Severe depression and all-cause and cause-specific mortality in Scotland: 20 year national cohort study

Background Understanding cause of death in people with depression could inform approaches to reducing premature mortality. Aim To describe all-cause and cause-specific mortality for people with severe depression in Scotland, by sex, relative to the general population.MethodWe performed a retrospective cohort study, using psychiatric hospital admission data linked to death data, to identify adults (>= 18 years old) with severe depression and ascertain cause-specific deaths, during 2000-2019. We estimated relative all-cause and cause-specific mortality for people with severe depression using standardised mortality ratios (SMRs), stratified by sex using the whole Scottish population as the standard. Results Of 28 808 people with severe depression, 7903 (27.4%) died during a median follow-up of 8.7 years. All-cause relative mortality was over three times higher than expected (SMR, both sexes combined: 3.26, 95% CI 3.19-3.34). Circulatory disease was the leading cause of death, and, among natural causes of death, excess relative mortality was highest for circulatory diseases (SMR 2.51, 2.40-2.66), respiratory diseases (SMR 3.79, 3.56-4.01) and 'other' causes (SMR 4.10, 3.89-4.30). Among circulatory disease subtypes, excess death was highest for cerebrovascular disease. Both males and females with severe depression had higher all-cause and cause-specific mortality than the general population. Suicide had the highest SMR among both males (SMR 12.44, 95% CI 11.33-13.54) and females (22.86, 95% CI 20.35-25.36). Conclusion People with severe depression have markedly higher all-cause mortality than the general population in Scotland, with relative mortality varying by cause of death. Effective interventions are needed to reduce premature mortality for people with severe depression.