The impact of alcohol use disorder and PTSD comorbidity on risk of suicide attempt.

BACKGROUND

Alcohol use disorder (AUD) and posttraumatic stress disorder (PTSD) are frequently comorbid and are individually associated with increased risk of suicidal behavior. However, whether their comorbidity exacerbates this risk has not been adequately investigated.

METHODS

Using a Swedish birth cohort (born 1970-1990; N = 799,203-858,983), we employed Aalen's linear hazards models to evaluate the risk of non-fatal suicide attempt (SA) as a function of registration for AUD and/or PTSD. Models were stratified by sex and considered the temporal ordering of AUD and PTSD. We adjusted for registrations of major depression (MD) and other key covariates.

RESULTS

The overall incidence of SA ranged from 16.52 to 19.29 per 10,000 person-years (PY). In models adjusted for MD and other covariates, PTSD accounted for an additional 12.19-22.09 SA cases per 10,000 PY; the corresponding range for AUD was 43.24-80.04, and the difference in effect size across predictors was more pronounced where AUD preceded PTSD. Comorbidity exacerbated risk: The interaction between PTSD and AUD accounted for 71.13-179.41 additional SA cases per 10,000 PY. In secondary models, interactions between AUD and MD conferred additional SA risk (40.50-127.88 additional SA cases per 10,000 PY), while interactions between PTSD and MD were very weak and, in most cases, negative (-13.26-3.29).

CONCLUSIONS

PTSD and AUD are independently associated with SA, but risk is substantially exacerbated among comorbid individuals. While the total effect of these conditions on SA risk is overall comparable across sexes, females whose PTSD precedes AUD are particularly burdened by comorbidity.