Predictors for self-directed aggression in Italian prisoners include externalizing behaviors, childhood trauma and the serotonin transporter gene polymorphism 5-HTTLPR

Suicidal behavior and self-mutilation can be regarded as the expression of self-directed aggression and both are common in prison populations. We investigated the influence of externalizing behaviors, depressive symptoms, childhood trauma, 5-HTTLPR variants on self-directed aggression (N=145) in a group of 702 male Italian prisoners. Participants were comprehensively evaluated, including for psychiatric disorders, impulsive traits, lifetime aggressive behavior [Brown-Goodwin Lifetime History of Aggression (BGHA)], hostility, violent behavior during incarceration, depressive symptomatology [Hamilton Depression Rating Scale (HDRS)], childhood trauma [Childhood Trauma Questionnaire (CTQ)]. Logistic regression analysis showed false discovery rate corrected independent main effects of externalizing behaviors: BGHA (P=0.001), violent behavior in jail (P=0.007), extraversion (P=0.015); HDRS (P=0.0004), Axis I disorders (P=0.015), CTQ (P=0.004) and 5-HTTLPR genotype (P=0.02). Carriers of 5-HTTLPR high (LALA), intermediate (LALG, SLA) activity variants were more likely to have exhibited self-directed aggression relative to the low activity (LGLG, SLG, SS) variant: high/low: odds ratio (OR)=2.3, 95% confidence interval (CI) 1.27-4.68, P=0.007; intermediate/low: OR=1.96, 95% CI 1.09-3.68, P=0.025. The CTQ main effect was driven by physical abuse. There was no interactive effect of 5-HTTLPR and CTQ. Secondary logistic regression analyses in (1) all suicide attempters (N=88) and (2) all self-mutilators (N=104), compared with controls showed that in both groups, childhood trauma (P=0.008-0.01), depression (P=0.0004-0.001) were strong predictors. BGHA, violent behavior in jail predicted self-mutilation (P=0.002) but not suicide attempts (P=0.1). This study was able to distinguish differing influences on self-directed aggression between groups of closely related predictor variables within the externalizing behavioral domain. 5-HTTLPR had an independent, variant dosage effect.