However, drug addiction among people with OCD may be a compulsive behavior. Depression is also extremely prevalent among people with OCD. One explanation for the high depression rate among OCD populations was posited by Mineka, Watson, and Clark (1998), who explained that people with OCD, or any other anxiety disorder, may feel "out of control".Someone exhibiting OCD signs does not necessarily have OCD. Behaviors that present as obsessive–compulsive can also be found in a number of other conditions, including obsessive–compulsive personality disorder (OCPD), autism spectrum disorder (ASD), or disorders in which perseveration is a possible feature (ADHD, PTSD, bodily disorders, or stereotyped behaviors). Some cases of OCD present symptoms typically associated with Tourette syndrome, such as compulsions that may appear to resemble motor tics; this has been termed tic-related OCD or Tourettic OCD.OCD frequently occurs comorbidly with both bipolar disorder and major depressive disorder. Between 60 and 80% of those with OCD experience a major depressive episode in their lifetime. Comorbidity rates have been reported at between 19 and 90%, as a result of methodological differences. Between 9–35% of those with bipolar disorder also have OCD, compared to 1–2% in the general population. About 50% of those with OCD experience cyclothymic traits or hypomanic episodes. OCD is also associated with anxiety disorders. Lifetime comorbidity for OCD has been reported at 22% for specific phobia, 18% for social anxiety disorder, 12% for panic disorder, and 30% for generalized anxiety disorder. The comorbidity rate for OCD and ADHD has been reported to be as high as 51%.
Causes
The cause of OCD is unknown. Both environmental and genetic factors are believed to play a role. Risk factors include a history of child abuse or other stress-inducing events. Drug-induced OCD
Some medications and other drugs, such as methamphetamine or cocaine, can induce obsessive-compulsive disorder (OCD) in people without previous symptoms.Some atypical antipsychotics (second-generation antipsychotics) such as olanzapine (Zyprexa) and clozapine (Clozaril) can induce OCD in people, particularly individuals with schizophrenia. Genetics
There appear to be some genetic components of OCD causation, with identical twins more often affected than fraternal twins. Furthermore, individuals with OCD are more likely to have first-degree family members exhibiting the same disorders than matched controls. In cases in which OCD develops during childhood, there is a much stronger familial link in the disorder than with cases in which OCD develops later in adulthood. In general, genetic factors account for 45–65% of the variability in OCD symptoms in children diagnosed with the disorder. A 2007 study found evidence supporting the possibility of a heritable risk for OCD.Research has found there to be a genetic correlation between anorexia nervosa and OCD, suggesting a strong etiology. First and second hand relatives of probands with OCD have a greater risk of developing anorexia nervosa as genetic relatedness increases.A mutation has been found in the human serotonin transporter gene hSERT in unrelated families with OCD.A systematic review found that while neither allele was associated with OCD overall, in Caucasians, the L allele was associated with OCD.