Hypochondriasis and its relationship to obsessive-compulsive disorder.

Hypochondriasis is a heterogeneous disorder. This was well demonstrated in the study by Kellner et al, which showed that patients with high levels of disease fear tended to be more anxious or phobic, whereas patients with high levels of disease conviction tended to have more and more severe somatic symptoms. Little comorbidity exists to support the statement that hypochondriasis is an obsessive-compulsive spectrum disorder. Although patients exist whose hypochondriac concerns are identical in quality to the intrusive thoughts of patients with OCD, as a group, patients with hypochondriasis do not share a comorbidity profile comparable with that of patients with OCD. The data support a closer relationship between hypochondriasis and somatization disorder than between hypochondriasis and OCD. The family history data is limited by the lack of adequate studies. Using comparable methods of the family history approach, Black's study reported a higher frequency of GAD but not OCD among the relatives of OCD patients--a finding similar to what Noyes found among the relatives of hypochondriac patients; however, using the direct interview method, somatization disorder was the only statistically more common disorder, among relatives of female hypochondriac patients. Therefore, although the parallel in overlap with GAD is suggestive of a commonality between OCD, GAD, and hypochondriasis, the finding of a greater frequency of somatization disorder leans against the hypothesis that hypochondriasis is best considered an OCD spectrum disorder. The pharmacologic treatment data are the one type of biologic evidence that supports a bridge to OCD. The pharmacologic studies suggest that for patients with general hypochondriasis, TCAs are not effective and that higher dosages and longer trials of the SRIs are needed. These pharmacologic observations are comparable with the ones made for patients with OCD but dissimilar to the observations made for depression. The benefit of imipramine among patients with illness phobia must be assessed in placebo-controlled trials among illness phobics and among hypochondriacs. Even more valuable would be a direct comparison of a TCA (e.g., imipramine or desipramine) and a selective SRI (e.g., fluoxetine) to determine whether the response to selective SRIs is greater. Although the pharmacologic data are compelling in supporting the hypothesis that hypochondriasis is an obsessive-compulsive spectrum disorder, the comorbidity data are equally compelling in dispelling that hypothesis. Perhaps future studies clarify the subtypes of hypochondriasis, be they "phobic, obsessive, and depressive," "chronic and episodic," "early onset versus late onset" or some other as yet undetermined subtype. Such clarification may be aided by better instruments to assess the obsessive-compulsive and hypochondria spectrums within individuals and families and by neuropsychological or pharmacologic challenge and neuroimaging studies.