MAO activity, csf amine metabolites, and drug-free improvement in schizophrenia.

Platelet monoamine oxidase (MAO) activity and amine metabolites in cerebrospinal fluid were compared in 22 schizophrenic patients, 8 of whom improved during a 30-day drug-free period. CSF 5-hydroxyindoleacetic acid and homovanillic acid did not distinguish between drug-free improvers and nonimprovers. However, drug-free improvers had lower platelet MAO activities than did normal controls. The authors suggest that looking at clinical variables in patients with low MAO activity might provide a means of biologically subtyping schizophrenic patients.