Platelet monoamine oxidase in schizophrenia and manic-depressive illness.

Monoamine oxidase (MAO) is an important enzyme in the catabolism of brain biogenic amines. Platelet MAO has been reported to be moderately reduced in manic-depressive patients and markedly reduced in schizophrenic patients. This enzyme's activity has been shown to be under a large degree of genetic control and has been proposed as a 'genetic marker' in schizophrenia. A transcultural replication of the finding of low platelet MAO in schizophrenia and manic-depressive illness was carried out at the Jerusalem Mental Health Centre. Manic-depressive patients were found to have higher platelet MAO activity than schizophrenic patients, as reported previously, but control individuals were as low as the schizophrenic patients. It is unlikely that platelet MAO activity is a transculturally-valid marker for schizophrenia.