Risk of Suicide Across Medical Conditions and the Role of Prior Mental Disorder

IMPORTANCE: According to the World Health Organization, more than 700 000 individuals worldwide die by suicide each year. Medical conditions likely increase the risk of suicide. OBJECTIVE: To (1) provide age- and sex-specific pairwise estimates of the risk of suicide across a comprehensive range of medical conditions, (2) investigate whether there is a dose-response-like relationship at play (ie, the higher the disability burden due to medical morbidity, the higher the risk of suicide), and (3) determine if the risk of suicide with medical conditions is particularly pronounced among those who had mental disorder preceding the medical conditions. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was an observational study of population-based data for all individuals living in Denmark at some point between 2000 and 2020. The data analysis took place from September 2023 to May 2024. EXPOSURES: Thirty-one specific medical conditions as well as prior mental disorder. MAIN OUTCOMES AND MEASURES: The main outcome was suicide. Associations between the 31 specific medical conditions, nested within 9 categories, and suicide were examined via Poisson regression, yielding incidence rate ratios (IRRs). Subsequent analyses included an interaction term to assess whether a previous hospital-treated mental disorder modified the associations. Finally, the association between the disability burden of medical conditions and suicide was examined for those with and without prior mental disorder, respectively. RESULTS: A total of 6 635 857 individuals (3 337 613 females and 3 298 244 males) were included in the analyses of the associations between medical conditions and suicide. Except for endocrine disorders, all categories of medical conditions were associated with a statistically significant increased risk of suicide (which was most pronounced for gastrointestinal conditions IRR, 1.7; 95% CI,1.5-1.8, cancer IRR, 1.5; 95% CI, 1.4-1.6, and hematological conditions IRR, 1.5; 95% CI, 1.3-1.6). Interaction between mental disorder and individual medical conditions did not seem to play a major role for suicide risk. For those without but not for those with mental disorder, there was a dose-response-like relationship between the disability burden of medical conditions and suicide. CONCLUSIONS AND RELEVANCE: Medical conditions are generally associated with increased risk of suicide in a dose-response-like manner. Individuals with hospital-treated mental disorder appear to be at such elevated risk of suicide that additional disability associated with medical conditions has little impact in this regard.