Monoamine oxidase A genotype is associated with gang membership and weapon use.

CONTEXT A functional polymorphism in the promoter region of the monoamine oxidase A (MAOA) gene has been found to be associated with a broad range of antisocial phenotypes, including physical violence. At the same time, it is well known that gang members represent some of the most serious violent offenders. Even so, no research has ever examined the association between MAOA and gang membership. OBJECTIVES The aim of this study is to examine the association between MAOA and gang membership and between MAOA and weapon use. DESIGN We examined the effects of MAOA by using a molecular genetic association research design. SETTING A nonclinical sample was used in this study. PARTICIPANTS Participants were drawn from the National Longitudinal Study of Adolescent Health (1155 females, 1041 males). MAIN OUTCOME MEASURES The outcome measures of this study are gang membership and weapon use. RESULTS The low MAOA activity alleles conferred an increased risk of joining a gang and using a weapon in a fight for males but not for females. Moreover, among male gang members, those who used weapons in a fight were more likely to have a low MAOA activity allele when compared with male gang members who do not use weapons in a fight. CONCLUSIONS Male carriers of low MAOA activity alleles are at risk for becoming a gang member and, once a gang member, are at risk for using weapons in a fight.