Relationship of auditory hallucinations and paranoia to platelet MAO activity in schizophrenics: sex and race interactions.

Platelet monoamine oxidase (MAO) activity was determined in 37 female and 64 male patients with Research Diagnostic Criteria diagnoses of paranoid or undifferentiated schizophrenia, or schizoaffective disorder, mainly schizophrenic, and for 71 female and 65 male normal controls (NCs). Female NCs had significantly higher adjusted mean platelet MAO activity than male NCs and female, paranoid, nonhallucinating schizophrenics. Male NCs had significantly higher adjusted mean platelet MAO activity than male, paranoid, hallucinating schizophrenics. Examination of main and interactive effects of diagnostic subtype, presence/absence of auditory hallucinations, gender, and race within the group of schizophrenic patients revealed no statistically significant main effect but, rather, significant interactive effects of auditory hallucinations with gender, with diagnostic group and gender, and with diagnostic group and race in the prediction of platelet MAO activity. The interaction of diagnostic subtype with race and gender in the prediction of platelet MAO activity was also statistically significant. In general, significantly decreased platelet MAO activity was associated with both paranoid subtype and presence of auditory hallucinations in male and in black schizophrenics; and with paranoid subtype alone in white male schizophrenics. These interactive relationships with platelet MAO activity in schizophrenics may account for discrepancies in previous reports of the activity of this enzyme in schizophrenics, and are consistent with reduced platelet MAO activity in subgroups of schizophrenics.