Mental disorder and long-term risk of mortality: 41 years of follow-up of a population sample in Stockholm, Sweden.

BACKGROUND: An increased mortality risk associated with mental disorder has been reported for patients, but there are few studies are based on random samples with interview-based psychiatric diagnoses. Part of the increased mortality for those with mental disorder may be attributable to worse somatic health or hazardous health behaviour - consequences of the disorder - but somatic health information is commonly lacking in psychiatric samples. This study aims to examine long-term mortality risk for psychiatric diagnoses in a general population sample and to assess mediation by somatic ill health and hazardous health behaviour.
METHOD: We used a double-phase stratified random sample of individuals aged 18-65 in Stockholm County 1970-1971 linked to vital records. First phase sample was 32 186 individuals screened with postal questionnaire and second phase was 1896 individuals (920 men and 976 women) that participated in a full-day examination (participation rate 88%). Baseline examination included both a semi-structured interview with a psychiatrist, with mental disorders set according to the 8th version of the International Classification of Disease (ICD-8), and clinical somatic examination, including measures of body composition (BMI), hypertension, fasting blood glucose, pulmonary function and self-reported tobacco smoking. Information on vital status was obtained from the Total Population Register for the years 1970-2011. Associations with mortality were studied with Cox proportional hazard analyses.
RESULTS: A total of 883 deaths occurred among the participants during the 41-year follow-up. Increased mortality rates were found for ICD-8 functional psychoses (hazard ratio, HR = 2.22, 95% confidence interval (95% CI): 1.15-4.30); psycho-organic symptoms (HR = 1.94, 95% CI: 1.31-2.87); depressive neuroses (HR = 1.71, 95% CI: 1.23-2.39); alcohol use disorder (HR = 1.91, 95% CI: 1.40-2.61); drug dependence (HR = 3.71, 95% CI: 1.80-7.65) and psychopathy (HR = 2.88, 95% CI: 1.02-8.16). Non-participants (n = 349) had mortality rates similar to participants (HR = 0.98, 95% CI: 0.81-1.18). In subgroup analyses of those with psychoses, depression or alcohol use disorder, adjusting for the potential mediators smoking and pulmonary function, showed only slight changes in the HRs.
CONCLUSIONS: This study confirms the increased risk of mortality for several psychiatric diagnoses in follow-up studies on American, Finnish and Swedish population-based samples. Only a small part of the increased mortality hazard was attributable to differences in somatic health or hazardous health behaviour measured at baseline.