Descriptive Psychopathology: The Signs and Symptoms of ...

389 Chapter 16: An evidence-based classificationand pathological gambling are co-occurring. Non-melancholic depression is alsoco-occurring but does not appear to be part of the OCD pathophysiology. 138OCD warrants its own category of OCD spectrum disorders.The OCD spectrum is seen as several clusters – somatic: body image, hypochondriasis,body dysmorphic disorder, anorexia nervosa, and binge eating;impulse control: some persons with pathological gambling, some paraphilias,trichotillomania, kleptomania, and self-injury; and repetitive movement: Gillesde la Tourette’s syndrome, and Sydenham’s chorea. 139Non-melancholic depression (about 20% of patients) is the most commonco-occurring condition with OCD. This prevalence is modestly higher than baserates for non-melancholic depression and may reflect demoralization from theOCD and the low bar for the diagnosis of depression in present criteria. 140 Socialphobia is also common, but the prevalence rates for other anxiety disorders arewithin the estimated population base rates (0–10%). 141 In contrast, the prevalencerates for co-occurring spectrum conditions are greater than estimatedpopulation base rates (e.g. 5–10% for anorexia nervosa, body dysmorphic disorder,hypochondriasis, and trichotillomania, 5% for sexual compulsions, and2–4% for Gilles de la Tourette’s syndrome). In patients with these spectrumconditions the prevalence rates of OCD is also high. 142 In contrast, patients withanxiety disorder have low rates of the spectrum conditions. 143Family and twin studies find substantial heritability for OCD (about 50%). 144Family, twin and molecular genetic studies, however, are inconclusive, offeringlittle help in resolving the classification of OCD. While increased rates of OCD,anxiety disorders, and mood disorders are reported in the first-degree relatives ofpatients with OCD, 145 other studies, while finding higher rates of OCD inrelatives of OCD patients, find rates of anxiety disorders and mood disorderssimilar to those of the general population. 146 The separation of depression intomelancholia and non-melancholia disorders may clarify this contradiction.Hollander and colleagues conclude from their review that “most anxiety disordersand affective disorders do not have a familial relationship with OCD”. 147The lifetime risk for tic disorders and Gilles de la Tourette’s disorder (GTS) isalso greater in relatives of patients with OCD. 148 The prevalence rates of OCDspectrum disorders are also higher in the first-degree relatives of patients withOCD than in controls, 149 as are the rates of spectrum conditions in the relatives ofpatients with OCD spectrum. Higher rates of classic OCD are reported in therelatives of patients with trichotillomania 150However, no increased risk in relatives of OCD patients is found for eatingdisorders, but anorexia and bulimia are not separated, 151 and others have foundan increased risk for OCD spectrum in the relatives of patients with eatingdisorder. 152