Background Suicide is a leading cause of death worldwide with rates of suicide higher in Northern Ireland (NI) compared to the rest of the UK and Ireland. In addition, the consumption of psychotropic medication is increasing. The association between psychotropic medication and suicide risk is contested. Existing population-based studies that have examined whether types of psychotropic medications are associated with suicide are either restricted to older populations or have investigated each medication separately rather than comparing them directly to one another. This study examined the association between psychotropic medication types and death by suicide across the whole adult population.

Methods A cohort of 1,115,647 individuals aged 18–75 was identified from the 2011 Census records, linked to prescription records for the five months surrounding the census and followed until the end of 2015 to determine suicide risk. All individual, household and area-based attributes were derived from census records and selected on the basis of known suicide risk. Five categories of psychotropic medication were identified; none, antidepressants, anxiolytics, hypnotics and antipsychotics. Logistic regression was used to construct models to test the association between specific types of psychotropic medication (singularly and in combinations) and death by suicide adjusting for sociodemographic and physical health characteristics. Several sensitivity analyses were conducted taking into consideration the different timing, amount/threshold of medication and changes in medications consumed.

Results About 14% of the cohort (n=153,319) had received ≥2 prescriptions of any psychotropic medication in the five months around Census. Eight hundred and seventy persons (n=870) died by suicide during 2011 to 2015. Suicide was higher in those on psychotropic medication than in those without (0.24% versus 0.05% respectively). In the fully adjusted logistic regression model, association between death by suicide and any psychotropic medication record remained statistically significant (AOR=3.69, 95%CI: 3.13–4.35). However, individuals solely on hypnotics had the highest AOR of those on singular medication (AOR=4.24, 95%CI: 2.96–6.06 compared to just AOR=2.22, 95%CI: 1.75–2.82 for those on antidepressant medication only). In terms of medication combinations, use of both anxiolytics and hypnotics (AOR=8.76, 95%CI: 5.93–12.94) and a combination of antidepressants, anxiolytics and hypnotics (AOR=8.53, 95%CI: 5.62–12.94) were the strongest predictors of deaths by suicide.

Conclusion Risk of death by suicide varied by medication type with hypnotic medications making an important contribution to death by suicide. Although previous work has focused on antidepressant therapy and suicide risk, those on hypnotic medication are an at-risk group that warrant further attention.