Clinical Correlates and Familial Aggregation of Age at Onset in Bipolar Disorder

Age at onset is associated with clinical heterogeneity in bipolar disorder and aggregates, possibly along with drug abuse, within families. These findings are consistent with the conclusion that age at onset reflects underlying genetic heterogeneity in bipolar disorder. Thus, age at onset may conceivably be used to identify more homogeneous groups of bipolar disorder families and thereby facilitate the mapping of bipolar disorder susceptibility genes.