Lymphocyte monoamine oxidase activity and chronic schizophrenia

Lymphocyte monoamine oxidase (MAO) activity was assayed in 62 chronic schizophrenic patients, 113 normal volunteers, and 23 first-degree relatives of schizophrenic patients. Mean lymphocyte MAO activity was significantly lower (p < 0.001) in the chronic schizophrenic group than in controls; first-degree relatives had a mean lymphocyte MAO activity midway between the schizophrenics and normals. No relationship was found between lymphocyte MAO activity and sex or age of subjects. When subjects were subgrouped by race, blacks had significantly lower MAO activity than whites (p < 0.001).