Personality traits related to monoamine oxidase activity in platelets.

Platelet monoamine oxidase (MAO) activity and intellectual level were examined in a large series of 1,129 18-year-old boys, selected from the general population. Personality traits were determined by means of selected subscales from several personality inventories such as the Zuckerman Sensation Seeking Scale, the Eysenck Personality Inventory, and the Karolinska Hospital Personality Inventory. Information was also gathered concerning alcohol consumption habits, signs of alcohol dependence, and use and abuse of tobacco, cannabis, glue, opiates, and amphetamine. Low MAO subjects were found to be more sensation seeking and to have higher scores on impulsivity and monotony avoidance. They also had higher use of tobacco and alcohol, showed more signs of possible alcohol dependence, and showed more drug abuse. When low MAO subjects were subdivided according to intellectual level, low MAO subjects with high intellectual level were found to have higher psychological functioning as judged by a psychologist after a clinical interview. Low MAO subjects with low intellectual level were found to have more use and abuse of alcohol and drugs, i.e., less accepted forms of sensation seeking, and they had a significantly lower level of psychological functioning. This subgroup seems to be the real "high risk" group that according to the high risk paradigm could be expected to show more alcohol abuse and higher tendencies to suicidal behavior.