Death by homicide, suicide, and other unnatural causes in people with mental illness: a population-based study

Abstract

Background: People with mental illness are at great risk of suicide, but little is known about their risk of death from other unnatural causes. No study has commented on their risk of being victims of homicide; public concern is pre-occupied with their role as perpetrators. We aimed to calculate standardised mortality ratios (SMRs) and directly standardised rate ratios for death by homicide, suicide, and accident in people admitted to hospital because of mental illness.

Method: We did a population-based study in which we linked the data for 72208 individuals listed in the Danish Psychiatric Case Register between 1973 and 1993, and who died before Dec 31, 1993, with data in the Danish National Register of Causes of Death.

Findings: 17892 (25%) patients died from unnatural causes. Our results show raised SMRs for homicide, suicide, and accident for most psychiatric diagnoses irrespective of sex. The all-diagnosis SMRs for women and men, respectively, were: 632 (95% CI 517-773) and 609 (493-753) for homicide, 1356 (1322-1391) and 1212 (1184-1241) for suicide, and 318 (305-332) and 466 (448-484) for accident. We recorded an increased risk of dying by homicide in men with schizophrenia and in individuals with affective psychosis. The highest risks of death by homicide and accident were in alcoholism and drug use, whereas the highest risks of suicide were in drug use.

Interpretation: People with mental disorders, including severe mental illness, are at increased risk of death by homicide. Strategies to reduce mortality in the mentally ill are correct to emphasise the high risk of suicide, but they should also focus on other unnatural causes of death.