CRIMINALITY AND PLATELET MONOAMINE-OXIDASE ACTIVITY IN FORMER JUVENILE DELINQUENTS AS ADULTS

Platelet monoamine oxidase (MAO) activity was estimated in 70 former d elinquent boys and 40 controls now aged 38-46 years. Platelet MAO acti vity was compared with their early criminal behaviour (before the age of 15) and their late registered criminality from the age of 15). Mean platelet MAO activity in subjects with both early and late criminalit y was significantly lower than that in former delinquents without late criminality. There was no significant difference in mean platelet MAO activity between controls and delinquents with early but no late crim inality. When delinquents with early criminality were divided into a l ow and a high MAO group, the relative risk to be registered for late c riminality was about 3.1 times higher for the subjects in the low MAO group. Thus, individuals with low platelet MAO activity run an increas ed risk of continued criminal behaviour.