Platelet monoamine oxidase activity and psychometric correlates in male violent offenders imprisoned for homicide or other violent acts

Violent behavior has been associated with certain personality traits like poor impulse control, sensation seeking, and monotony avoidance, which predispose to increased risk for violent acts. Low platelet monoamine oxidase (MAO) activity has been found in subjects with such traits, as well as in imprisoned violent offenders. On the other hand, cigarette smoking is expected to inhibit MAO activity. We assessed impulse control, lifetime history of aggression, suicide risk, as well as platelet MAO activity in 82 male offenders (mean age 33.0 +/- 10.7 years) imprisoned for homicide or other violent acts, and in 54 control male subjects (mean age 35.1 +/- 6.6 years). General psychopathology was assessed by the Hopkins Symptom Check List (SCL-90) questionnaire. A high rate of smoking (89 %), significantly higher than controls (63 %), was observed in offenders, but there were no differences in MAO activities among nonsmokers, moderate, or heavy smokers in either group. Offenders showed significantly higher scores in Impulse Control, Past Feelings and Acts of Violence, Suicide Risk and SCL-90 scales. Offenders who had committed other violent acts than homicide had higher scores in the three psychometric scales and in the Depression, Obsessive-Compulsive, Hostility, and Anxiety subscales of the SCL-90, than offenders who had committed homicide. Platelet MAO activity was significantly lower (p = 0.01) in the offenders' group (38.1 +/- 14.4) compared to controls (44.7 +/- 15.2). The difference could not be attributed to smoking, and seems to be related to personality traits and behaviors that characterize the offenders' group.