi:10.1023/A:1025461421791. PMID 14593792.
- Levenson, Jill S.; Morin, John W. (2000). Treating Non-offending Parents in Child Sexual Abuse Cases. SAGE. p. 7. ISBN 0-7619-2192-3.
- Inter-rater reliability of the PCL-R total and factor scores among psychopathic sex offenders: are personality features more prone to disagreement than behavioral features? John F. Edens, Marcus T. Boccaccini, Darryl W. Johnson (2010)
- Häkkänen-Nyholm, Helinä; Nyholm, Jan-Olof, eds. (2012). Psychopathy and Law: A Practitioners Guide. John Wiley & Sons. p. 177. ISBN 978-0-470-97238-0.
- Horgan, John (2005). The Psychology of Terrorism. Routledge. p. 49. ISBN 978-0-7146-5262-7.
- Swogger, Marc T.; Walsh, Zach; Kosson, David S. (May 2007). "Domestic violence and psychopathic traits: distinguishing the antisocial batterer from other antisocial offenders". Aggressive Behavior 33 (3): 253–260. doi:10.1002/ab.20185.
- Gao, Yu; Raine, Adrian (March 2010). "Successful and unsuccessful psychopaths: a neurobiological model.". Behavioral Sciences & the Law 28 (2): 194–210. doi:10.1002/bsl.924. PMID 20422645. Retrieved 12 March 2016.
- Robert Hare. "Psychopathy Scales: PCL:YV". "Without Conscience". Retrieved January 5, 2014.
- Robert Hare. "Psychopathy Scales: APSD". "Without Conscience". Retrieved January 5, 2014.
- Hinshaw, S. P., & Lee, S. S. (2003). Conduct and oppositional defiant disorders. In E. J. Mash & R. A. Barkley (Eds.), Child psychopathology (pp. 144-198). New York: Guilford Press.
- American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders (Fifth ed.). Arlington, VA: American Psychiatric Publishing. p. 659. ISBN 978-0-89042-555-8.
- "Highlights of Changes from DSM-IV-TR to DSM-5" (PDF). DSM-5 Development. American Psychiatric Association. 2013. Retrieved January 5, 2014.
- "Protect – Watch Your Head". The Franklin Institute Online. The Franklin Institute. 2004. Retrieved July 10, 2013.
- Archives of General Psychiatry, February 1, 2000[verification needed]
- Nature Neuroscience, November 1999[verification needed]
- Blair, R.J.R (2008). "The amygdala and ventromedial prefrontal cortex: Functional contributions and dysfunction in psychopathy". Philosophical Transactions of the Royal Society B: Biological Sciences 363 (1503): 2557–65. doi:10.1098/rstb.2008.0027. PMC 2606709. PMID 18434283.
- Craig, M C; Catani, M; Deeley, Q; Latham, R; Daly, E; Kanaan, R; Picchioni, M; McGuire, P K; Fahy, T; Murphy, D G M (2009). "Altered connections on the road to psychopathy". Molecular Psychiatry 14 (10): 946–53, 907. doi:10.1038/mp.2009.40. PMID 19506560.
- Hare, Robert D.; Neumann, Craig S. (2008). "Psychopathy as a Clinical and Empirical Construct" (PDF). Annual Review of Clinical Psychology 4 (1): 217–46. doi:10.1146/annurev.clinpsy.3.022806.091452. PMID 18370617.
- Decety, J., & Skelly, L. (2013). The neural underpinnings of the experience of empathy: Lessons for psychopathy. In K. N. Ochsner and S. M. Kosslyn (Eds.), The Oxford Handbook of Cognitive Neuroscience – Volume 2 (pp. 228-243). New York: Oxford University Press.
- Kiehl K. A. (2006). "A cognitive neuroscience perspective on psychopathy: Evidence for paralimbic system dysfunction". Psychiatry Research 142 (2–3): 107–128. doi:10.1016/j.psychres.2005.09.013. PMC 2765815. PMID 16712954.
- Blair, R.J. (1995). "A cognitive developmental approach to morality: investigating the psychopath." (PDF). Cognition 57: 1–29. doi:10.1016/0010-0277(95)00676-p.
- Blair, R. J. R. (2003). "Neurobiological basis of psychopathy". The British Journal of Psychiatry 182 (1): 5–7. doi:10.1192/bjp.182.1.5. PMID 12509310.
- "Psychopathy" by Quinton 2006
- Blair, R.J.; E. Colledge, D.G. Mitchell (2001a). "Somatic markers and response reversal: is there orbitofrontal cortex dysfunction in boys with psychopathic tendencies?". Journal of Abnormal Child Psychology.
- Blair, R. J.; D.G. Mitchell, R.A. Richell; et al. (2002). "Turning a deaf ear to fear: impaired recognition of vocal affect in psychopathic individuals". Journal of Abnormal Psychology 111: 682–686. doi:10.1037/0021-843x.111.4.682.
- Stevens, D.; T. Charman, R.J. Blair (2001). "Recognition of emotion in facial expressions and vocal tones in children with psychopathic tendencies". Journal of Genetic Psychology.
- Decety L., Skelly L. R., Yoder K. J., Kiehl K.; Skelly; Yoder; Kiehl (2014). "Neural processing of dynamic facial expressions in psychopaths". Social Neuroscience 9 (1): 36–49. doi:10.1080/17470919.2013.866905. PMC 3970241. PMID 24359488.
- Dawel A., O'Kearney R., McKone E., Palermo R.; o’Kearney; McKone; Palermo (2012). "Not just fear and sadness: Meta-analytic evidence of pervasive emotion recognition deficits for facial and vocal expressions in psychopathy". Neuroscience and Biobehavioral Reviews 36 (10): 2288–2304. doi:10.1016/j.neubiorev.2012.08.006. PMID 22944264.
- Dawel, Amy; O'Kearney, Richard; McKone, Elinor; Palermo, Romina (2012-11-01). "Not just fear and sadness: meta-analytic evidence of pervasive emotion recognition deficits for facial and vocal expressions in psychopathy". Neuroscience and Biobehavioral Reviews 36 (10): 2288–2304. doi:10.1016/j.neubiorev.2012.08.006. ISSN 1873-7528. PMID 22944264.
- Meffert, H; Gazzola, V; den Boer, JA; Bartels, AA; Keysers, C (August 2013). "Reduced spontaneous but relatively normal deliberate vicarious representations in psychopathy.". Brain 136 (8): 2550–62. doi:10.1093/brain/awt190. PMID 23884812. Retrieved 12 March 2016.
- Hogenboom, Melissa (July 25, 2013). "Psychopathic criminals have empathy switch". BBC News. Retrieved July 28, 2013.
- Lewis, Tanya. "Cold-hearted Psychopaths Feel Empathy Too". Live Science. 24 July 2013.
- Decety J.; Skelly L. R.; Kiehl K. A. (2013). "Brain response to empathy-eliciting scenarios in incarcerated individuals with psychopathy". JAMA Psychiatry 70 (6): 638–645. doi:10.1001/jamapsychiatry.2013.27.
- Decety J.; Chen C.; Harenski C. L.; Kiehl K. A. (2013). "An fMRI study of affective perspective taking in individuals with psychopathy: imagining another in pain does not evoke empathy". Frontiers in Human Neuroscience 7: 489. doi:10.3389/fnhum.2013.00489.
- Baron-Cohen, Simon (2011). Zero Degrees of Empathy: A New Theory of Human Cruelty. Penguin UK. ISBN 9780713997910. Retrieved August 8, 2013.
- Koenigs, M.; Kruepke, M.; Zeier, J.; Newman, J. P. (2011). "Utilitarian moral judgment in psychopathy". Social Cognitive and Affective Neuroscience 7 (6): 708–14. doi:10.1093/scan/nsr048. PMC 3427868. PMID 21768207.
- Young, Liane; Koenigs, Michael; Kruepke, Michael; Newman, Joseph P. (2012). "Psychopathy increases perceived moral permissibility of accidents" (PDF). Journal of Abnormal Psychology 121 (3): 659–67. doi:10.1037/a0027489. PMID 22390288.
- Glenn, Andrea L.; Kurzban, Robert; Raine, Adrian (2011). "Evolutionary theory and psychopathy". Aggression and Violent Behavior 16 (5): 371–380. doi:10.1016/j.avb.2011.03.009.
- Caspi, A.; McClay, J; Moffitt, TE; Mill, J; Martin, J; Craig, IW; Taylor, A; Poulton, R (2002). "Role of Genotype in the Cycle of Violence in Maltreated Children". Science 297 (5582): 851–4. Bibcode:2002Sci...297..851C. doi:10.1126/science.1072290. PMID 12161658.
- Frazzetto, Giovanni; Di Lorenzo, Giorgio; Carola, Valeria; Proietti, Luca; Sokolowska, Ewa; Siracusano, Alberto; Gross, Cornelius; Troisi, Alfonso (2007). Baune, Bernhard, ed. "Early Trauma and Increased Risk for Physical Aggression during Adulthood: The Moderating Role of MAOA Genotype". PLoS ONE 2 (5): e486. Bibcode:2007PLoSO...2..486F. doi:10.1371/journal.pone.0000486. PMC 1872046. PMID 17534436.
- Sabol, S. Z.; Hu, Stella; Hamer, D. (1998). "A functional polymorphism in the monoamine oxidase a gene promoter". Human Genetics 103 (3): 273–9. doi:10.1007/s004390050816. PMID 9799080.
- Tikkanen, Roope; Auvinen-Lintunen, Laura; Ducci, Francesca; Sjöberg, Rickard L.; Goldman, David; Tiihonen, Jari; Ojansuu, Ilkka; Virkkunen, Matti (2011). "Psychopathy, PCL-R, and MAOA genotype as predictors of violent reconvictions". Psychiatry Research 185 (3): 382–6. doi:10.1016/j.psychres.2010.08.026. PMC 3506166. PMID 20850185.
- Beaver KM, et al. (2012). "Exploring the association between the 2-repeat allele of the MAOA gene promoter polymorphism and psychopathic personality traits, arrests, incarceration, and lifetime antisocial behavior". Personality and Individual Differences 54: 164–168. doi:10.1016/j.paid.2012.08.014.
- Lea R, Chambers G; Chambers (2007). "Monoamine oxidase, addiction, and the "warrior" gene hypothesis" (PDF). N. Z. Med. J. 120 (1250): U2441. PMID 17339897.
- Glenn, Andrea L. (January 2011). "The other allele: Exploring the long allele of the serotonin transporter gene as a potential risk factor for psychopathy: A review of the parallels in findings". Neuroscience & Biobehavioral Reviews 35: 612–620. doi:10.1016/j.neubiorev.2010.07.005. Retrieved 7 March 2016.
- Caspi, Avshalom; Hariri, Ahmad R.; Holmes, Andrew; Uher, Rudolf; Moffitt, Terrie E. (May 2010). "Genetic sensitivity to the environment: the case of the serotonin transporter gene and its implications for studying complex diseases and traits.". The American Journal of Psychiatry 167 (5): 509–27. doi:10.1176/appi.ajp.2010.09101452. PMID 20231323. Retrieved 30 March 2016.
- Wells, Jessica; Armstrong, Todd; Boutwell, Brian; Boisvert, Danielle; Flores, Shahida; Symonds, Mary; Gangitano, David (Sep 2015). "Molecular genetic underpinnings of self-control: 5-HTTLPR andself-control in a sample of inmates". Journal of Criminal Justice (Elsevier Ltd) 43 (5): 386–96. doi:10.1016/j.jcrimjus.2015.07.004. Retrieved 30 March 2016.
- Goldman, Noreen; et al. (March 2010). "The Serotonin Transporter Polymorphism (5-HTTLPR): Allelic Variation and Links with Depressive Symptoms" 27: 260–269. doi:10.1002/da.20660. PMC 2841212. PMID 20196101. Retrieved 7 March 2016.
- Sadeh, Naomi; et al. (August 2010). "Serotonin Transporter Gene Associations with Psychopathic Traits in Youth Vary as a Function of Socioeconomic Resources". Journal of Abnormal Psychology 119: 604–609. doi:10.1037/a0019709. PMC 2916190. PMID 20677849. Retrieved 7 March 2016.
- Sadeh, Naomi; et al. (February 2013). "Analysis of monoaminergic genes, childhood abuse, and dimensions of psychopathy". Jounal of Abnormal Psychology 122: 167–179. doi:10.1037/a0029866. PMID 22985017.
- Yildirim, Bariş O. (August 2013). "Systematic review, structural analysis, and new theoretical perspectives on the role of serotonin and associated genes in the etiology of psychopathy and sociopathy". Neuroscience & Biobehavioral Reviews 37: 1254–1296. doi:10.1016/j.neubiorev.2013.04.009. PMID 23644029. Retrieved 7 March 2016.
- Patrick, Christopher J, ed. (2005). Handbook of Psychopathy. Guilford Press. pp. 234, 240.
- Hare, Robert D. (1999). Without Conscience: The Disturbing World of the Psychopaths Among Us. New York: Guilford Press. ISBN 1-57230-451-0.[page needed]
- Wallisch, Pascal (November 17, 2014). "Psychopaths in our midst — what you should know". Elsevier Connect. Elsevier B.V. Retrieved 10 April 2016.
- Koenigs, Michael (2012). "The role of prefrontal cortex in psychopathy.". Reviews in the neurosciences 23 (3): 253–62. doi:10.1515/revneuro-2012-0036. PMID 22752782. Retrieved 15 March 2016.
- Karpman, B. "On the need of separating psychopathy into two distinct clinical types: the symptomatic and the idiopathic". Journal of Criminal Psychopathology (1941).
- Newman Joseph P., MacCoon Donal G., Vaughn Leah J., Sadeh Naomi; MacCoon; Vaughn; Sadeh (2005). "Validating a Distinction Between Primary and Secondary Psychopathy With Measures of Gray's BIS and BAS Constructs". Journal of Abnormal Psychology 114 (2): 319–323. doi:10.1037/0021-843X.114.2.319. PMID 15869363.
- Waldman, I.D. & Rhee, S.H. (2006). Genetic and Environmental Influences on Psychopathy and Antisocial Behavior. In Patrick, C. (Ed.) Handbook on Law & Psychopathy (pp 205-229): New York.
- Yildirim, Bariş O. (September 2015). "Clarifying the heterogeneity in psychopathic samples: Towards a newcontinuum of primary and secondary psychopathy". Aggression and Violent Behavior 24: 9–41. doi:10.1016/j.avb.2015.05.001. Retrieved 10 March 2016.
- Sörman, Karolina (2015). The Psychopathy Construct in a Swedish Context - Conceptualization and Validation of Different Assessments (PDF). Stockholm: Karolinska Institutet. p. 29. ISBN 978-91-7549-910-9. Retrieved 27 April 2016.
- Buss, David M. (2009). "How Can Evolutionary Psychology Successfully Explain Personality and Individual Differences?". Perspectives on Psychological Science 4 (4): 359–66. doi:10.1111/j.1745-6924.2009.01138.x.
- Leedom, Liane J.; Almas, Linda Hartoonian (December 2012). "Is psychopathy a disorder or an adaptation?". Frontiers in Psychology 3. doi:10.3389/fpsyg.2012.00549.
- Patrick, Christopher J. (Editor) Handbook of Psychopathy (2005). Chapter 3: Other Theoretical Models of Psychopathy, Ronald Blackburn, Page 39
- Dadds, Mark; et al. (2010). "Learning to 'talk the talk': the relationship of psychopathic traits to deficits in empathy across childhood". The Journal of Child Psychology and Psychiatry 50 (5): 599–606. doi:10.1111/j.1469-7610.2008.02058.x.
- Weber, Sabrina; Habel, Ute; Amunts, Katrin; Schneider, Frank (2008). "Structural brain abnormalities in psychopaths—a review". Behavioral Sciences & the Law 26 (1): 7–28. doi:10.1002/bsl.802. PMID 18327824.
- Pridmore, Saxby; Chambers, Amber; McArthur, Milford (2005). "Neuroimaging in psychopathy". Australian and New Zealand Journal of Psychiatry 39 (10): 856–65. doi:10.1111/j.1440-1614.2005.01679.x. PMID 16168013.
- Glenn, Andrea L.; Raine, Adrian (2008). "The Neurobiology of Psychopathy". Psychiatric Clinics of North America 31 (3): 463–75, vii. doi:10.1016/j.psc.2008.03.004. PMID 18638646.
- Beauchaine, Theodore P.; Klein, Daniel N.; Crowell, Sheila E.; Derbidge, Christina; Gatzke-Kopp, Lisa (2009). "Multifinality in the development of personality disorders: A Biology × Sex × Environment interaction model of antisocial and borderline traits". Development and Psychopathology 21 (3): 735–70. doi:10.1017/S0954579409000418. PMC 2709751. PMID 19583882.
- Gollan, Jackie K.; Lee, Royce; Coccaro, Emil F. (2005). "Developmental psychopathology and neurobiology of aggression". Development and Psychopathology 17 (4): 1151–71. doi:10.1017/S0954579405050546. PMID 16613435.
- Lee R, Coccaro ER (2007). "Neurobiology of impulsive aggression: Focus on serotonin and the orbitofrontal cortex". In Flannery DJ, Vazsonyi AT, Waldman ID. The Cambridge handbook of violent behavior and aggression. New York: Cambridge University Press. pp. 170–86. ISBN 978-0-521-60785-8.
- Van Goozen, Stephanie H. M.; Fairchild, Graeme; Snoek, Heddeke; Harold, Gordon T. (2007). "The evidence for a neurobiological model of childhood antisocial behavior". Psychological Bulletin 133 (1): 149–82. doi:10.1037/0033-2909.133.1.149. PMID 17201574.
- van de Giessen, Elsmarieke; Rosell, Daniel R.; Thompson, Judy L.; Xu, Xiaoyan; Girgis, Ragy R.; Ehrlich, Yosefa; Slifstein, Mark; Abi-Dargham, Anissa; Siever, Larry J. (November 2014). "Serotonin transporter availability in impulsive aggressive personality disordered patients: A PET study with [11C]DASB". Journal of Psychiatric Research 58: 147–154. doi:10.1016/j.jpsychires.2014.07.025. PMID 25145808.
- Line, Samantha J.; Barkus, Chris; Rawlings, Nancy; Jennings, Katie; McHugh, Stephen; Sharp, Trevor; Bannerman, David M. (December 2014). "Reduced sensitivity to both positive and negative reinforcement in mice over-expressing the 5-hydroxytryptamine transporter". European Journal of Neuroscience 40 (12): 3735–3745. doi:10.1111/ejn.12744. PMID 25283165.
- Dolan, Mairead C.; Anderson, Ian M. (1 June 2003). "The relationship between serotonergic function and the Psychopathy Checklist: Screening Version". Journal of Psychopharmacology (Oxford, England) 17 (2): 216–222. ISSN 0269-8811. PMID 12870570.
- Josephs, Robert A.; Telch, Michael J.; Hixon, J. Gregory; Evans, Jacqueline J.; Lee, Hanjoo; Knopik, Valerie S.; McGeary, John E.; Hariri, Ahmad R.; Beevers, Christopher G. (1 June 2012). "Genetic and hormonal sensitivity to threat: Testing a serotonin transporter genotype × testosterone interaction". Psychoneuroendocrinology 37 (6): 752–761. doi:10.1016/j.psyneuen.2011.09.006. ISSN 0306-4530. PMID 21978869.
- Buckholtz, Joshua W; Treadway, Michael T; Cowan, Ronald L; Woodward, Neil D; Benning, Stephen D; Li, Rui; Ansari, M Sib; Baldwin, Ronald M; Schwartzman, Ashley N; Shelby, Evan S; Smith, Clarence E; Cole, David; Kessler, Robert M; Zald, David H (2010). "Mesolimbic dopamine reward system hypersensitivity in individuals with psychopathic traits". Nature Neuroscience 13 (4): 419–21. doi:10.1038/nn.2510. PMC 2916168. PMID 20228805.
- Blanchard, Alyson; Lyons, Minna (2010). "An investigation into the relationship between digit length ratio (2D: 4D) and psychopathy". The British Journal of Forensic Practice 12 (2): 23–31. doi:10.5042/bjfp.2010.0183.
- Hook GR (2009). ""Warrior genes" and the disease of being Māori". MAI Review (2): 1–11.
- "Maori 'warrior gene' claims appalling, says geneticist". News (NZ Herald News). August 10, 2006. Retrieved 2009-01-27.
- "Scientist debunks 'warrior gene'". News (NZ Herald News). September 12, 2009. Retrieved 2009-09-11.
- Handbook of Personology and Psychopathology Stephen Strack, John Wiley & Sons, 21 Jan 2005. Chapter 15: Psychopathy as a Personality Construct (Ronald Blackburn).
- Thinking about Psychopaths and Psychopathy: Answers to Frequently Asked Questions "What are the differences between the psychopathy definitions designed by Hare and by Cleckley?" Editor: Ellsworth Lapham Fersch. iUniverse, 30 Oct 2006
- Kiehl, Kent A.; Hoffman, Morris B. (1 January 2011). "THE CRIMINAL PSYCHOPATH: HISTORY, NEUROSCIENCE, TREATMENT, AND ECONOMICS". Jurimetrics 51 (4): 355–397. ISSN 0897-1277. PMID 24944437.
- Minkel, JR (June 17, 2010). "Fear Review: Critique of Forensic Psychopathy Scale Delayed 3 Years by Threat of Lawsuit". Scientific America.
- Walters, Glenn D. (2004). "The Trouble with Psychopathy as a General Theory of Crime". International Journal of Offender Therapy and Comparative Criminology 48 (2): 133–48. doi:10.1177/0306624X03259472. PMID 15070462.
- Dorothy Otnow Lewis, MD, Catherine A. Yeager, MA, Pamela Blake, MD, Barbara Bard, PhD, and Maren Strenziok, MS Ethics Questions Raised by the Neuropsychiatric, Neuropsychological, Educational, Developmental, and Family Characteristics of 18 Juveniles Awaiting Execution in Texas J Am Acad Psychiatry Law 32:408–29, 2004
- Franklin, Karen (2011). "Psychopathy: A Rorschach test for psychologists?". Witness.[self-published source?]
- Miller, A. K.; Rufino, K. A.; Boccaccini, M. T.; Jackson, R. L.; Murrie, D. C. (2011). "On Individual Differences in Person Perception: Raters' Personality Traits Relate to Their Psychopathy Checklist-Revised Scoring Tendencies". Assessment 18 (2): 253–60. doi:10.1177/1073191111402460. PMID 21393315.
- Hare, R. D. (2003). Manual for the Revised Psychopathy Checklist (2nd ed.). Toronto, ON, Canada: Multi-Health Systems.[page needed]
- Semple, David (2005). The Oxford Handbook of Psychiatry. Oxford University Press. pp. 448–9. ISBN 0-19-852783-7.
- Hare, Robert D.; Neumann, Craig S. (2005). "The PCL-R Assessment of Psychopathy: Development, Structural Properties, and New Directions". In Patrick, Christopher J. Handbook of Psychopathy. New York: Guilford. pp. 58–88. ISBN 978-1-60623-804-2.
- Lilienfeld S. O., Widows M. R. (2005). Psychopathic Personality Inventory—Revised (PPI-R) professional manual. Odessa, FL: Psychological Assessment Resources.
- Antisocial personality disorder – Diagnostic and Statistical Manual of Mental Disorders Fourth edition Text Revision (DSM-IV-TR) American Psychiatric Association (2000) pp. 645–650
- Hare, Robert D. (February 1, 1996). "Psychopathy and Antisocial Personality Disorder: A Case of Diagnostic Confusion". Psychiatric Times 13 (2).
- Hare, Robert D.; Hart, Stephen D.; Harpur, Timothy J. (1991). "Psychopathy and the DSM-IV criteria for antisocial personality disorder". Journal of Abnormal Psychology 100 (3): 391–8. doi:10.1037/0021-843X.100.3.391. PMID 1918618.
- Kupfer, David; Regier, Darrell, eds. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Washington, DC and London, England: American Psychiatric Publishing. ISBN 0890425558.
- Nussbaum, Abraham (2013). The Pocket Guide to the DSM-5 Diagnostic Exam. Arlington, VA: American Psychiatric Publishing. ISBN 978-1-58562-466-9. Retrieved January 5, 2014.
- WHO (2010) ICD-10: Clinical descriptions and diagnostic guidelines: Disorders of adult personality and behavior
- Blair, J; Mitchel D; Blair K (2005). Psychopathy, emotion and the brain. Wiley-Blackwell. pp. 25–7. ISBN 0-631-23336-9.
- Nioche, A.; Pham, T.H.; Ducro, C.; De Beaurepaire, C.; Chudzik, L.; Courtois, R.; Réveillère, C. (2010). "Psychopathie et troubles de la personnalité associés : Recherche d'un effet particulier au trouble borderline ?" [Psychopathy and associated personality disorders: Searching for a particular effect of the borderline personality disorder?]. L'Encéphale (in French) 36 (3): 253–9. doi:10.1016/j.encep.2009.07.004. PMID 20620268.
- Hildebrand, Martin; De Ruiter, Corine (2004). "PCL-R psychopathy and its relation to DSM-IV Axis I and II disorders in a sample of male forensic psychiatric patients in the Netherlands". International Journal of Law and Psychiatry 27 (3): 233–48. doi:10.1016/j.ijlp.2004.03.005. PMID 15177992.
- Nedopil, Norbert; Hollweg, Matthias; Hartmann, Julia; Jaser, Robert (1998). "Comorbidity of Psychopathy with Major Mental Disorders". Psychopathy: Theory, Research and Implications for Society. pp. 257–68. doi:10.1007/978-94-011-3965-6_12. ISBN 978-0-7923-4920-4.
- Smith, Stevens S.; Newman, Joseph P. (1990). "Alcohol and drug abuse-dependence disorders in psychopathic and nonpsychopathic criminal offenders". Journal of Abnormal Psychology 99 (4): 430–9. doi:10.1037/0021-843X.99.4.430. PMID 2266219.
- Kantor, Martin (2006). The Psychopathy of Everyday Life. p. 107. ISBN 0-275-98798-1.
- Skeem, Jennifer; Johansson, Peter; Andershed, Henrik; Kerr, Margaret; Louden, Jennifer Eno (2007). "Two subtypes of psychopathic violent offenders that parallel primary and secondary variants". Journal of Abnormal Psychology 116 (2): 395–409. doi:10.1037/0021-843X.116.2.395. PMID 17516770.
- Wynn, Rolf; Høiseth, Marita H; Pettersen, Gunn (2012-06-01). "Psychopathy in women: theoretical and clinical perspectives". International Journal of Women's Health 4: 257–263. doi:10.2147/IJWH.S25518. ISSN 1179-1411. PMC 3379858. PMID 22723733.
- Eisenbarth, H. (2014-03-01). "[Psychopathic personality in women. Diagnostics and experimental findings in the forensic setting and the business world]". Der Nervenarzt 85 (3): 290, 292–294, 296–297. doi:10.1007/s00115-013-3902-9. ISSN 1433-0407. PMID 24549689.
- Vien, Anh; Beech, Anthony R. (1 July 2006). "Psychopathy: theory, measurement, and treatment". Trauma, Violence & Abuse (Sage Publications) 7 (3): 155–174. doi:10.1177/1524838006288929. ISSN 1524-8380. PMID 16785285. Retrieved 11 April 2016.
- Dingfelder, Sadie F. (March 2004). "Treatment for the 'untreatable'". American Psychological Association. American Psychological Association. Retrieved 12 March 2016.
- Harris, Grant T.; Rice, Marnie E. (2006). "Treatment of Psychopathy: A Review of Empirical Findings". In Patrick, Christopher J. Handbook of psychopathy. New York: Guilford Press. pp. 555–72. ISBN 978-1-59385-591-8.
- Gregory, Sarah; Blair, R James; ffytche, Dominic; Simmons, Andrew; Kumari, Veena; Hodgins, Sheilagh; Blackwood, Nigel (February 2015). "Punishment and psychopathy: a case-control functional MRI investigation of reinforcement learning in violent antisocial personality disordered men". The Lancet Psychiatry 2 (2): 153–160. doi:10.1016/S2215-0366(14)00071-6. Retrieved 12 March 2016.
- "The Hard Sell for Psychopathy Research Funding". Center for Science and Law. Center for Science and Law. Retrieved 10 March 2016.
- Seabrook, John (November 2008). "Suffering Souls: The search for the roots of psychopathy". The New Yorker. Retrieved 10 March 2016.
- Beck, Aaron T., Freeman, Arthur, Davis, Denise D. (2006) Cognitive Therapy of Personality Disorders. Second Edition. The Guilford Press. ISBN 978-1-59385-476-8.
- Chivers, Tom (2014-04-06). "Psychopaths: how can you spot one?". The Telegraph. Retrieved 2015-01-13.
- Bonn, Scott A. (August 2014). "Psychopathic Criminals Cannot Be Cured". Psychology Today. Sussex Publishers, LLC. Retrieved 12 March 2016.
- Mayo Clinic staff (12 April 2013). "Antisocial personality disorder: Treatments and drugs". Mayo Clinic. Mayo Foundation for Medical Education and Research. Retrieved 17 December 2013.
- Brown, Darcy; Larkin, Fintan; Sengupta, amratS; Romero-Ureclay, Jose L.; Ross, Callum C.; Gupta, Nitin; Vinestock, Morris; Das, Mrigendra (October 2014). "Clozapine: an effective treatment for seriously violent and psychopathic men with antisocial personality disorder in a UK high-security hospital.". CNS spectrums 19 (5): 391–402. doi:10.1017/S1092852914000157. PMID 24698103. Retrieved 10 March 2016.
- Khalifa, Najat; Duggan, Conor; Stoffers, Jutta; Huband, Nick; Völlm, Birgit A.; Ferriter, Ferriter; Lieb, Klaus (4 August 2010). "Pharmacological interventions for antisocial personality disorder.". The Cochrane database of systematic reviews (8). doi:10.1002/14651858.CD007667.pub2. PMID 20687091. Retrieved 15 March 2016.
- Mary Ellen O’Toole, Ph.D.; Matt Logan, Ph.D.; and Sharon Smith, Ph.D.. Looking Behind the Mask: Implications for Interviewing Psychopaths in FBI Law Enforcement Bulletin, July 2012, p. 14.
- The Mental Health Act (UK) Reforming The Mental Health Act, Part II, High risk patients Accessed June 26, 2006
- See Section 1 of the act here.
- Paul Harrison; John Geddes (2005-07-18). Lecture Notes: Psychiatry. Blackwell Publishing. pp. 163–165. ISBN 978-1-4051-1869-9.
- "Sexual Predators - Sexual Psychopath Laws". Law Library - American Law and Legal Information. Net Industries. Retrieved 5 April 2016.
- Hacker, Frederick J.; Frym, Marcel (December 1955). "The Sexual Psychopath Act In Practice: A Critical Discussion". California Law Review 43 (5): 766–80. doi:10.15779/Z386J4T. Retrieved 5 April 2016.
- Nathan James, Kenneth R. Thomas, Cassandra Foley. Commitment of Sexually Dangerous Persons. July 2, 2007. Congressional Research Service. http://assets.opencrs.com/rpts/RL34068_20070702.pdf
- Polaschek, Devon L.L.; Daly, Tadhg E. (September 2013). "Treatment and psychopathy in forensic settings". Aggression and Violent Behavior (Elsevier Ltd) 18 (5): 592–603. doi:10.1016/j.avb.2013.06.003. Retrieved 1 April 2016.
- Coid J, Yang M, Ullrich S, Roberts A, Hare RD; Yang; Ullrich; Roberts; Hare (2009). "Prevalence and correlates of psychopathic traits in the household population of Great Britain". International Journal of Law and Psychiatry 32 (2): 65–73. doi:10.1016/j.ijlp.2009.01.002. PMID 19243821.
- Assadi, Seyed Mohammad; Noroozian, Maryam; Pakravannejad, Mahdi; Yahyazadeh, Omid; Aghayan, Shahrokh; Shariat, Seyed Vahid; Fazel, Seena (February 2006). "Psychiatric morbidity among sentenced prisoners: prevalence study in Iran". The British Journal of Psychiatry 188 (2): 159–164. doi:10.1192/bjp.188.2.159. PMID 16449704. Retrieved 1 April 2016.
- Board, Belinda Jane; Fritzon, Katarina (2005). "Disordered personalities at work". Psychology, Crime & Law 11 (1): 17–32. doi:10.1080/10683160310001634304.
- Hare, R. D 1994, ‘Predators: The Disturbing World of the Psychopaths among Us’,Psychology Today, vol. 27, no. 1, pp. 54–61
- Baibak, P; Hare, R. D Snakes in Suits: When Psychopaths Go to Work (2007)
- Boddy, C. R. Corporate Psychopaths: Organizational Destroyers (2011)
- Boddy. C. R (2005) "’The Implications for Business Performance and Corporate Social Responsibility of Corporate Psychopaths" in 2nd International Conference on Business Performance and Corporate Social Responsibility, ed. M. Hopkins, Middlesex University Business School, London
- Walker, I. 2005, Psychopaths in Suits, Australian Broadcasting Corporation
- Babiak, Paul; Neumann, Craig S.; Hare, Robert D. (April 2010). "Corporate psychopathy: Talking the walk.". Behavioral Sciences & the Law 28 (2): 174–93. doi:10.1002/bsl.925. PMID 20422644.
- James O Office Politics: How to Thrive in a World of Lying, Backstabbing and Dirty Tricks (2013)
- Hare R D Without Conscience: The Disturbing World of the Psychopaths Among Us 1993
- Be cautious - socially adapted psychopath, damned attractive man
- sociopaths and narcissists in movies
- Neumann, Craig S. "Will the Real Psychopath Please Stand Up?". research.unt.edu. University of North Texas. Retrieved 23 April 2016.
- "Psychopathy", Online Etymology Dictionary Retrieved August 1st 2011
- Online Etymology Dictionary: Psychopathic Retrieved January 21st 2012
- Online Etymology Dictionary: Psychopath Retrieved January 21st 2012
- Online Etymology Dictionary: Pathological Retrieved January 21st 2012
- Medlineplus Psychopath or Psychopathy Retrieved January 21st 2012
- Medilexicon powered by Stedman's, part of Lippincott Williams & Wilkins Psychopath Retrieved January 21st 2012
- Burgy, M. (2008). "The Concept of Psychosis: Historical and Phenomenological Aspects". Schizophrenia Bulletin 34 (6): 1200–10. doi:10.1093/schbul/sbm136. PMC 2632489. PMID 18174608.
- Online Etymology Dictionary: Psychopathic
- "Psycho". Dictionary.com. Retrieved 7 Sep 2013.
- Lykken, David T. (1995). The Antisocial Personalities. ISBN 978-0-8058-1941-0.[page needed]
- Rutter, Steve (2007). The Psychopath: Theory, Research, and Practice. New Jersey: Lawrence Erlbaum Associates. p. 37. ISBN 0-8058-6079-7.
- Online Etymology Dictionary: Socio-
- Current Conceptions of Psychopathic Personality G. E. Partridge, The American Journal of Psychiatry. 1930 July ; 1(87):53–99
- International Handbook on Psychopathic Disorders and the Law, Volume 1, Alan Felthous, Henning Sass, 15 Apr 2008
- Psychopathy in the Treatment of Forensic Psychiatric Patients: Assessment, Prevalence, Predictive Validity, and Clinical Implications Martin Hildebrand, Rozenberg Publishers, 16 Jun 2005
- Epitome of Current Literature: Current Conceptions of Psychopathic Disorder by Partridge, G.E., M. Hamblin Smith, The British Journal of Psychiatry (1930) 76: 838
- Hare, Robert (2006). Snakes in Suits: When Psychopaths Go To Work. New York, NY: HarperCollins Publishers. ISBN 0-06-083772-1.
- Skilling, TA; GT Harris; ME Rice; VL Quinsey (March 2002). "Identifying persistently antisocial offenders using the Hare Psychopathy Checklist and DSM antisocial personality disorder criteria". American Psychological Assosiation.
- Berrios, G.E. (1999). "Classic Text No. 37: J. C. Prichard and the concept of 'moral insanity'". History of Psychiatry 10 (37): 111–26. doi:10.1177/0957154X9901003706. PMID 11623816.
- Berrios, G.E. (1993). "European views on personality disorders: A conceptual history". Comprehensive Psychiatry 34 (1): 14–30. doi:10.1016/0010-440X(93)90031-X. PMID 8425387.
- Langer, Walter C. (1972) . The Mind of Adolf Hitler: The Secret Wartime Report. New York: Basic Books. p. 126. ISBN 978-0-465-04620-1.
- Bluglass, R (1994). "Who's psychopathic now? A recent report has few new solutions and calls for more research". BMJ 309 (6958): 826. doi:10.1136/bmj.309.6958.826. PMC 2541046. PMID 7950601.
- Craig, Leam; Browne, Kevin; Beech, Anthony R. (2008). Assessing Risk in Sex Offenders. John Wiley and Sons. p. 117. ISBN 0-470-01898-4.
- The Shadow Warriors: OSS and the Origins of the CIA Bradley F Smith. Times Books. 1983
- Klara Hitler's Son: Reading the Langer Report on Hitler's Mind Spark, Clare L. Social Thought and Research, Volume 22, Number 1&2 (1999), pp. 113-137
- Walters, Glenn D. (2006). "Hitler the Psychopath". Lifestyle Theory: Past, Present, and Future. Nova Publishers. pp. 42–3. ISBN 978-1-60021-033-4.
- Paul Babiak & Robert D. Hare. Snakes in Suits: When Psychopaths Go to Work. HarperCollins, New York, NY. ISBN 978-0-06-114789-0
- Black, Will (2014) Psychopathic Cultures and Toxic Empires Frontline Noir, Edinburgh ISBN 978-1904684718
- Blair, J. et al. (2005) The Psychopath – Emotion and the Brain. Malden, MA: Blackwell Publishing, ISBN 978-0-631-23335-0
- Cleckley, Hervey M. The Mask of Sanity: An Attempt to Reinterpret the So-Called Psychopathic Personality, 5th Edition, revised 1984, PDF file download.
- Dutton, K. (2012) The Wisdom of Psychopaths ISBN 978-0-374-70910-5 (e-book)
- Hare, Robert D. (1999). Without Conscience: The Disturbing World of the Psychopaths Among Us. New York: Guilford Press. ISBN 1-57230-451-0.
- Häkkänen-Nyholm, H. & Nyholm, J-O. (2012). Psychopathy and Law: A Practitioners Guide. Chichester: John Wiley & Sons.
- Kiehl, Kent (2014). The psychopath whisperer : the science of those without a conscience. New York: Crown Publishers. ISBN 978-0-7704-3584-4.
- Oakley, Barbara, Ph.D., Evil Genes: Why Rome Fell, Hitler Rose, Enron Failed, and My Sister Stole My Mother's Boyfriend. Prometheus Books, Amherst, NY, 2007, ISBN 1-59102-665-2.
- Thiessen, W Slip-ups and the dangerous mind: Seeing through and living beyond the psychopath (2012)
- Michael H. Thimble, F.R.C.P., F.R.C. Psych. Psychopathology of Frontal Lobe Syndromes.
- Widiger, Thomas (1995). Personality Disorder Interview-IV, Chapter 4: Antisocial Personality Disorder. Psychological Assessment Resources, Inc. ISBN 0-911907-21-1.
|Look up psychopathy in Wiktionary, the free dictionary.|
- Dangerous Psychopaths: Criminally Responsible But Not Morally Responsible San Diego Law Review (2011)
- Psychopath: A Documentary Film
- Handbook of Psychopathy (2007) on Google Books.
- The Mask of Sanity, 5th Edition, PDF of Cleckley's book, 1988
- Without Conscience Official web site of Dr. Robert Hare
- Philpapers Psychopathy
- Understanding The Psychopath: Key Definitions & Research
- The Paradox of Psychopathy Psychiatric Times, 2007 (nb: inconsistent access)
- Into the Mind of a Killer Nature, 2001
- Can A Test Really Tell Who's A Psychopath? NPR audio, text and expert panel report, 2011
- What Psychopaths Teach Us about How to Succeed Scientific American, October 2012