Intrusive thoughts are unwelcome involuntary thoughts, images, or unpleasant ideas that may become obsessions, are upsetting or distressing, and can be difficult to manage or eliminate. When they are associated with obsessive-compulsive disorder (OCD), depression, body dysmorphic disorder (BDD), and sometimes attention-deficit hyperactivity disorder (ADHD), the thoughts may become paralyzing, anxiety-provoking, or persistent. Intrusive thoughts may also be associated with episodic memory, unwanted worries or memories from OCD, posttraumatic stress disorder, other anxiety disorders, eating disorders, or psychosis. Intrusive thoughts, urges, and images are of inappropriate things at inappropriate times, and they can be divided into three categories: "inappropriate aggressive thoughts, inappropriate sexual thoughts, or blasphemous religious thoughts".
Many people experience the type of bad or unwanted thoughts that people with more troubling intrusive thoughts have, but most people are able to dismiss these thoughts. For most people, intrusive thoughts are a "fleeting annoyance." London psychologist Stanley Rachman presented a questionnaire to healthy college students and found that virtually all said they had these thoughts from time to time, including thoughts of sexual violence, sexual punishment, "unnatural" sex acts, painful sexual practices, blasphemous or obscene images, thoughts of harming elderly people or someone close to them, violence against animals or towards children, and impulsive or abusive outbursts or utterances. Such bad thoughts are universal among humans, and have "almost certainly always been a part of the human condition".
When intrusive thoughts occur with obsessive-compulsive disorder (OCD), patients are less able to ignore the unpleasant thoughts and may pay undue attention to them, causing the thoughts to become more frequent and distressing. The thoughts may become obsessions which are paralyzing, severe, and constantly present, and can range from thoughts of violence or sex to religious blasphemy. Distinguishing them from normal intrusive thoughts experienced by many people, the intrusive thoughts associated with OCD may be anxiety provoking, irrepressible, and persistent.
How people react to intrusive thoughts may determine whether these thoughts will become severe, turn into obsessions, or require treatment. Intrusive thoughts can occur with or without compulsions. Carrying out the compulsion reduces the anxiety, but makes the urge to perform the compulsion stronger each time it recurs, reinforcing the intrusive thoughts. According to Baer, suppressing the thoughts only makes them stronger, and recognizing that bad thoughts do not signify that one is truly evil is one of the steps to overcoming them. There is evidence of the benefit of acceptance as an alternative to suppression of intrusive thoughts. A study showed that those instructed to suppress intrusive thoughts experienced more distress after suppression, while patients instructed to accept the bad thoughts experienced decreased discomfort. These results may be related to underlying cognitive processes involved in OCD. But, accepting the thoughts can be more difficult for persons with OCD. In the 19th century, OCD was known as "the doubting sickness"; the "pathological doubt" that accompanies OCD can make it harder for a person with OCD to distinguish "normal" intrusive thoughts as experienced by most people, causing them to "suffer in silence, feeling too embarrassed or worried that they will be thought crazy".
The possibility that most patients suffering from intrusive thoughts will ever act on those thoughts is low. Patients who are experiencing intense guilt, anxiety, shame, and upset over these thoughts are different from those who actually act on them. The history of violent crime is dominated by those who feel no guilt or remorse; the very fact that someone is tormented by intrusive thoughts and has never acted on them before is an excellent predictor that they will not act upon the thoughts. Patients who are not troubled or shamed by their thoughts, do not find them distasteful, or who have actually taken action, might need to have more serious conditions such as psychosis or potentially criminal behaviors ruled out. According to Baer, a patient should be concerned that intrusive thoughts are dangerous if the person does not feel upset by the thoughts, or rather finds them pleasurable; has ever acted on violent or sexual thoughts or urges; hears voices or sees things that others do not see; or feels uncontrollable irresistible anger.
Inappropriate aggressive thoughts
Intrusive thoughts may involve violent obsessions about hurting others or themselves. They can include such thoughts as harming an innocent child, jumping from a bridge, mountain or the top of a tall building, urges to jump in front of a train or automobile, and urges to push another in front of a train or automobile. Rachman's survey of healthy college students found that virtually all of them had intrusive thoughts from time to time, including:
- Causing harm to elderly people
- Imagining or wishing harm upon someone close to oneself
- Impulses to violently attack, hit, harm or kill a person, small child, or animal
- Impulses to shout at or abuse someone, or attack and violently punish someone, or say something rude, inappropriate, nasty or violent to someone.
These thoughts are part of being human, and need not ruin the quality of life. Treatment is available when the thoughts are associated with OCD and become persistent, severe, or distressing.
Inappropriate sexual thoughts
Sexual obsessions involve intrusive thoughts or images of "kissing, touching, fondling, oral sex, anal sex, intercourse, and rape" with "strangers, acquaintances, parents, children, family members, friends, coworkers, animals and religious figures", involving "heterosexual or homosexual content" with persons of any age.
Like other unwanted intrusive thoughts or images, everyone has some inappropriate sexual thoughts at times, but people with OCD may attach significance to the unwanted sexual thoughts, generating anxiety and distress. The doubt that accompanies OCD leads to uncertainty regarding whether one might act on the intrusive thoughts, resulting in self-criticism or loathing.
One of the more common sexual intrusive thoughts occurs when an obsessive person doubts his or her sexual identity. As in the case of most sexual obsessions, sufferers may feel shame and live in isolation, finding it hard to discuss their fears, doubts, and concerns about their sexual identity.
A person experiencing sexual intrusive thoughts may feel shame, "embarrassment, guilt, distress, torment, fear that you may act on the thought or perceived impulse, and doubt about whether you have already acted in such a way." Depression may be a result of the self-loathing that can occur, depending on how much the OCD interferes with daily functioning or causes distress. Their concern over these thoughts may cause them to scrutinize their bodies to determine if the thoughts result in feelings of arousal. But, focusing attention of any part of the body can result in feelings in that part of the body, hence doing so may decrease confidence and increase fear about acting on the urges. Part of treatment of sexual intrusive thoughts involves therapy to help sufferers accept intrusive thoughts and stop trying to reassure themselves by checking their bodies.
Blasphemous religious thoughts
Blasphemous thoughts are a common component of OCD, documented throughout history; notable religious figures such as Martin Luther and St. Ignatius were known to be tormented by intrusive, blasphemous or religious thoughts and urges. Martin Luther had urges to curse God and Jesus, and was obsessed with images of "the Devil's behind". St. Ignatius had numerous obsessions, including the fear of stepping on pieces of straw forming a cross, fearing that it showed disrespect to Christ. A study of 50 patients with a primary diagnosis of obsessive-compulsive disorder found that 40% had religious and blasphemous thoughts and doubts—a higher, but not statistically significantly different number than the 38% who had the obsessional thoughts related to dirt and contamination more commonly associated with OCD. One study suggests that content of intrusive thoughts may vary depending on culture, and that blasphemous thoughts may be more common in men than in women.
According to Fred Penzel, a New York psychologist, some common religious obsessions and intrusive thoughts are:
- sexual thoughts about God, saints, and religious figures
- bad thoughts or images during prayer or meditation
- thoughts of being possessed
- fears of sinning or breaking a religious law or performing a ritual incorrectly
- fears of omitting prayers or reciting them incorrectly
- repetitive and intrusive blasphemous thoughts
- urges or impulses to say blasphemous words or commit blasphemous acts during religious services.
Suffering can be greater and treatment complicated when intrusive thoughts involve religious implications; patients may believe the thoughts are inspired by Satan, and may fear punishment from God or have magnified shame because they perceive themselves as sinful. Symptoms can be more distressful for sufferers with strong religious convictions or beliefs.
Baer believes that blasphemous thoughts are more common in Catholics and evangelical Protestants than in other religions, whereas Jews or Muslims tend to have obsessions related more to complying with the laws and rituals of their faith, and performing the rituals perfectly. He hypothesizes that this is because what is considered inappropriate varies among cultures and religions, and intrusive thoughts torment their sufferers with whatever is considered most inappropriate in the surrounding culture.
Intrusive thoughts are associated with OCD or obsessive-compulsive personality disorder, but may also occur with other conditions such as post-traumatic stress disorder, clinical depression, postpartum depression, and anxiety. One of these conditions is almost always present in people whose intrusive thoughts reach a clinical level of severity. A large study published in 2005 found that aggressive, sexual, and religious obsessions were broadly associated with comorbid anxiety disorders and depression. The intrusive thoughts that occur in a schizophrenic episode differ from the obsessional thoughts that occur with OCD or depression in that the intrusive thoughts of schizophrenics are false or delusional beliefs (i.e. held by the schizophrenic individual to be real and not doubted, as is typically the case with intrusive thoughts) .
Post-traumatic stress disorder
The key difference between OCD and post-traumatic stress disorder (PTSD) is that the intrusive thoughts of PTSD sufferers are of traumatic events that actually happened to them, whereas OCD sufferers have thoughts of imagined catastrophes. PTSD patients with intrusive thoughts have to sort out violent, sexual, or blasphemous thoughts from memories of traumatic experiences. When patients with intrusive thoughts do not respond to treatment, physicians may suspect past physical, emotional, or sexual abuse.
People who are clinically depressed may experience intrusive thoughts more intensely, and view them as evidence that they are worthless or sinful people. The suicidal thoughts that are common in depression must be distinguished from intrusive thoughts, because suicidal thoughts—unlike harmless sexual, aggressive, or religious thoughts—can be dangerous.
Unwanted thoughts by mothers about harming their newborn infants are common in postpartum depression. A 1999 study of 65 women with postpartum major depression by Katherine Wisner et al. found the most frequent aggressive thought for women with postpartum depression was causing harm to their newborn infants. A study of 85 new parents found that 89% experienced intrusive images, for example, of the baby suffocating, having an accident, being harmed, or being kidnapped.
Some women may develop symptoms of OCD during pregnancy or the postpartum period. Postpartum OCD occurs mainly in women who may already have OCD, perhaps in a mild or undiagnosed form. Postpartum depression and OCD may be comorbid (often occurring together). And though physicians may focus more on the depressive symptoms, one study found that obsessive thoughts did accompany postpartum depression in 57% of new mothers.
Wisner found common obsessions about harming babies in mothers experiencing postpartum depression include images of the baby lying dead in a casket or being eaten by sharks; stabbing the baby; throwing the baby down the stairs; or drowning or burning the baby (as by submerging it in the bathtub in the former case or throwing it in the fire or putting it in the microwave in the latter).  Baer estimates that up to 200,000 new mothers with postpartum depression each year may develop these obsessional thoughts about their babies; and because they may be reluctant to share these thoughts with a physician or family member, or suffer in silence and fear they are "crazy", their depression can worsen.
Intrusive fears of harming immediate children can last longer than the postpartum period. A study of 100 clinically depressed women found that 41% had obsessive fears that they might harm their child, and some were afraid to care for their children. Among non-depressed mothers, the study found 7% had thoughts of harming their child—a rate that yields an additional 280,000 non-depressed mothers in the United States with intrusive thoughts about harming their children.
In the field of analytical psychology intrusive thoughts can be understood as unconscious parts of one's personality that affect them directly (due to the contents of the intrusive thoughts being associated with unconscious complexes). The self-sabotaging nature of intrusive thoughts is also seen in a more teleological approach, as a way for the shadow to reach consciousness and be dealt with and integrated by the ego.
According to Baer, most people who suffer bad or unacceptable thoughts have not identified themselves as having OCD, because they may not have what they believe to be classic symptoms of OCD, such as handwashing. Yet, he says, epidemiological studies suggest that intrusive thoughts are the most common kind of OCD worldwide; if people in the United States with intrusive thoughts gathered, they would form the fourth-largest city in the US, following New York City and Chicago. A 2007 study found that 78% of a clinical sample of OCD patients had intrusive images.
The prevalence of OCD in every culture studied is at least 2% of the population, and the majority of those have obsessions, or bad thoughts, only; this results in a conservative estimate of more than 2 million sufferers in the United States alone (as of 2000). One author estimates that one in 50 adults has OCD and about 10–20% of these have sexual obsessions. A recent study found that 25% of 293 patients with a primary diagnosis of OCD had a history of sexual obsessions.
Treatment for intrusive thoughts is similar to treatment for OCD. Exposure and response prevention therapy—also referred to as habituation or desensitization—is useful in treating intrusive thoughts. Mild cases can also be treated with cognitive behavioral therapy, which helps patients identify and manage the unwanted thoughts.
Exposure therapy is the treatment of choice for intrusive thoughts. According to Deborah Osgood-Hynes, Psy.D. Director of Psychological Services and Training at the MGH/McLean OCD Institute, "In order to reduce a fear, you have to face a fear. This is true of all types of anxiety and fear reactions, not just OCD."
Because it is uncomfortable to experience bad thoughts and urges, shame, doubt or fear, the initial reaction is usually to do something to make the feelings diminish. By engaging in a ritual or compulsion to diminish the anxiety or bad feeling, the action is strengthened via a process called negative reinforcement—the mind learns that the way to avoid the bad feeling is by engaging in a ritual or compulsions. When OCD becomes severe, this leads to more interference in life and continues the frequency and severity of the thoughts the person sought to avoid.
Exposure therapy (or exposure and response prevention) is the practice of staying in an anxiety-provoking or feared situation until the distress or anxiety diminishes. The goal is to reduce the fear reaction, learning to not react to the bad thoughts. This is the most effective way to reduce the frequency and severity of the intrusive thoughts. The goal is to be able to "expose yourself to the thing that most triggers your fear or discomfort for one to two hours at a time, without leaving the situation, or doing anything else to distract or comfort you." Exposure therapy will not completely eliminate intrusive thoughts—everyone has bad thoughts—but most patients find that it can decrease their thoughts sufficiently that intrusive thoughts no longer interfere with their lives.
Cognitive behavioral therapy
Cognitive behavioral therapy (CBT) is a newer therapy than exposure therapy, available for those unable or unwilling to undergo exposure therapy. Cognitive therapy has been shown to be useful in reducing intrusive thoughts, but developing a conceptualization of the obsessions and compulsions with the patient is important.
Antidepressants or antipsychotic medications may be used for more severe cases if intrusive thoughts do not respond to cognitive behavioral or exposure therapy alone. Whether the cause of intrusive thoughts is OCD, depression, or post-traumatic stress disorder, the selective serotonin reuptake inhibitor (SSRI) drugs (a class of antidepressants) are the most commonly prescribed. Intrusive thoughts may occur in persons with Tourette syndrome (TS) who also have OCD; the obsessions in TS-related OCD are thought to respond to SSRI drugs as well.
Antidepressants which have been shown to be effective in treating OCD include fluvoxamine (trade name Luvox), fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), and clomipramine (Anafranil). Although SSRIs are known to be effective for OCD in general, there have been fewer studies on their effectiveness for intrusive thoughts. A retrospective chart review of patients with sexual symptoms treated with SSRIs showed the greatest improvement was in those with intrusive sexual obsessions typical of OCD. A study of ten patients with religious or blasphemous obsessions found that most patients responded to treatment with fluoxetine or clomipramine. Women with postpartum depression often have anxiety as well, and may need lower starting doses of SSRIs; they may not respond fully to the medication, and may benefit from adding cognitive behavioral or response prevention therapy.
Patients with intense intrusive thoughts that do not respond to SSRIs or other antidepressants may be prescribed typical and atypical neuroleptics including risperidone (trade name Risperdal), ziprasidone (Geodon), haloperidol (Haldol), and pimozide (Orap).
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