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. METHOD: We 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.