Platelet monoamine oxidase activity and tardive dyskinesia.

A few studies of chronic psychiatric inpatients have reported an inverse association between platelet monoamine oxidase (MAO) activity level and tardive dyskinesia (TD). In contrast to these earlier findings, we found no significant or consistent association between platelet MAO activity level and TD occurrence when we controlled for other TD predictors in a case-control study of 80 outpatients maintained on neuroleptic medications. We did find, however, that black subjects had significantly lower levels of MAO activity than did whites in an analysis controlling for age, sex, and neuroleptic dose.