Hyperactive and aggressive behaviors in childhood as related to low platelet monoamine oxidase (MAO) activity at adult age: A longitudinal study of male subjects

Aspects of childhood behavior were explored in relation to platelet monoamine oxidase (MAO) activity, which is considered a biological marker of vulnerability for disinhibition and psychosocial deviances, at adult age. Data were obtained from a group of 75 male subjects as (1) teacher ratings of behavior at ages 10 and 13 yr with respect to Motor Restlessness and Concentration Difficulties, the sum of which was used as an indicator of Hyperactive Behavior, and Aggressiveness, supposed to be concomitants in the developmental process behind later disinhibitory tendencies and different forms of psychosocial deviances, and (2) platelet MAO activity, used as an indirect indicator of central serotonergic activity, at age 26–27 yr. A pattern analysis (Configural Frequency Analysis, CFA) was applied. For the combination of being high in persistent Hyperactive Behavior and high in persistent Aggressiveness at an early age, and being low in platelet MAO activity at adult age, a highly significant type was obtained. Furthermore, results of loglinear modelling of Hyperactive Behavior and Aggressiveness in childhood and adult platelet MAO activity indicated a positive relationship between Hyperactive Behavior and Aggressiveness, and a negative association between Hyperactive Behavior and platelet MAO activity; those interactions were significant and contributed to a good model fit. There was no significant interaction effect between Aggressiveness and platelet MAO activity. The results of the analyses were used as a basis for some theoretical and methodological conclusions.