Neuroticism is a fundamental personality trait in the study of psychology characterized by anxiety, moodiness, worry, envy, and jealousy. Individuals who score high on neuroticism are more likely than the average to experience such feelings as anxiety, anger, envy, guilt, and depressed mood. They respond more poorly to stressors, are more likely to interpret ordinary situations as threatening, and minor frustrations as hopelessly difficult. They are often self-conscious and shy, and they may have trouble controlling urges and delaying gratification. Neuroticism is a risk factor for the "internalizing" mental disorders such as phobia, depression, panic disorder, and other anxiety disorders, all of which are traditionally called neuroses.
At the opposite end of the spectrum, individuals who score low in neuroticism are more emotionally stable and less reactive to stress. They tend to be calm, even-tempered, and less likely to feel tense or rattled. Although they are low in negative emotion, they are not necessarily high on positive emotion. Being high on positive emotion is an element of the independent trait of extraversion. Neurotic extraverts, for example, would experience high levels of both positive and negative emotional states, a kind of "emotional roller coaster". Individuals who score low on neuroticism (particularly those who are also high on extraversion) generally report more happiness and satisfaction with their lives.
Like other personality traits, neuroticism is typically viewed as a continuous dimension rather than distinct. Neuroticism test scores approximate a normal distribution given a large enough sample of people.
Extent of neuroticism is generally assessed using self-report measures, although peer-reports and third-party observation can also be used. Self-report measures are either lexical or based on statements. Deciding which measure of either type to use in research is determined by an assessment of psychometric properties and the time and space constraints of the study being undertaken.
Lexical measures use individual adjectives that reflect neurotic traits, such as anxiety, envy, jealously, moodiness, and are very space and time efficient for research purposes. Goldberg (1992) developed a 20-word measure as part of his 100-word Big Five markers. Saucier (1994) developed a briefer 8-word measure as part of his 40-word mini-markers. Thompson (2008)  systematically revised these measures to develop the International English Mini-Markers which has superior validity and reliability in populations both within and outside North America. Internal consistency reliability of the International English Mini-Markers for the Neuroticism (emotional stability) measure for native English-speakers is reported as .84, that for non-native English-speakers is .77.
Statement measures tend to comprise more words, and hence consume more research instrument space, than lexical measures. Respondents are asked the extent to which they, for example, Remain calm under pressure, or Have frequent mood swings. While some statement-based measures of neuroticism have similarly acceptable psychometric properties in North American populations to lexical measures, their generally emic development makes them less suited to use in other populations. For instance, statements in colloquial North American English like Seldom feel blue and Am often down in the dumps are sometimes hard for non-native English-speakers to understand.
Neuroticism has also been studied from the perspective of Gray's biopsychological theory of personality, using a scale that measures personality along two dimensions: the Behavioural Inhibition System (BIS) and the Behavioural Activation System (BAS). The BIS is thought to be related to sensitivity to punishment as well as avoidance motivation, while the BAS is thought to be related to sensitivity to reward as well as approach motivation. Neuroticism has been found to be positively correlated with the BIS scale, and negatively correlated with the BAS scale.
Research has found that a wide range of clinical mental disorders are associated with elevated levels of neuroticism compared to levels in the general population. Disorders associated with elevated neuroticism include mood disorders, such as depression and bipolar disorder, anxiety disorders, eating disorders, schizophrenia and schizoaffective disorder, dissociative identity disorder, and hypochondriasis. Mood disorders tend to have a much larger association with neuroticism than these other disorders. Personality disorders as listed in DSM-IV in general tend to be associated with elevated neuroticism. A meta-analysis found that Borderline, Paranoid, Schizotypal, Avoidant, and Dependent Personality disorders were each associated with substantial levels of neuroticism (correlations ranging from .28 to .49). The remaining personality disorders had either modest positive or non-significant (in the case of narcissistic and histrionic) associations with neuroticism.
Neuroticism appears to be related to physiological differences in the brain. Hans Eysenck theorized that neuroticism is a function of activity in the limbic system, and his research suggests that people who score highly on measures of neuroticism have a more reactive sympathetic nervous system, and are more sensitive to environmental stimulation. Behavioral genetics researchers have found that a significant portion of the variability on measures of neuroticism can be attributed to genetic factors.
A study with positron emission tomography has found that healthy subjects that score high on the NEO PI-R neuroticism dimension tend to have high altanserin binding in the frontolimbic region of the brain — an indication that these subjects tend to have more of the 5-HT2A receptor in that location. Another study has found that healthy subjects with a high neuroticism score tend to have higher DASB binding in the thalamus; DASB is a ligand that binds to the serotonin transporter protein.
Another neuroimaging study using magnetic resonance imaging to measure brain volume found that the brain volume was negatively correlated to NEO PI-R neuroticism when correcting for possible effects of intracranial volume, sex, and age.
Other studies have associated neuroticism with genetic variations, e.g., with 5-HTTLPR — a polymorphism in the serotonin transporter gene. However, not all studies find such an association. A genome-wide association study (GWA study) has associated single-nucleotide polymorphisms in the MDGA2 gene with neuroticism, however the effect sizes were small. Another GWA study gave some evidence that the rs362584 polymorphism in the SNAP25 gene was associated with neuroticism.
A 2008 experiment investigated the neurophysiological responses to uncertainty (which individuals high in neuroticism find aversive) using an event-related potential framework. Participants received positive, negative and uncertain feedback on a task while the feedback-related negativity (FRN), an evoked potential that peaks approximately 250 ms after the receipt of feedback information, was measured. For all participants, it was found that a larger FRN occurred after negative feedback than after positive feedback. However, for participants high on neuroticism, uncertain feedback resulted in a larger neural response than did negative feedback.
A 2009 study has found that higher neuroticism is associated with greater loss of brain volume with increasing age.
Studies have found that the mean reaction times will not differ between individuals high in neuroticism and those low in neuroticism, but that there is considerably more trial-to-trial variability in performance reflected in reaction time standard deviations. In other words, on some trials neurotic individuals are faster than average, and on others they are slower than average. It has been suggested that this variability reflects noise in the individual's information processing systems or instability of basic cognitive operations (such as regulation processes), and further that this noise originates from two sources: mental preoccupations and reactivity processes.
Flehmig et al. (2007) studied mental noise in terms of everyday behaviours using the Cognitive Failures Questionnaire, which is a self-report measure of the frequency of slips and lapses of attention. A 'slip' is an error by commission, and a 'lapse' is an error by omission. This scale was correlated with two well-known measures of neuroticism, the BIS/BAS scale and the Eysenck Personality Questionnaire. Results indicated that the CFQ-UA (Cognitive Failures Questionnaire- Unintended Activation) subscale was most strongly correlated with neuroticism (r = .40)[clarification needed] and explained the most variance (16%) compared to overall CFQ scores which only explained 7%. The authors interpret these findings as suggesting that mental noise is "highly specific in nature" as it is related most strongly to attention slips triggered endogenously by associative memory. In other words, this may suggest that mental noise is mostly task-irrelevant cognitions such as worries and preoccupations.
The results of one study has found that, on average, women score moderately higher than men on neuroticism. This study examined sex differences in the 'Big Five' personality traits across 55 nations. It found that across the 55 nations studied, the most pronounced difference was in neuroticism. This study found that: In 49 of the 55 nations studied, women scored higher in neuroticism than men. In no country did men report significantly higher neuroticism than women. In Botswana and Indonesia, men scored slightly higher than women. Sex differences in neuroticism within nations ranged from very small to quite large - large in 17 and moderate in 29. Differences were negligible in Bangladesh, Tanzania, Ethiopia, Greece, Japan, Botswana and Indonesia. Large differences were recorded in Israel and Morocco. African and Asian/South Asian world regions tended to have smaller sex differences in personality overall than did western world regions (Europe, and North and South America). Women tended to record similar levels of neuroticism across the regions covered in the study. The men's scores differed widely; men in the Western regions scored lower on neuroticism compared to men in African and Asian world regions. In countries with higher levels of human development, the men recorded significantly lower levels of neuroticism.
||The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. (September 2012)|
Neuroticism, along with other personality traits, has been mapped across states in the USA. People in eastern states such as New York, New Jersey, West Virginia, and Mississippi tend to score high on neuroticism, whereas people in many western states, such as Utah, Colorado, South Dakota, Oregon, and Arizona score lower on average. People in states that are higher in neuroticism also tend to have higher rates of heart disease and lower life expectancy.
One of the theories regarding evolutionary approaches to depression focuses on neuroticism. A moderate amount of neuroticism may provide benefits, such as increased drive and productivity, due to greater sensitivity to negative outcomes. Too much, however, may reduce fitness by producing, for example, recurring depressions. Thus, evolution will select for an optimal amount and most people will have neuroticism near this optimum. However, because neuroticism likely has a normal distribution in the population, a minority will be highly neurotic.
Neuroticism has been included as one of the four dimensions that comprise core self-evaluations, one's fundamental appraisal of oneself, along with locus of control, self-efficacy, and self-esteem. The concept of core self-evaluations was first examined by Judge, Locke, and Durham (1997), and since found evidence to suggest these have the ability to predict several work outcomes, specifically, job satisfaction and job performance.
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