Psychological characteristics corresponding to low versus high platelet monoamine oxidase activity.

From an original sample of 375 college students and employees studied for platelet MAO activity, 66 subjects representing the lower and upper deciles of the sample were contacted for further study, including administration of the booklet form of the MMPI. We analyzed what psychological characteristics might be associated with differences in MAO activity and attempted to cross-validate these characteristics by using them to predict the separability of low vs. high MAO subjects. Each subject was randomly assigned to one of two groups in which the low and high MAO subjects were balanced for sex. For 16 women in group A, a MAO scale discriminated low and high subjects with 100% accuracy. For 18 men in group A, a separate MAO scale discriminated with 94% accuracy. To cross-validate these results, the two scales were applied to another population; both discriminated low and high MAO women and men with a combined 97% accuracy. The thematic content of the two scales is discussed in the light of other reports on the psychological characteristics of low and high MAO subjects, including the apparent relationship between the scale content and the clinical features of bipolar affective disorder.