Platelet monoamine oxidase activity in schizophrenic patients.

The authors studied platelet monoamine oxidase (MAO) activity in 29 schizophrenic inpatients and 26 schizophrenic outpatients during a 4-week double-blind trial of chlorpromazine with imipramine or thiothixene with placebo. The found that significantly more schizophrenic patients than normal control subjects had low platelet MAO activity after 4 weeks. Outpatients with low MAO activity were distinguished by increased behavioral activity and reduced social apathy. Inpatients with low MAO activity were distinguished by severity of illness and symptoms. Hallucinations were significantly more frequent among patients with low MAO activity. The authors suggest that platelet MAO activity might decline in some actively schizophrenic patients as part of the psychotic process.