Discharge from mental health service admissions as a short-term causal risk factor for suicide: A case-crossover study

BACKGROUND: The month following discharge from inpatient mental health treatment is the period associated with the highest short-term risk of suicide. The nature of this risk is not well understood. We aim to assess a potential short term causal effect of discharge on suicide risk using a novel counterfactual framework for causal inference. METHODS: National registry linkage study with individuals 18 years or older who died by suicide from 1.1.2018 to 31.12.2022 and was discharged in the last year (N = 731). We used a Case-crossover design comparing risk at a case-time and five randomly selected control-times within subjects and employed the Mantel-Haenszel estimator. RESULTS: We found an effect of discharge on the Incidence Rate Ratio (IRR) for suicide within 14 days (IRR = 5.48 95 % CI:4.37-6.72). Comparing the first four weeks, the IRR was 6.32 (95 % CI 4.87-8.00) for the first week, with significantly reduced risk for subsequent weeks. CONCLUSION: Our findings are consistent with a causal effect of discharge on short-term suicide risk, under the assumptions described and controlling for confounders not addressed in prior studies. Recognizing this risk as causal enhances our understanding of the suicides that happen shortly after discharge and emphasizes the importance of identifying realistic targets for intervention in the post discharge period, which can then be evaluated through clinical trials.