Low platelet MAO levels found in violent criminals

Studies link low levels of plate-let monoamine oxidase (MAO) activity to sensation seeking, monotony avoidance, and impulsive behavior, and a growing number of studies show a strong association between low platelet MAO and criminality.

In the latest of these studies, Håkan Garpenstrand and colleagues measured platelet MAO levels in 99 violent criminal offenders and in control subjects. The criminal offenders had significantly lower platelet MAO activity than other subjects, even when the researchers controlled for smoking (which lowers MAO levels).

Drug abusers were particularly likely to exhibit low MAO levels, and of those who abused opiates, only one had high platelet MAO. "Interestingly," the researchers say, "the temperamental characteristics previously associated with [platelet] MAO have also been connected to the presence of drug abuse as well as violent behavior."

Garpenstrand and colleagues note that dysfunction of the serotonin system is linked to impulsive behavior and criminality, and point out that there is a significant relationship between levels of platelet MAO and levels of the serotonin metabolite 5-HIAA. This and other findings, they say, have led researchers to hypothesize that platelet MAO "is related to the size or capacity of the central serotonin system."

In a previous study (see related article, Crime Times, 1997, Vol. 3, No. 2, Page 7), P. O. Alm and colleagues reported that delinquents with low MAO activity had a fourfold increased risk of chronic adult criminal behavior when compared to delinquents with high MAO activity.

"Low platelet monoamine oxidase activity in Swedish imprisoned criminal offenders," Håkan Garpenstrand, Eva Longato-Stadler, Britt af Klinteberg, Elena Grigorenko, Mattias Damberg, Lars Oreland, and Jarmila Hallman, European Neuropsychopharmacology, Vol. 12, 2002, 135-40. Address: Håkan Garpenstrand, Department of Neuroscience, Uppsala University, P.O. Box 593, BMC, 751 24 Uppsala, Sweden, haakan.garpenstrand@neuro.uu.se.