a1 Department of Psychiatry and the Department of Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, VA; the Institute for Social Research, University of Michigan, Ann Arbor, MI; Department of Psychiatry, Washington University School of Medicine, St Louis, MO, USA
Previous studies based on probands from clinical samples suggest that panic disorder aggregates strongly in families and may be due to a highly penetrant single major locus. In this study we examine panic disorder as assessed at blind, structured psychiatric interview in 2163 women from a population-based twin registry. DSM-III-R diagnoses were assigned at a narrow and at a broad level both by clinician review and by computer algorithm. The familial aggregation of panic disorder in this sample was only modest. The relatively small number of affected individuals prevented a definitive resolution of competing genetic and non-genetic models of familial transmission. Although there was some inconsistency across diagnostic approaches, most results suggested that the familial aggregation of panic disorder was due largely to genetic factors. Using a multifactorial-threshold model, the best estimates of the heritability of liability ranged from 30 to 40%. From a familial perspective, panic disorder with phobic avoidance appears to represent a more severe form of the syndrome than panic disorder without avoidance. Our results, which suggest that in the general population panic disorder is only a moderately heritable condition, are at variance with results from several previous investigations based on clinically ascertained samples.
c1 Address for correspondence: Dr Kenneth S. Kendler, Box 710, MCV Station, Richmond, VA 23298–0710, USA.