Nature vs Nurture

Aggressive behavior is influenced by variation in genes of the serotonergic circuitry and early-life experience alike. The present study aimed at investigating the contribution of polymorphisms shown to moderate transcription of two genes involved in serotonergic neurotransmission (serotonin transporter,5HTT, and monoamine oxidase A,MAOA) to the development of violence and to test for gene–environment interactions relating to adverse childhood environment. A cohort of 184 adult male volunteers referred for forensic assessment participated in the study. Each individual was assigned to either a violent or a nonviolent group. Logistic regression was performed and the best-fitting model, with a predictive power of 74%, revealed independent effects of adverse childhood environment andMAOAgenotype. High environmental adversity during childhood was associated significantly with violent behavior. Forty-five percent of violent, but only 30% of nonviolent individuals carried the low-activity, shortMAOAallele. Most interestingly, an interaction effect between childhood environment and5HTTgenotype on violent behavior was found in that high adversity during childhood impacted only the later-life violence if the short promoter alleles were present. These findings indicate complex interactions between genetic variation of the serotonergic circuitry and environmental factors arguing against simplistic, mono-causal explanations of violent behavior.

Keywords:violence, aggression, criminality, personality, monoamine metabolism, serotonin transporter

Top

INTRODUCTION

Aggression comprises heterogeneous neurobiological features and phenomenology. In consideration of apparently qualitative subtypes of aggression, a sensible construct was made in hypothesizing a dichotomy between an impulsive-reactive-hostile-affective subtype (defensive aggression) and a controlled-proactive-instrumental-predatory subtype (offensive aggression) ( Vitiello and Stoff, 1997). Although most...