Who stands most at risk of PTSD? A new study of PTSD in US veterans of the current Iraq and Afghanistan wars suggests that you can identify the most vulnerable — soldiers who stand 2 to 3 times the risk of their peers — with fairly simple measures of mental and physical health.
The study, conducted by the U.S. Navy’s Tyler Smith and collegues, is part of an ongoing longitudinal study of over 150,000 U.S. soldiers. The Millennium Cohort Study began collected comprehensive health data on U.S. soldiers in 2001. This study draws on that data to compare health status before deployment to Iraq and Afghanistan with rates of PTSD afterwards. It found that soldiers who scored in the bottom 15% of all soldiers before deployment were two to three times as likely to develop PTSD later. Those who scored in the bottom 15% in mental health stood 3 times the risk; those in the bottom 15% physically were at twice the risk. And those who scored in the bottom 15% in both mental and physical health scores got PTSD at over three times the rate of other combat deployers — 26%, as opposed to just over 7% for the study cohort as a whole.
Altogether, those who scored in the bottom 15% of either of these measures accounted for half of all PTSD diagnoses post-deployment. This is of more than just academic interest, as it suggests that more vulnerable soldiers would be identified beforehand with fairly straightforward measure — and then either kept out of the conflict and/or given extra interventions before and during the conflict that might reduce the risk. Simply keeping them home might be pretty good idea: If they’re accounting for half all cases, then simply keeping them out of war zones would cut the PTSD rate by half.
This study also firms up the rather jiggly body of research on what factors create risk for PTSD. As the Smith paper notes, most prior studies of risk for PTSD were retrospective — that is, done after soldiers or others who’d experienced stressful situations had already developed PTSD. And the few prospective or longitudinal studies so far have been tied mainly to specific measures, like high levels of anxiety or depression in first grade, that might or might not be at hand in other situations.
This new Smith study follows an early 2008 paper, drawn on the same vast pool of data, that produced one of the best studies of PTSD rates in the OIF/OEF conflicts. That study — which, as I described in my Scientific American article on PTSD, went almost completely ignored in the U.S., despite that it’s arguably the most rigorous to date (and the only study ever to study U.S. troops mental health both before and after deployment) — found that while the overall rates PTSD among U.S. veterans of OEI/OEF were much lower (about 5%) than the 20-30% found or predicted in other studies of either Vietnam veterans or veterans of the Iraq and Afganistan conflicts, combat experience (rather than mere deployment to war zone) roughly doubled the risk of developing PTSD.
This made Smith and colleagues wonder whether they could find baseline mental or physical health measures that seemed to predict greater risk of PTSD. The answer, presented in this new paper, seems to be Yes. It appears — unsurprising, in a way — that those who enter war in relatively poor physical, mental, or cognitive shape are more likely to be psychially overwhelmed.
In a combat environment, a large volume of visual, auditory, and other information must be interpreted and acted on without hesitation, which requires excellent cognitive abilities, an ability to manage extreme stress, think clearly under pressure, multi-task, and remain vigilant for extended times during prolonged periods of high operational tempo.46 47 Physical health is equally important because physically fit service members are better prepared to meet the physical rigours associated with military service. Lower physical health status has been associated with some diseases48 49 and increased injuries.50 In addition to the importance for basic health and military readiness, our study provides strong evidence that physical and mental health is essential for prevention of a large portion of PTSD after combat.
Smith notes that this bottom 15% of soldiers was actually healthier to start with than the bottom 15% of the U.S. population. Yet they still had about twice the number of self-reported mental and physical diagnoses (pre-deployment) than did their middle-of-the-pack peers (those scoring between 15% and 85% percentiles).
The beauty of this finding is that it suggests a fairly easy way to sharply curtail PTSD among combat veterans: As Smith puts it,
So though these individuals are being deployed, they seem to have diminished health before deployment. This presents an easily identifiable subpopulation for screening before deployment.