OCD has been shown to be associated with diseases of the basal ganglia. A significant number of children who developed Economo disease after an influenza epidemic early in the twentieth century experienced OCD symptoms, and there was a significant increase in the prevalence of chronic OCD in survivors of the epidemic. OCD has also been described in Huntington disease, parkinsonism, and carbon monoxide poisoning associated with destruction of the globus pallidus. There is a higher incidence of rheumatic fever in family members of patients with OCD. Adults with a history of Sydenham chorea have a higher incidence of OCD than does the population at large.
There is a high prevalence of vocal and motor tics in OCD (20%) and in the families of patients with OCD (20%). The full-fledged Tourette syndrome is present in only 5–7% of adult patients with OCD. Over 60% of children with OCD will experience at least transient tics, and as many as 15% will develop the full Tourette syndrome. For children with an early onset of symptoms, OCD may be the first manifestation of Tourette syndrome. OCD symptoms occur in 40–70% of individuals with Tourette syndrome and in 12% of family members of Tourette syndrome patients who do not themselves have Tourette syndrome.
OCD patients often have comorbid Axis I disorders. Depression is the most common secondary diagnosis in OCD. Approximately 50% of individuals with OCD will develop a major depressive episode in their lifetime. The depression occurs because OCD symptoms prevent the individual from carrying out activities important for self-esteem, and because attempts to resist the symptoms, or adequately meet the demands of the illness, inevitably fail. OCD can engender continual conflict with significant others and is often associated with social isolation. Effective treatment of the OCD in these cases often leads to resolution of the depressive episode.
Patients with OCD also have a high prevalence of panic disorder, secondary agoraphobia, social phobia, and alcohol and other substance abuse. Agoraphobia can result from a patients attempts to avoid circumstances that trigger obsessions. In some cases the patient may be trapped at home because he or she is unable to tolerate the obsessions and compulsions that are triggered by contact with the outside world.
Anxiety can complicate OCD, as the individual worries about both the consequences of having OCD and the consequences of being unable to complete compulsions. Patients with OCD may describe panic-like attacks that are not true panic attacks. Rather, they are attacks of severe anxiety related to violation of an obsessive concern. For example, when an individual who has contamination fears discovers that he or she has been severely contaminated, the individual may experience an overwhelming sense of dread, anxiety, and despair, related to the impossible task of decontaminating everything that he or she has defiled. This patient might mislabel these experiences as panic attacks. The clinician must be aware of this process to avoid unnecessarily complicating the patients diagnostic picture.
There is also a high prevalence of personality disorders in patients with OCD (50–70%). Avoidant, dependent, borderline, histrionic, and schizotypal personality disorders occur most frequently. OCPD occurs in only a small minority of patients, with estimates as low as 6% of OCD cases. This observation argues against an older view that OCD was an extreme variant of OCPD. Interestingly, although personality disorder symptoms are thought to be life-long fixed traits, effective treatment of OCD will eliminate personality disorder symptoms in a majority of OCD patients, suggesting that the dysfunctional Axis II symptoms may in part be secondary to stress and tension associated with the Axis I disorder.
The diagnosis of avoidant personality disorder may be secondary to the individuals primary pathology, combined with an ambiguity in the DSM-IV-TR diagnostic criteria for the personality disorder. An unreasonable concern of being the target of disapproval of others is a DSM-IV-TR criterion for avoidant personality disorder. Individuals with OCD who fear they may be responsible for something bad happening may also fear that they will be the subject of consequent disapproval or ridicule. These patients have unreasonable concerns that they might in fact be at fault. Individuals with the true personality disorder (i.e., those who do not have OCD) are unreasonably hypersensitive to the criticism itself. As individuals with OCD improve they often no longer meet criteria for this diagnosis.
Likewise, the dependent personality disorder can occur in patients with OCD who feel that they need assistance from others in carrying out their compulsions or who need reassurance that their obsessive concerns are not valid. Such assistance relieves them of the responsibility for carrying out acts that might have dreadful consequences. These individuals are dependent on their significant other, and they experience significant discomfort when that person is not available for these purposes. These patients will meet criteria for this personality disorder as a result of the nature of their OCD. As their OCD improves, many will no longer meet criteria for this diagnosis.