Obsessive-compulsive and related disorders are defined by repetitive thoughts and behaviours that are so extreme that they interfere with everyday life. Obsessions are repetitive thoughts and urges. Compulsions are repetitive behaviours or mental acts. Compulsions are often not seen as pleasurable by the patient. OCD begins before age 10 or in late adolescence/early adulthood.

Clinical profile Obsessive-compulsive disorder:

People with body dysmorphic disorder (BDD) are preoccupied with one or more imagined or exaggerated defects in their appearance. People with BDD find it very hard to stop thinking about their concerns. BDD is associated with suicide ideation. It typically begins in adolescence. If weight and body shape are the only concerns about appearance, it might fit the profile of an eating disorder better. Clinical profile body dysmorphic disorder:

People with a hoarding disorder are extremely attached to their possessions and are very resistant to efforts to get rid of them. Hoarders are often unaware of the severity of their behaviour. Hoarding behaviour usually begins in childhood or early adolescence. Animal hoarding often does not emerge until middle age or older.

Clinical profile hoarding disorder:

The lifetime prevalence of OCD and BDD is 2%. The lifetime prevalence of hoarding disorder is 1.5%. OCD and BDD are slightly more common among women than men. There is high comorbidity with the disorders and all disorders are associated with depression and anxiety disorders.

Heritability in OCD, BDD and hoarding disorders is between 40% and 50%. The orbitofrontal cortex, the caudate nucleus and the anterior cingulate are unusually active in people with OCD.

Conditioned responses are slower to go extinct in people with OCD. According to the cognitive behavioural model of obsessions and compulsions, OCD is related to a deficit in the intuitive sense of feeling security and closure. Yedasentience is a subjective feeling of knowing that you have thought enough, cleaned enough, or in other ways done what you should prevent chaos and danger from low-level threats in the environment. People with OCD may have a deficit in yedasentience.

It is also possible that people with OCD try harder to suppress their obsessions than other people and in doing so make the situation worse. The white bear effect refers to thinking about something that you try to suppress.

People with BDD may examine one feature at a time instead of seeing physical features as a whole, making it more likely that they will become engrossed in considering a small flaw. They also find attractiveness more important than most people.

Motivational strategies may be used in hoarding disorders as insight is necessary for therapy to address the hoarding symptoms. Getting rid of items quickly in hoarders is not effective.

Post-traumatic stress disorder (PTSD) entails an extreme response to a severe stressor. Diagnosis of PTSD includes intrusive thoughts, avoidance, negative mood and thoughts and increased arousal and reactivity. Trauma is an event that involved actual or threatened death, serious injury or sexual violation.

Clinical profile PTSD:

Acute stress disorder is similar to PTSD, but the duration is shorted. The diagnosis is only applicable when the symptoms last for 3 days to one month. ASD could stigmatize normal short-term reactions to trauma. PTSD is highly comorbid with other disorders such as anxiety disorders or depressive disorders. Women are twice as likely to develop PTSD as are men.

PTSD is related to genetic risk for anxiety disorders. High activity in the amygdala, childhood exposure to trauma and tendencies to attend selectively to cues of threat are risk factors of developing PTSD. Neuroticism and negative affectivity also predict the onset of PTSD. The people that were exposed to the most severe traumas are most likely to develop PTSD. Traumas caused by humans are more likely to cause PTSD than natural disasters. A smaller than average hippocampus is associated with developing PTSD and the likelihood of developing PTSD. A person with PTSD may sustain strong memories for sensory aspects of the trauma but find it difficult to recall because of the smaller hippocampus. People who have symptoms of dissociation during and immediately after the trauma re more likely to develop PTSD. High intelligence and strong social support may help a person cope with severe traumas more adaptively.

Antidepressants can help in the treatment of PTSD. Exposure treatment is usually used for treating PTSD, but the symptoms can become worse before they improve. Early exposure treatment seems especially effective. EMDR is also used to treat PTSD.