Impulsivity and aggression in suicide across age and sex: case–control study

Background Impulsivity and aggression are known risk factors for suicide, with observed age and sex differences in their impact. Aims To explore variations in impulsivity and aggression based on sex and age and examine their roles in predicting suicide. Method We examined 582 participants (406 individuals who died by suicide, 176 non-suicidal sudden-death controls) using the psychological autopsy method. Measures of impulsivity and aggression included the Barratt Impulsiveness Scale (BIS) and the Brown-Goodwin History of Aggression (BGHA). Participants were categorised into four groups: suicide male, control male, suicide female and control female. For group comparisons, we used analyses of variance and Spearman's rank correlation to assess the relationship between age and BIS and/or BGHA ratings. Stepwise logistic regression was used to identify predictors of suicide for each sex. Results Higher levels of BIS and BGHA ratings were found in the suicide group compared with controls (BIS: 51.3 v. 42.2, P = 0.002, eta(2) = 0.017; BGHA: 7.1 v. 4.1, P < 0.001, eta(2) = 0.028), with no significant sex differences. BIS and BGHA ratings decreased with age in the suicide groups (suicide male: impulsivity rho = -0.327, P < 0.001; suicide female: aggression rho = -0.175, P = 0.038) but not among controls. Logistic regression analysis revealed that for men, aggression (odds ratio 1.072, 95% CI: 1.032-1.112) was a key predictor. For women, younger age (odds ratio 0.970, 95% CI: 0.948-0.993), low BIS impulsivity ratings (odds ratio 1.018, 95% CI: 1.001-1.036) and living with children (odds ratio 0.448, 95% CI: 0.208-0.966) were protective factors. Conclusions Impulsive and aggressive behaviours are critical factors in suicide risk among younger individuals, indicating an age effect but no sex dimorphism, with aggressive behaviours being a better predictor for men and impulsive and aggressive behaviours for women.