UNDERSTANDING THE COMORBIDITY BETWEEN EARLY-ONSET DYSTHYMIA AND CLUSTER-B PERSONALITY-DISORDERS - A FAMILY STUDY

Objective: A number of studies have documented significant comorbidity between dysthymia and axis II personality disorders, particularly tho se grouped in cluster B. However, the nature of this comorbidity is po orly understood. The purpose of this investigation was to use the fami ly study method to test five competing models of the comorbidity betwe en early-onset dysthymia and cluster B personality disorders. Method: Proband groups consisted of subjects with early-onset dysthymia and a co-occurring cluster B personality disorder (N=28), subjects with earl y-onset dysthymia without a cluster B personality disorder (N=69), and a comparison group of subjects who had never been psychiatrically ill (N=45). The groups were compared on rates of dysthymia with a cluster B personality disorder, dysthymia without a cluster B personality , a nd cluster B personality disorders without dysthymia in their first-de gree relatives (N=675). Results: The relatives of both subgroups of dy sthymic probands exhibited higher rates of dysthymia with a cluster B personality disorder, dysthymia without a cluster B personality disord er, and cluster B personality disorders without dysthymia than the rel atives of the never ill probands. In addition, the relatives of proban ds with comorbid dysthymia exhibited higher rates of cluster B persona lity disorders without dysthymia than the relatives of probands with n oncomorbid dysthymia. Conclusions: This pattern of results is consiste nt with the notion that dysthymia and cluster B personality disorders co-occur because of shared etiological factors. This was the only one of five models of the comorbidity between dysthymia and cluster B pers onality disorders that was supported by the family data.