Excess mortality among adults with mental disorders treated in psychiatric and general medical settings: A population-based cohort study using municipal medical claims data in Japan.

OBJECTIVES

To estimate the excess mortality associated with serious mental illnesses (schizophrenia and bipolar disorder) and common mental disorders (depression and anxiety) at the population level.

METHODS

We conducted a population-based, retrospective cohort study in Tsukuba, Japan. Individuals aged 20-74 years and insured for at least 12 months by the National Health Insurance or Late Elders' Health Insurance as of April 2015 were included (n = 41,618, 29% of the city's population aged 20-74 years). Individuals with mental disorders (International Classification of Diseases-10 code: F00-F99) were identified in psychiatric and general medical services using medical claims during the 12-month baseline period and classified into mutually exclusive diagnostic subgroups. Their age/sex-adjusted all-cause mortality rate ratios (aMRRs) were estimated and compared to those of individuals without mental disorders.

RESULTS

Altogether, 12.0% of participants had mental disorders (general medical service: 7.2% vs. psychiatric service: 4.8%). Common mental disorders were the most prevalent (8.1%). During the median 48 months of observation, 225 deaths were observed in people with mental disorders. The aMRR was 1.98 (95%CI: 1.70-2.29) for all mental disorders, with a higher rate ratio in psychiatric service than in general medical service users (aMRR: 2.64 [2.12-3.29] vs. 1.70 [1.42-2.04]), 3.57 (2.71-4.70) for serious mental illness, with a higher rate ratio in psychiatric inpatient service than in outpatient service users (aMRR: 5.74 [3.76-8.78] vs. 2.84 [2.00-4.04]), and 1.53 (1.27-1.84) for common mental disorders.

CONCLUSION

Serious and common mental disorders in psychiatric and general health services are associated with increased mortality in Japan.