The impact of psychiatric illness on suicide: differences by diagnosis of disorders and by sex and age of subjects.

People with a psychiatric illness are at high risk for suicide; however, variation of the risk by patients' sex and age and by specific diagnosis needs to be explored in a more detail. This large population study systematically assesses suicide incidence rate ratio (IRR) and population attributable risk (PAR) associated with various psychiatric disorders by comparing 21,169 suicides in Denmark over a 17-year period with sex-age-time-matched population controls. The study shows that suicide risk is significantly increased for persons with a hospitalized psychiatric disorder and the associated risk varies significantly by diagnosis and by sex and age of subjects. Further adjustment for personal socioeconomic differences eliminates the IRRs associated with various disorders only to a limited extend. Recurrent depression and borderline personality disorder increase suicide risk the strongest while dementia increases the risk the least for both males and females. The influence of various disorders generally weakens with increasing age; however, there are important exceptions. Schizophrenia affects people aged ≤35 years the strongest in terms of both IRR and PAR. Recurrent depression increases suicide risk particularly strong in all age groups and the associated PAR increases steadily with age. Borderline personality disorder has a strong effect in young people, especially those ≤35 years. Alcohol use disorder accounts the highest PAR of suicides in males of 36-60 years old. For the elderly above 60 years old, reaction to stress and adjustment disorder increases the risk for suicide the most in both sexes. These findings suggest that approaches to psychiatric suicide prevention should be varied according to diagnosis and sex and age of subjects.