1. ¹Department of Psychology, Yale University, New Haven, CT, USA
2. ²Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, UK
3. ³Department of Psychology, University of Wisconsin at Madison, Madison, WI, USA

Correspondence: Dr J Kim-Cohen, Department of Psychology, Yale University, PO Box 208205, New Haven, CT 06520, USA. E-mail: julia.kim-cohen@yale.edu

Received 17 November 2005; Revised 12 May 2006; Accepted 17 May 2006; Published online 27 June 2006.

Abstract

Previous research on adults has shown that a functional polymorphism in the promoter region of the monoamine oxidase A (MAOA) gene moderates the impact of childhood maltreatment on risk for developing antisocial behavior. Thus far, attempts to replicate this finding have been mixed. The current study (i) presents new data investigating this finding in a sample of 975 seven-year-old boys, and (ii) evaluates the extant data by conducting a meta-analysis of published findings. We replicated the original finding by showing that the MAOA polymorphism moderates the development of psychopathology after exposure to physical abuse, we extended the finding to childhood closer in time to the maltreatment experience, and we ruled-out the possibility of a spurious finding by accounting for passive and evocative gene–environment correlation. Moreover, meta-analysis demonstrated that across studies, the association between maltreatment and mental health problems is significantly stronger in the group of males with the genotype conferring low vs high MAOA activity. These findings provide the strongest evidence to date suggesting that the MAOA gene influences vulnerability to environmental stress, and that this biological process can be initiated early in life.