Contribution of traumatic deployment experiences to the burden of mental health problems in Canadian Armed Forces personnel: exploration of population attributable fractions

Purpose Mental health problems are prevalent after combat; they are also common in its absence. Estimates of deployment-attributability vary. This paper quantifies the contribution of different subtypes of occupational trauma to post-deployment mental health problems. Methods Participants were a cohort of 16,193 Canadian personnel undergoing post-deployment mental health screening after return from the mission in Afghanistan. The screening questionnaire assessed post-traumatic stress disorder, depression, panic disorder, generalized anxiety disorder, and exposure to 30 potentially traumatic deployment experiences. Logistic regression estimated adjusted population attributable fractions (PAFs) for deployment-related trauma, which was treated as count variables divided into several subtypes of experiences based on earlier factor analytic work. Results The overall PAF for overall deployment-related trauma exposure was 57.5% (95% confidence interval 44.1, 67.7) for the aggregate outcome of any of the four assessed problems. Substantial PAFs were seen even at lower levels of exposure. Among subtypes of trauma, exposure to a dangerous environment (e.g., receiving small arms fire) and to the dead and injured (e.g., handling or uncovering human remains) had the largest PAFs. Active combat (e.g., calling in fire on the enemy) did not have a significant PAF. Conclusions Military deployments involving exposure to a dangerous environment or to the dead or injured will have substantial impacts on mental health in military personnel and others exposed to similar occupational trauma. Potential explanations for divergent findings in the literature on the extent to which deployment-related trauma contributes to the burden of mental disorders are discussed.