Episode frequency a familial trait in bipolar affective disorder

The authors of a recent study conclude that episode frequency is a familial trait in bipolar affective disorder and is an important clinical feature of the condition.The authors analysed data on 625 subjects from 86 families ascertained for a genetic linkage study of bipolar affective disorder. Families were ascertained through a proband with a reported history of bipolar I disorder and at least two first-degree relatives with a major affective disorder.All subjects were interviewed using the Schedule for Affective Disorders and Schizophrenia - Lifetime Version (SADS-L). Diagnoses among the 407 subjects with a major affective disorder included bipolar I disorder (23% [n=144]), bipolar II disorder (24.2% [n=151]), recurrent unipolar depression (16.2% [n=102]) and schizoaffective disorder, bipolar type (1.6% [n=10]).Episode frequency was calculated according to the total number of reported episodes of major depression, mania, or hypomania per year of illness.The authors observed a significant association between episode frequency and diagnostic group, with the greatest frequency observed in the bipolar II disorder group and the lowest in the recurrent unipolar depression group.In addition, a significantly higher episode frequency was observed in subjects with psychosis compared with those who had no such history.Significant associations between episode frequency and alcoholism and a history of suicidal behaviour were also observed. Episode frequency did not vary significantly between men and women and was not associated with panic disorder or substance abuse.The authors state that episode frequency was significantly correlated among probands and their affected relatives, suggesting that more than 30% of the variance in episode frequency was accounted for by family membership.According to DSM-IV criteria, 11.1% of subjects (n=46) experienced rapid cycling. The authors report that their data do not support DSM-IV rapid cycling as the best predictor of familiality or severity.The authors conclude that episode frequency is a familial trait in bipolar disorder, which is not accounted for by other, correlated variables (eg, alcoholism)."We suggest that episode frequency is an important clinical feature of bipolar affective disorder, with implications for severity, co-morbid conditions, and genetic research."Reference...