Background People with a severe mental illness (SMI) die earlier compared to the general population. This gap in life expectancy (LE) is reported to be widening in some settings. We estimated the LE gap for people with a SMI in Scotland between 2000 and 2019 and determined whether the gap has changed over time.

Methods We conducted a population-based study, comparing excess life years lost for adults with SMI (schizophrenia; bipolar disorder [BD]; and depression) compared to the general Scottish population, from 2000 to 2019. We ascertained SMI diagnosis from psychiatric hospital admission International Classification of Diseases (ICD) version 10 codes. The SMI cohort included 117,958 people alive on 1 January 2000 with a SMI diagnosis recorded between 1981 and 2019. We identified deaths through linkage to National Records of Scotland (NRS) data, using ICD-10 codes to identify natural and unnatural causes of death. To estimate years of life lost in each SMI group and by type of death and sex, we applied the Life Years Lost (LYL) method, which accounts for variation in age of onset of SMI. To assess time-trends we calculated LYL for 18 three-year rolling averages, to align with reporting of general population LE data by NRS.

Results Within the SMI cohort, 28,797 had schizophrenia, 16,657 had BD and 72,504 had depression, and 34% died during the study period. Compared with the general population, people with each SMI had lower LE during each three-year period. Based on data for 2017-2019, compared to the general population, LE was approximately 11 years lower in people with schizophrenia and 7 years lower in people with BD or depression. In the general Scottish population, LE increased between 2000 and 2019. During this time, the LE gap remained stable for people with BD or depression. In 2000-2002, compared to the general population, men and women with schizophrenia lost 9.4 (95% CI 8.5, 10.3) and 8.2 (7.4, 9.0) life years, respectively. In 2017-2019, this increased to 11.8 (10.9, 12.7) and 11.1 (10.0, 12.1) LYL for men and women, respectively. YLL and their changes in LE for natural and unnatural causes of death varied by individual SMI and sex.

Conclusion The large gap in LE of people with an SMI persisted or widened in Scotland from 2000-2019. These findings highlight the entrenched lower LE experienced by this vulnerable sub-population and the need for renewed efforts to address these persistent disparities.