Epidemiological studies of suicide in patients with psychiatric illness

Sammanfattning: A link between suicide and psychiatric illness is well recognized. However, knowledge is limited as to what characterizes suicide in different mental disorders. The overall aim of the work described in this thesis was to increase the understanding of suicide in psychiatric illness. Study I: In this population-based case-control study, all suicide cases 18 years and older in Sweden from 1991 to 2003 (14,501 men and 6,174 women) were individually matched to ten controls from the general population. Of male and female suicide victims, 23% and 31%, respectively, had been hospitalized with a mental disorder in the year before the suicide. The highest suicide risk during hospitalization and in the year following discharge was found in patients with mood disorder [odds ratio (OR) 55 (95% CI 47–65) for men and OR 86 (95% CI 70–107) for women] with the risk peaking in the first week following discharge [OR 177 (95% CI 78–401) for men and OR 268 (95% CI 85–846) for women]. Compared to that for mood disorder, the suicide risks for schizophrenia spectrum disorder and alcohol use disorder were about half and were more constant over time. Study II: Seasonal patterns among suicides committed by individuals aged 18 years and older in Sweden from 1992 to 2003 (9,902 men and 4,128 women) were assessed in relation to their history of psychiatric inpatient diagnosis in the five years before the suicide. We found an increased incidence of suicide in spring and early summer. The seasonal variation was more evident in suicide victims with a psychiatric illness than in those without such a diagnosis. The seasonal variation was found in most of the eight diagnostic groups studied. Studies III and IV: These population-based case-control studies focused on suicide among patients diagnosed with schizophrenia in Stockholm County from 1984 to 2000. Data from 84 patients who died by suicide within five years from the diagnosis were compared with 84 matched controls from the same study population. We found that higher educational attainment, age ≥30 years at onset of symptoms, and a history of a suicide attempt were associated with an increased risk of suicide. Gender did not significantly affect the suicide risk, nor did substance use disorder or a family history of mental disorder or suicide. A diagnostic re-assessment according to DSM-IV criteria of the cases and controls showed that a mood disorder diagnosis increased the risk of suicide more than three-fold. We conclude that certain risk factors for suicide in schizophrenia may differ from those found in the general population and other mental disorders. The identification of mood disorder is important for suicide risk assessment in patients with schizophrenia.