Factors associated with decreased platelet MAO activity in chronic schizophrenics.

Platelet MAO activity was determined in a sample of chronic schizophrenics, including drug-free and neuroleptic-treated patients, and in a normal control group. Patients with MAO values below and above the median were compared with respect to several clinical, historical, neuroradiological and neuropsychological variables. The enzyme activity was significantly decreased in the whole patient group and in the subgroup of neuroleptic-treated patients, but not in the subgroup of drug-free patients. The only significant difference between low MAO and high MAO patients concerned drug status (higher percentage of patients on neuroleptics in the former subgroup). On stepwise discriminant function analysis, drug status (on neuroleptics vs. off neuroleptics) correctly classified 63.4% of patients.