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We are writing to you in response to Mahar et al.’s (2019) recent publication in your journal (“Suicide in Canadian veterans living in Ontario: a retrospective cohort study linking routinely collected data”).
The authors found a lower risk of suicide in Canadian Armed Forces (CAF) Veterans (former members) using Ontario Health Insurance Plan coverage, in contrast to the findings of higher CAF Veteran suicide risk in the Canadian Forces Cancer and Mortality Study (CF CAMS) and the Veteran Suicide Mortality Study (VSMS), which use nation-wide Vital Statistics and cancer registry data collected by Statistics Canada. We strongly feel that there is synergistic value in having different studies by different investigator groups using different data sources, but it is essential to understand the limitations in these different approaches and their findings.
Mahar et al. state that their study was the “...first study of suicide risk in Canadian veterans...” However, CF CAMS, which looked at suicide risk in Canadian Veterans, was published eight years prior to the Mahar et al. study (Statistics Canada, 2011). This was followed by the Veteran Suicide Mortality Study (VSMS) Technical report was published in 2017 (Simkus et al., 2017), its accompanying peer-reviewed publication (VanTil et al., 2018), and the 2018 VSMS Technical report (Simkus et al., 2018).
We have questions about the authors’ choice of covariates for the adjusted an...
We have questions about the authors’ choice of covariates for the adjusted analysis. Specifically, the authors did not adjust for mental illnesses because they asserted that mental illnesses are on the causal pathway to suicide. However, most with mental illness do not die by suicide (Nordentoft et al., 2013). A diagnosis of depression is common in those who die by suicide but remains a poor predictor of a suicidal act (Franklin et al., 2017). Furthermore, the authors’ use of socioeconomic factors and physical health problems as covariates implies that they felt that those factors are not on the suicide causal pathway. This is counter to the epidemiological, clinical and theoretical evidence indicating that such factors are on causal pathways to suicide (Gunnell and Lewis, 2005). The authors wrote that they chose as covariates “established risk factors”, but Franklin et al. (2017) demonstrated that epidemiologists have tended to look at a narrow list of risk indicators over the past 50 years. Just because researchers keep using the same risk indicators does not mean that those indicators are “established” as significant.
We think that Mahar et al.’s statements of discordance between their findings and the CFCAMS findings are overstated, particularly given the lack of statistical significance to support their assertions. The breadth of the confidence intervals in their adjusted models suggest that their findings may actually be aligned with the findings published in studies with census-level coverage of the Veteran population (namely the CF CAMS study [Statistics Canada, 2011] and the VSMS publications [Simkus et al, 2017; Simkus et al, 2018; Van Til et al, 2018]) that found the risk of suicide to be significantly elevated in those with a history of military service. However, a notable exception was the youngest male age group, where the OHIP study reports much lower rates than VSMS. Unfortunately, the authors did not discuss the effect of the OHIP “under-representation of those who released before age 25” on their subsequent comparisons of Veteran and civilian suicides. Future examination of Veterans in the OHIP data should be more cautious in extrapolating conclusions to all Veterans, particularly for conditions that are more common in younger Veterans.
Disagreements notwithstanding, we agree wholeheartedly with the authors’ statement that “...this work raises a need to conduct further high-quality research on the topic of suicide in the military, including veteran populations”, as recommended in the Canadian Armed Forces – Veterans Affairs Canada Joint Suicide Prevention Strategy (CAF and VAC, 2017).
Canadian Armed Forces, Veterans Affairs Canada. Joint Suicide Prevention Strategy. Ottawa, ON: Canadian Armed Forces and Veterans Affairs Canada. 2017.
Franklin JC, Ribeiro JD, Fox KR, Bentley KH, Kleiman EM, Huang X, Musacchio KM, Jaroszewski AC, Chang BP, Nock MK. Risk factors for suicidal thoughts and behaviors: a meta-analysis of 50 years of research. Psychological Bulletin. 2017;143(2):187.
Gunnell D, Lewis G. Studying suicide from the life course perspective: implications for prevention. British Journal of Psychiatry. 2005;187:206-8.
Mahar AL, Aiken AB, Whitehead M, Tien H, Cramm H, Fear NT, Kurdyak P. Suicide in Canadian veterans living in Ontario: A retrospective cohort study linking routinely collected data. BMJ Open. 2019;9:e027343.
Nordentoft M, Wahlbeck K, Hällgren J, Westman J, Ösby U, Alinaghizadeh H, Gissler M, Laursen TM. Excess mortality, causes of death and life expectancy in 270,770 patients with recent onset of mental disorders in Denmark, Finland and Sweden. PloSOne. 2013;8(1):e55176.
Simkus K, VanTil LD, Pedlar D. 2017 Veteran Suicide Mortality Study (1976 to 2012). Charlottetown, PEI (Canada): Veterans Affairs Canada, 2017.
Simkus K, VanTil LD. 2018 Veteran Suicide Mortality Study: Identifying risk groups at release. Charlottetown, PEI (Canada): Veterans Affairs Canada, 2018.
Statistics Canada. Canadian Forces Cancer and Mortality Study: Causes of death. Catalogue no. 82-584-X. Ottawa (Canada): Minister for Industry, 2011.
VanTil L, Simkus K, Rolland-Harris E, Pedlar DJ. Veteran suicide mortality in Canada from 1976 to 2012. Journal of Military, Veteran, and Family Health. 2018;4(2):110-6.