Associations of multiple trauma types and MAOA with severe aggressive behavior and MAOA effects on training outcome Danique Smeijers a,b,n , Erik Bulten b , Barbara Franke a,b,e , Jan Buitelaar b,d,f , Robbert-Jan Verkes a,b,c a Department of Psychiatry, Radboud University Medical Center, The Netherlands b Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands c Forensic Psychiatric Centre Pompestichting, Nijmegen, The Netherlands d Karakter Child and Adolescent Psychiatry University Center, Nijmegen, The Netherlands e Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands f Department of Cognitive Neuroscience, Radboud University Medical Centre, Nijmegen, The Netherlands Received 13 December 2016; received in revised form 19 May 2017; accepted 20 June 2017 KEYWORDS Aggression; MAOA; Trauma Abstract Previous research showed that the disposition to react with disproportionate aggression in adults is influenced by an interaction between a variant in the X-chromosomal monoamine oxidase A gene (MAOA) and early traumatic events. Such studies have often focused on a single type of trauma, whereas we know that experiencing multiple trauma types is associated with more detrimental consequences. The differential susceptibility hypothesis suggests that individuals who are most susceptible to adversity, are also most likely to benefit from supportive experiences in childhood. Differences in susceptibility are thought to be partly genetically driven. In the present study we explored whether a genotype of MAOA linked to lower expression of the gene (MAOA-L) modified the effect of multiple types of trauma on aggression and/or altered responsiveness to treatment among adults with severe aggression. Forensic psychiatric outpatients (FPOs) (N = 150) receiving treatment for aggression regulation problems were recruited. Traumatic events and aggression were measured using self-report. FPOs with multiple trauma types and those with the MAOA-L allele reported more severe levels of aggression. No interaction effects between MAOA genotype and trauma emerged. There were no differences in response to the intervention between FPOs with and without the MAOA-L variant, whereas FPOs with a single type of trauma showed the slowest reduction of aggression. www.elsevier.com/locate/euroneuro http://dx.doi.org/10.1016/j.euroneuro.2017.06.016 0924-977X/& 2017 Elsevier B.V. and ECNP. All rights reserved. n Corresponding author at: Radboud University Medical Center Department of Psychiatry, (966) PO Box 9101, 6500 HB, Nijmegen, The Netherlands. E-mail address: daniquesmeijers@gmail.com (D. Smeijers). European Neuropsychopharmacology (]]]]) ], ]]]–]]] Please cite this article as: Smeijers, D., et al., Associations of multiple trauma types and MAOA with severe aggressive behavior and MAOA effects on training outcome. European Neuropsychopharmacology (2017), http://dx.doi.org/10.1016/j.euroneuro.2017.06.016