Platelet monoamine oxidase and plasma amine oxidase in psychiatric patients.

Platelet monoamine oxidase (MAO) and plasma amine oxidase (PAO) activities were determined in 70 normal controls and 76 psychiatric patients. Platelet MAO activity did not differ between the normal controls and patients diagnosed as schizophrenic or primary affective illness, although there was a strong trend for chronic schizophrenics to have lower MAO activity. Schizophrenic patients with Schneiderian-type hallucinatiions had significantly lower MAO activity than normal controls or schizophrenic patients who did not hallucinate. There was no relationship between hallucinations and platelet MAO activity in patients with affective psychoses. Paranoid schizophrenics did not have significantly different MAO activity from nonparanoid schizophrenics. PAO activity was generally lower in all diagnostic groups than in normal controls, but the results were statistically significant only for acute schizophrenics.