Illness-induced post-traumatic stress disorder among Canadian Armed Forces Members and Veterans

There is growing recognition of illness-induced post-traumatic stress disorder (PTSD), defined by illness being the index trauma that induces PTSD symptoms. This is the first study to examine 1) the lifetime prevalence of illness-induced PTSD among military personnel and veterans, and its 2) sociodemographic, military, trauma, and physical health condition correlates.

Participants completed the 2002 Canadian Community Health Survey-Mental Health and Well-being - Canadian Forces (N = 5155) and the 2018 Canadian Armed Forces Members and Veterans Mental Health Survey follow-up (n = 2941). A semi-structured clinical interview assessed PTSD, which we categorized as "illness-induced" or "other trauma-induced" PTSD based on the index trauma in those participating in both timepoints. To ensure representativeness of our study sample, we used baseline weights created by Statistics Canada to report weighted prevalence estimates and inferential statistics.

The estimated lifetime prevalence of PTSD among the full sample was 22% and 1.5% had lifetime illness-induced PTSD. Among those with lifetime PTSD, the proportion of participants with illness-induced PTSD was 8.3% (91.7% met criteria for other trauma-induced PTSD). In an unadjusted model, the prevalence of illness-induced PTSD was greater for females (13.7%) than males (7.2%), and for those who were not deployed in both 2002 (5.7%) and 2018 (7.1%; unadjusted odds ratio (OR) range: 2.05-3.72). In a multinomial model adjusting for sociodemographic and military characteristics, compared to those with other trauma-induced PTSD, those with illness-induced PTSD had elevated rates of PTSD persistence (24.1% vs. 11.9%; RRR = 6.06, 95% CI [1.21-30.25]) and lower rates of remission (7.8% vs. 19.9%).

Results highlight differences between illness-induced PTSD and other trauma-induced PTSD, primarily the potential chronicity of this manifestation. This may have implications for assessment strategies and targeted interventions.