Panic disorder and social phobia: effects of comorbidity on familial transmission.

The aim of this study was to examine effects of comorbidity of panic disorder and social phobia on familial transmission of each of these disorders. Rates of panic disorder and social phobia were compared in directly interviewed relatives of four proband groups: (1) panic disorder, (2) social phobia, (3) panic disorder and social phobia, and (4) never ill controls. Anxiety disorder probands had no additional lifetime anxiety disorder comorbidity. The familial pattern of the comorbid (panic disorder and social phobia) probands resembled that of the panic disorder group: an increased rate of panic disorder but not social phobia as compared to relatives of controls. Relatives of social phobia probands had an increased rate of social phobia but not panic disorder. These data indicate that social phobia in individuals who subsequently develop panic disorder: (1) differs with respect to familial transmission from social phobia which occurs without lifetime anxiety comorbidity; and (2) may be nonfamilial and/or causally related to panic disorder. Additional studies in larger epidemiologic samples are required to assess generalizability of these findings.