Combined influence of serious mental illness and criminal offending on suicide risk in young adults.

Purpose: We conducted a national epidemiological study to determine how mental illness and criminal offending combine to influence suicide risk in younger adults. Methods: Using completely interlinked registers, we generated a nested case-control study from the cohort of all Danish people born 1965 and onwards. We identified 2,384 suicides aged 15-41 years during 1981-2006, and 56,016 age and sex-matched living controls. We examined all criminal charges from 1980, and all psychiatric admissions from 1969 and outpatient episodes from 1995. Exposure odds ratios were estimated using conditional logistic regression models. Results: A quarter of male and 17 % of female suicides had histories of both criminal justice system contact and secondary care psychiatric treatment, with a marked elevation in risk seen compared with having neither risk factor: male odds ratio (OR) 34.0, 95 % confidence interval (CI) 29.1-39.6; female OR 72.7, CI 49.4-107.1. Among those treated for psychiatric illness, contact with the criminal justice system predicted higher risk: male OR 1.4, CI 1.1-1.7; female OR 1.7, CI 1.1-2.4, although these effects were attenuated and became non-significant with adjustment for socio-demographic risk factors. In men, risk was especially high if first criminal justice system contact occurred before first psychiatric treatment episode, and if these two challenging life events coalesced within a year of each other. Conclusion: These younger age adults should be monitored carefully for signs of suicidal behaviour. The need for well coordinated multiagency care is indicated, and a broad range of psychiatric illnesses should be considered carefully when assessing their suicide risk.