Heterogeneity in Excess Mortality Across Mental, Behavioural, and Neurodevelopmental Disorders

Importance: Excess mortality associated with mental disorders is well established, but estimates are largely based on specialist psychiatric populations. Whether they characterize mortality in the broader diagnosed population is uncertain. Objective: To characterize heterogeneity in excess mortality by diagnosis, psychiatric care setting, substance use disorder (SUD), and time since diagnosis. Design: Nationwide population-based cohort study with follow-up from January 1, 2011, through December 31, 2023. Setting: Primary and specialist health care and population registers in Finland. Participants: Residents aged 5 to 95 years without a recorded prevalent mental disorder at cohort entry. Exposures: Mental, behavioural, and neurodevelopmental disorders classified using ICD-11, with time-varying psychiatric care setting and SUD status. Main Outcomes and Measures: All-cause mortality, mortality rate ratios (MRRs), and 10-year differences in restricted mean survival time (RMST). Results: Among 5,526,599 individuals (2,784,897 [50.4%] women), 1,463,064 (26.5%) received a mental disorder diagnosis. Excess mortality varied substantially by diagnosis, clinical subgroup, and time since diagnosis. Among those aged 5 to 64 years with any mental disorder, adjusted MRRs across care setting and SUD strata ranged from 1.54 (95% CI, 1.39-1.71) to 8.97 (7.86-10.24). MRRs were highest immediately after first diagnosis and declined during the first 2 to 3 years. At 3 years, MRRs for depressive, anxiety or fear-related, and stress-related disorders among individuals without SUD treated outside specialist psychiatric care ranged from 0.88 (0.79-0.98) to 1.20 (1.12-1.29) in men and from 0.81 (0.73-0.89) to 1.13 (1.04-1.22) in women, whereas MRRs for schizophrenia and other primary psychotic disorders remained 1.84 (1.60-2.12) in men and 1.55 (1.37-1.75) in women. Ten-year survival loss across all mental disorders was 0.53 years (95% CI, 0.53-0.54) in men and 0.34 years (0.33-0.34) in women and was greater for natural than external causes. Conclusions and Relevance: Excess mortality varied markedly by diagnosis, clinical context, and time since diagnosis and was small in some common disorders outside specialist psychiatric care without SUD. Estimates derived from specialist psychiatric populations or averaged across follow-up may therefore provide an incomplete picture of mortality in the broader diagnosed population.