Anticipation and imprinting in Japanese familial mood disorders.

Several reports have suggested the presence of anticipation and imprinting in Caucasian families with either unipolar or bipolar affective disorders. In practice, families consisting of subjects with bipolar and unipolar affective disorders are common, whereas unipolar cases were not included in the analysis because of their uncertain diagnostic status. The purpose of this study is to determine if anticipation and imprinting are associated with Japanese familial mood disorders. The age of onset, clinical course rating, single/recurrent disease episodes, number of hospitalizations, and number of suicide attempts were compared between two generations in 26 Japanese families with mood disorders [offspring/parental: unipolar (U/U), 14; bipolar/unipolar (B/U), 12]. A significantly lower age of onset and more recurrent episodes were observed in the offspring generation than in the parental generation in both U/U and B/U families. Our results suggest the presence of anticipation in both Japanese U/U and B/U families with mood disorders.