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

Abstract

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 (LA LA ), intermediate (LA LG , SLA ) activity variants were more likely to have exhibited self-directed aggression relative to the low activity (LG LG , 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.

Keywords: 5-HTTLPR genotype; BGHA; CTQ; childhood trauma; externalizing behaviors; extraversion; prisoners; self-directed aggression; self-mutilators; serotonin transporter gene polymorphism; suicide attempters.

© 2016 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

Figures

Fig 1. Independent effects of 5HTTLPR on self-directed aggressive behavior

Contingency analysis of self-directed aggressive behavior by 5-HTTLPR functional activity variants shows a variant dosage effect (L-R χ2 = 8.5, p=0.014; Pearson χ2 = 8.1, p=0.017). Triallelic 5-HTTLPR genotypes were grouped as low activity (SS, SLG, LGLG), intermediate activity (SLA, LALG) and high activity (LALA) variants.