Platelet monoamine oxidase activity in subgroups of schizophrenic disorders.

This article summarizes findings from a series of studies that examined platelet monoamine oxidase (MAO) activity in patients with nonaffective schizophrenic disorders and schizophrenia-related depressions. The findings indicate that mean platelet MAO activity was not different from control values in the subgroup of nonaffective schizophrenic disorders without auditory hallucinations (that is, the S-1 subgroup). However, mean platelet MAO activity was reduced in the subgroup of nonaffective schizophrenic disorders characterized by the presence of auditory hallucinations often occurring in conjunction with paranoid features (that is, the S-2 subgroup). Moreover, we found that mean platelet MAO activity was increased in schizophrenia-related depressions characterized by histories of chronic asocial, eccentric, or bizarre behavior.