Analysis by Age
To explore the possible effect of age, we decided to separate the groups by using 40 years as the cutoff point (18–40 years and ≥41). This point was chosen primarily because it was the mean and median age of our study group and because this is the age up to which suicide is the leading cause of death for men in Canada (49).
The prevalence rates of alcohol abuse/dependence in the last 6 months were significantly higher in younger depressed suicide completers than in younger depressed comparison subjects, and a nonsignificant higher proportion of younger depressed suicide completers had a positive history of drug abuse/dependence during the 6 months before their deaths. No other significant differences were found on current axis I diagnoses between younger and older depressed suicide completers (Table 3).
Lifetime prevalence rates of drug abuse/dependence were significantly higher in younger depressed suicide completers than in younger depressed comparison subjects but not in older depressed suicide completers compared to older depressed comparison subjects. There was a nearly significant difference between alcohol abuse/dependence among depressed suicide completers older than 40 compared to older depressed comparison subjects. No other significant differences were found on lifetime axis I diagnoses in younger or older depressed suicide completers (Table 3).
The prevalence rates of cluster B personality disorders were significantly higher in younger depressed suicide victims than in younger depressed comparison subjects but not in older cases, whereas no significant differences were found between younger and older depressed suicide victims compared to depressed comparison subjects for cluster A and cluster C personality disorders (Table 3). Nevertheless, interesting nearly significant differences were observed, particularly with regard to the effect of cluster C diagnoses in younger depressed suicide victims.
There was a marked effect of age on direct measures of impulsive and aggressive behaviors. In particular, the proportion of highly impulsive individuals, as well as mean scores of lifetime aggressive behaviors, were significantly higher in depressed suicide victims than in depressed comparison subjects only in the younger age group (Table 2).
Finally, we found that suicide completers 40 years and younger were using marginally more violent suicide methods (N=41, 85%) than suicide cases older than 40 (N=27, 66%) (odds ratio=3.04, 95% CI=0.98–10.00).