Reduced Monoamine Oxidase Activity in Blood Platelets from Bipolar Depressed Patients

Cellular monoamine oxidase (MAO) activity measured in blood platelets is significantly (45 percent) lower in depressed patients with a history of mania (bipolar patients) than in nonbipolar depressed patients and normal controls of similar age and sex. This difference in MAO activity may be related to other biological and psychological characteristics of these patients that suggest that bipolar patients constitute a specific subgroup among patients with affective disorders.