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Obsessive-compulsive and related disorders are characterized by obsessive, intrusive thoughts (e.g. constantly worrying about staying clean, or about one's body size) that trigger related, compulsive behaviors (e.g. repeated hand-washing, or excessive exercise). These behaviors are performed to alleviate the anxiety associated with the obsessive thoughts. These types of disorders can restrict participation in everyday life and/or generate significant distress, for instance, by making it difficult to leave the house without many repetitions of a compulsive behavior (e.g. checking that the doors are locked). Periodically experiencing worry or having a few "idiosyncratic" habits does not constitute an obsessive-compulsive or related disorder. Instead, these disorders are characterized by unusually high levels of worry and related compulsive behaviors, in comparison with a typical range of individuals.
Physical Symptoms: People with panic disorder may also have irritable bowel syndrome, characterized by intermittent bouts of gastrointestinal cramps and diarrhea or constipation, or a relatively minor heart problem called mitral valve prolapse, which can trigger panic attacks in some people. In fact, panic disorder often coexists with unexplained medical problems, such as chest pain not associated with a heart attack or chronic fatigue.
Genetics and family history (e.g., parental anxiety) may predispose an individual for an increased risk of an anxiety disorder, but generally external stimuli will trigger its onset or exacerbation. Genetic differences account for about 43% of variance in panic disorder and 28% in generalized anxiety disorder. Although single genes are neither necessary nor sufficient for anxiety by themselves, several gene polymorphisms have been found to correlate with anxiety: PLXNA2, SERT, CRH, COMT and BDNF. Several of these genes influence neurotransmitters (such as serotonin and norepinephrine) and hormones (such as cortisol) which are implicated in anxiety. The epigenetic signature of at least one of these genes BDNF has also been associated with anxiety and specific patterns of neural activity.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).