ARCHIVED - Executive Summary for the Report on Cumulative Incidence of Post-Traumatic Stress Disorder and Other Mental Disorders

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Mental health problems (MHP's) are characterized by alterations in an individual's thoughts, mood and/or behaviour that are a source of significant distress and impaired functioning. MHP's are of interest to employers, given their impact on productivity, absenteeism, turnover, and other adverse outcomes. In military organizations, MHP's have additional significance in that:

  • MHP's can be triggered by operational stressors such as combat;
  • MHP's can interfere with the safety and success of military operations; and
  • Military organizations deliver significant amounts of mental health care.

The Canadian Forces (CF) have deployed over 40,000 individuals in support of the mission in Afghanistan since its inception in 2001; more than 150 have lost their lives, and many more have been seriously injured. For this reason, interest in long-term psychological effects of CF deployments has never been greater.

Over the past decade, the CF has renewed its mental health system and has undertaken a number of research projects intended to gauge the impact of Operational Stress Injuries1 (OSI's) on the CF and its members. Taken as a whole, these studies have shown that an important minority of previously-deployed CF members have developed OSI's. Many of these studies have important limitations in that they have largely:

  • Focused on only a subset of the deployed population;
  • Focused on data collected using questionnaires as opposed to clinical diagnoses made by a mental health professional; and
  • Reflected only brief periods of post-deployment follow-up (e.g, less than a year).

This study overcomes these limitations by estimating the fraction of a broad range of previously deployed personnel formally diagnosed with an OSI by the CF over an average of 4.5 years of follow-up.


30,518 personnel were identified to have started a deployment in support of the mission in Afghanistan on or before 31 December 2008, through linkage and cross-validation of data from the Canadian Forces Tasking, Planning, and Operations database (CFTPO), the Human Resources Management System (HRMS), and the Central Computerized Pay System (CCPS).

Data on mental health service utilization were used to improve the efficiency of the medical record review process, by identifying the subset that were potentially assessed for MHP's. Utilization data were obtained from the Canadian Forces Health Information System (CFHIS) appointment register, the Federal Health Claims Processing System (for out-sourced care), and various legacy data sources for bases that had implemented the CFHIS appointment system only recently.

A random sample of 2,045 individuals stratified by primary deployment location and the apparent use or non-use of mental health services was selected for medical record reviews. Experienced Research Nurses abstracted data on the assessment process, the diagnoses made, the clinician's attribution of the diagnoses to CF operations, and the planned treatment. 1,934 medical record reviews were completed for this interim analysis, reflecting 95% of the intended sample.


Over an average period of follow-up after return from the first deployment of 54 months, an estimated 30% of the cohort received specialty mental health services (that is, care other than Psychosocial Services or primary care) through the CF. 8% of the entire cohort was diagnosed with Afghanistan-related PTSD (with or without other disorders), and an additional 5.2% were diagnosed with other Afghanistan-related OSI's, such as depression (2.2%), adjustment disorders (2.0%), or anxiety disorders other than PTSD (1.9%). Non-OSI mental disorders and OSI's related to other operations were less common in this cohort (affecting 4.5% and 1.2%, respectively).

The fraction of a cohort diagnosed with a given condition at any point over a specified period of follow-up is termed the “cumulative incidence” of the condition. The cumulative incidence of OSI's was highest for those deployed to Kandahar (17.1%) and to Kabul (14.5%) and was lower for those deployed to the Arabian Gulf (6.5%) and to Camp Mirage or elsewhere in SW Asia (3.3%). However, even lower-threat locations such as Camp Mirage had meaningful rates of OSI's.


13.2% of a large, diverse cohort of CF personnel who deployed in support of the mission in Afghanistan were diagnosed with an Operational Stress Injury over an average period of follow-up of almost five years. PTSD was the most common disorder (seen in 8% of the cohort), but 5.2% had one or more OSI's other than PTSD. A sizable fraction of all mental health disorders diagnosed in the previously-deployed cohort were judged to be OSI's.

Once methodological differences (particularly the duration of the follow-up period) are considered, the cumulative incidence for Afghanistan-related OSI's (13.2%) is consistent with other studies on the mental health impact of the mission, such as the frequently-reported findings from the Enhanced Post-deployment Screening Process. Unfortunately, there is no methodologically-similar international comparison data, so it is unknown whether this rate is higher or lower than those of our allies.

This study has significant strengths relative to previous CF studies and studies done in other countries:

  • It reflects a broad range of operational experience since the beginning of the mission;
  • It uses clinical diagnoses rather than questionnaire results to estimate the impact of the operation; and
  • It uses a prolonged follow-up period.

The main limitation of the study is that it could not capture the diagnoses of those who did not seek care through the CF or those who will develop problems in the future. Nevertheless, delayed onset of OSI's is believed to be relatively uncommon, and the study did have a relatively long follow-up period.

In addition, no diagnostic process is 100% reliable, and attribution of a disorder to a deployment can be difficult. Nevertheless, the CF's mental health assessments are unusually thorough, and the CF arguably has more experience than any other large institution in Canada in the diagnosis and treatment of traumatic stress disorders. For these reasons, systematic diagnostic and attribution errors seem unlikely.

The main implication of this study to the CF is that it needs to be prepared to deliver high quality mental health care to the important minority of previously deployed personnel who will inevitably develop an OSI in response to a demanding operation. Further analysis of the data collected during this study will address additional issues, including a formal survival analysis and determination of long-term organizational outcomes in those with OSI's.

1 The CF refers to any persistent psychosocial problem that occurs as a result of a military operation as an “Operational Stress Injury” (OSI)

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