Psychiatric vulnerability, monoamine oxidase, and the average evoked potential.

College students in two separate studies had platelet monoamine oxidase (MAO) activity determinations and average evoked potential (AEP) measurements taken. On the basis of Minnesota Muliphasic Personality Inventory (MMPI) or Research Diagnostic Criteria (RDC) evaluations, psychopathology, particularly affective disorder, was found to be more prevalent among both persons with the combination of low MAO activity and AEP augmenting and those with high MAO activity and AEP reducing. The same pattern is apparent whether students were selected for extremely high or low MAO activity (study 1) or for elevated or normal MMPI scores (study 2). Some psychiatric patient groups also show this pattern. An interactive model of sensation-seeking and sensory inhibition is presented.