Exposure to combat and traumatic events increases risk of violent offending among military personnel.

ED FROM MacManus D, Dean K, Jones M, et al. Violent offending by UK military personnel deployed to Iraq and Afghanistan: a data linkage cohort study. Lancet 2013;381:907–17. Correspondence to: Dr Deidre MacManus, Department of Forensic and Neurodevelopmental Sciences, Kings College London, Institute of Psychiatry, P 23, De Crespigny Park, London SE5 8AE, UK; [email protected] Sources of funding: UK Medical Research Council; UK Ministry of Defence. OM M EN TRY This study by MacManus and colleagues examining the relationship between combat deployment and subsequent aggressive behaviour makes an excellent contribution to the literature on violence. The study design has many positive features of which the following are the most significant. First, it controls for levels of predeployment and pre-existing violence. Second, the research project permits an examination of deployment effects separately from combat role and trauma exposure. Third, it provides reliable data on aggression rates using police national computer (PNC) records rather than relying exclusively on self-report. While the study’s findings cohere well with existing research, the methodological improvements noted above make the results more robust. The clinical implications of the present study are noteworthy. The authors’ conclusion that increased rates of aggression after military deployment is related to combat exposure and the presence of mental health problems is therapeutically important. Of particular interest is the discovery that alcohol abuse and post-traumatic stress disorder (PTSD) hyperarousal are predictive of postdeployment violence. Furthermore, the fact that self-reported aggression is correlated with official records is encouraging, as clinicians often only have access to this type of data. Despite the strengths above, there are some research problems pinpointed by this paper that merit further exploration. While the study demonstrates important links between symptoms and contexts, its design does not allow us to make inferences about the underlying psychological mechanisms. Soldiers ingest substances for all sorts of reasons, not necessarily because of the trauma they might have experienced. The causal directions between alcohol abuse, PTSD, other mental health problems and combat-related norms, could be complex and variable. For example, the culture of combat soldiers might encourage excessive drinking or the taking of unnecessary risks that result in increased risk of trauma. Another possibility is that the comparative lack of structure after leaving the military could act as a facilitator of violence in individuals who are struggling with mental health and alcohol problems; perhaps related to combat and trauma. This study lays down a strong conceptual and empirical foundation for future investigation of these complex issues.