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Research

Mental disorders and vulnerability to homicidal death: Swedish nationwide cohort study

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f557 (Published 05 March 2013) Cite this as: BMJ 2013;346:f557
  1. Casey Crump, clinical assistant professor1,
  2. Kristina Sundquist, professor2,
  3. Marilyn A Winkleby, professor3,
  4. Jan Sundquist, professor and director2
  1. 1Department of Medicine, Stanford University, 211 Quarry Road, Suite 405, MC 5985, Palo Alto, CA 94304-1426, USA
  2. 2Center for Primary Health Care Research, Lund University, Skåne University Hospital, Malmö, Sweden
  3. 3Stanford Prevention Research Center, Stanford University, Stanford, CA 94305-5411, USA
  1. Correspondence to: C Crump kccrump{at}stanford.edu
  • Accepted 8 January 2013

Abstract

Objective To determine the risk of people with mental disorders being victims of homicide.

Design National cohort study.

Setting Sweden.

Participants Entire adult population (n=7 253 516).

Main outcome measures Homicidal death during eight years of follow-up (2001-08); hazard ratios for the association between mental disorders and homicidal death, with adjustment for sociodemographic confounders; potential modifying effect of comorbid substance use.

Results 615 homicidal deaths occurred in 54.4 million person years of follow-up. Mortality rates due to homicide (per 100 000 person years) were 2.8 among people with mental disorders compared with 1.1 in the general population. After adjustment for sociodemographic confounders, any mental disorder was associated with a 4.9-fold (95% confidence interval 4.0 to 6.0) risk of homicidal death, relative to people without mental disorders. Strong associations were found irrespective of age, sex, or other sociodemographic characteristics. Although the risk of homicidal death was highest among people with substance use disorders (approximately ninefold), the risk was also increased among those with personality disorders (3.2-fold), depression (2.6-fold), anxiety disorders (2.2-fold), or schizophrenia (1.8-fold) and did not seem to be explained by comorbid substance use. Sociodemographic risk factors included male sex, being unmarried, and low socioeconomic status.

Conclusions In this large cohort study, people with mental disorders, including those with substance use disorders, personality disorders, depression, anxiety disorders, or schizophrenia, had greatly increased risks of homicidal death. Interventions to reduce violent death among people with mental disorders should tackle victimisation and homicidal death in addition to suicide and accidents, which share common risk factors.

Footnotes

  • Contributors: CC, KS, MAW, and JS were responsible for the study concept and design. JS obtained funding. KS and JS acquired the data. CC, KS, MAW, and JS analysed and interpreted the data. CC and JS did the statistical analysis. CC drafted the manuscript, and all authors revised it for important intellectual content. JS is the guarantor.

  • Funding: This study was supported by grants from the National Institute of Drug Abuse (R01DA030005), the Swedish Research Council, and ALF project grant, Lund, Sweden. The funding agencies had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript. The researchers were independent of the funding agencies.

  • Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: support for the study by grants from the National Institute of Drug Abuse (R01DA030005), the Swedish Research Council, and ALF project grant, Lund, Sweden; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the Regional Ethical Review Board of Lund University in Sweden.

  • Data sharing: No additional data available.

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