Deployment-related mental disorders among Canadian Forces personnel deployed in support of the mission in Afghanistan, 2001-2008

Background: The conflict in Afghanistan has exposed more Canadian Forces personnel to a greater degree of adversity than at any time in recent memory. We determined the incidence of Afghanistan deployment-related mental disorders and associated risk factors among personnel previously deployed in support of this mission. Methods: The study population consisted of 30 513 Canadian Forces personnel who began a deployment in support of the mission in Afghanistan before Jan. 1, 2009. The primary outcome was a mental disorder perceived by a Canadian Forces clinician to be related to the Afghanistan deployment. Data on diagnoses and perceptions were abstracted from medical records of a stratified random sample of 2014 personnel. Sample design weights were used in all analyses to generate descriptive statistics for the entire study population. Results: Over a median follow-up of 1364 days, 13.5% (95% confidence interval [CI] 12.1%-14.8%) of the study population had a mental disorder that was attributed to the Afghanistan deployment. Posttraumatic stress disorder was the most common diagnosis (in 8.0%, 95% CI 7.0%-9.0%, of personnel). Deployment to higher-threat locations, service in the Canadian Army and lower rank were independent risk factors associated with an Afghanistan-related diagnosis (e.g., hazard ratio for deployment to Kandahar Province 5.6, 95% CI 2.6-12.5, relative to deployment to the United Arab Emirates). In contrast, sex, Reserve Forces status, multiple deployments and deployment length were not independent risk factors. Interpretation: An important minority of Canadian Forces personnel deployed in support of the Afghanistan mission had a diagnosis of a mental disorder perceived to be related to the deployment. Determining long-term outcomes is an important next step.