Reduced MAO Activity in First-Degree Relatives of Individuals With Bipolar Affective Disorders

Previous reports have indicated that platelet monoamine oxidase (MAO) activity is reduced in patients with the bipolar form of major affective illness. We present evidence that platelet MAO activity is also significantly reduced in the first-degree relatives of bipolar patients. However, platelet MAO activity did not distinguish ill from well family members. It is possible that reduced platelet MAO may be an indicator of increased familial vulnerability to affective disorders.