Specificity of familial transmission of anxiety and comorbid disorders.

This study examines the specificity and impact of comorbid disorders in probands on the familial transmission of panic and social anxiety disorders. It employs a contemporary family study design with 225 probands (with and without panic and social anxiety disorders) sampled from outpatient clinics and the local community. Their 1053 adult first-degree relatives were assessed for lifetime disorders, based on best estimate diagnoses derived from semi-structured psychiatric diagnostic interviews (Schedule for Affective Disorders and Schizophrenia), multi-informant family history information, and medical records. Generalized estimating equations were used to examine the familial aggregation of panic and social anxiety disorders, and the contributions of comorbid disorders. Results show specificity of familial aggregation of both panic disorder and social anxiety in probands and relatives (i.e., panic odds ratio=3.7, 95%CI 1.5-9.3; social anxiety odds ratio=1.8, 95%CI 1.1-2.9) after controlling for comorbid disorders. There was no contribution of common comorbid disorders (depression, alcoholism, generalized anxiety disorder and agoraphobia) in probands on the familial aggregation of either disorder. These findings confirm prior studies of specificity of familial transmission of panic and social anxiety disorders, and demonstrate that the association between these disorders in probands is not attributable to comorbid mood, anxiety or substance use disorders. Therefore, despite the high magnitude of co-occurrence of panic disorder and social anxiety, there may be distinct etiologic factors underlying each disorder. These findings have implications for studies of the etiology, genetics, and treatment of these disorders.