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, η² = 0.017; BGHA: 7.1 v. 4.1, P < 0.001, η² = 0.028), with no significant sex differences. BIS and BGHA ratings decreased with age in the suicide groups (suicide male: impulsivity ρ = -0.327, P < 0.001; suicide female: aggression ρ = -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.