Low platelet monoamine oxidase activity in Swedish imprisoned criminal offenders.

Numerous studies report a connection between low platelet monoamine oxidase activity (trbc MAO) and personality traits such as impulsiveness and sensation seeking. Generally, criminal offenders constitute a group of individuals that are high in such temperamental characteristics. In this study, we investigated trbc MAO activity in imprisoned criminal offenders and in controls where the confounding factor of smoking was under control. Radiometric MAO assays were performed in 99 male criminal offenders and in 60 non-criminal volunteers. Offenders had significantly lower trbc MAO activity than controls, i.e., 8.8 +/- 3.0 nmol/10(10) platelets/mm and 11.3 +/- 5.1, respectively (p<0.0001). When only smoking individuals were included in the analysis, the difference in trbc MAO was still statistically significant (p<0.05). Based on these data, we suggest that trbc MAO is related to mechanisms predisposing for development of specific personality characteristics that in turn increase vulnerability for criminal behaviour. The results also suggest that low trbc MAO activity in criminal offenders is not an artefact of cigarette smoking.