National study of suicide method in violent criminal offenders

BACKGROUND: Gaining a greater knowledge of the mechanisms and means by which violent offenders die by suicide can inform tailored preventive strategies. METHODS: Using interlinked national Danish registry data we constructed a nested case-control study dataset of all adult suicides during 1994-2006: N=9708 cases and N=188,134 age and gender matched living controls. Completely ascertained International Classification of Diseases 10th revision cause-specific mortality codes were examined, with all criminal charges since 1980, and covariate information on psychiatric treatment and socio-demographics. Self-poisonings were classified as 'nonviolent' suicide and all other methods as being 'violent' ones. RESULTS: Compared with the general population, risk among male and female violent offenders was strongly and significantly elevated for suicide by either a violent or a nonviolent method, although the relative risk was greater for nonviolent suicide. These patterns were also observed among nonviolent offenders, albeit with smaller effect sizes. Risk was especially raised for self-poisoning with narcotics & hallucinogens. We could only examine the full range of suicide methods in male violent offenders. In these men, hanging was the most frequently used method, although risk was markedly and significantly elevated virtually across the entire range of regularly used suicide methods. LIMITATIONS: We lacked sufficient statistical power for undertaking a detailed profiling of specific suicide methods among female violent offenders. CONCLUSIONS: Our findings indicate that comprehensive and broadly-based preventive approaches are needed for tackling the markedly raised risk of suicide by both violent and nonviolent means in this population. Their high relative risk for self-poisoning by illicit or illegal drugs underlines the importance of access to means and of prevailing subculture.