Which soldiers are most at risk for PTSD?

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.

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After "Gulf War (I) Syndrome" claimed hundreds of thousands of victims, Congress mandated that troops about to be deployed into combat must be given health exams before being shipped out.

In 2003, SecDef Rumsfeld decided that overthrowing the Hussein regime was such an all-out emergency that this law had to be broken: none of the troops sent to the Bushkrieg got those exams.

Perhaps the best way to prevent combat PTSD depends less on medical examiners and more on voters.

By Pierce R. Butler (not verified) on 20 Apr 2009 #permalink

I don't recall directly the study or assessments Pierce Butler refers to in his comment above -- the ones he says were cancelled by Rumsfeld. But to be clear: the health assessments in Millenium Cohort Study described in the post above did indeed take place, for that study began in 2001, before the war, and has continued on its own track since then. It's already yielding invaluable information and will continue to do so.

Butler's larger point stands, of course: You can reduce the risk of combat-related PTSD quite effectively by not engaging in wars of choice.

My email archive contains a relevant circa-5/1/03 URL-less story purportedly from TomPaine.com (which I cannot find by searching there), but I googled keywords from same to locate this:

Rumsfeld Blinks; Pentagon Reverses Policy at 11th Hour, Averts 'Public Relations Nightmare'
WASHINGTON, April 30 /U.S. Newswire/ -- Averting what one veterans' advocate called a "public-relations nightmare," the Pentagon reversed itself yesterday by announcing that it has now decided to perform medical exams on troops returning from the Iraq war, as required by law.

The military must test troops both before and after deployment, according to Public Law 105-85, but the Pentagon has admitted that it did not test troops bound for the Iraqi conflict, and it had said it would not do so upon their return. ...

By Pierce R. Butler (not verified) on 20 Apr 2009 #permalink

Ah! Nice find, Mr. Butler -- thanks for putting this up. Interesting Rumsfeld reversed himself on that. But good thing he did.

Another real loss that occurred not long after was the pulling of the plug, for reasons not quite clear, on a major update to the National Vietnam Veterans Readjustment Study that had been scheduled for the mid-1990s. Such a follow-up might have been highly valuable for a number of reasons. But as I researched my PTSD story in 2007 and 2008, a number of people told me that the update was killed, apparently by the VA, for reasons that no one quite understood and few were willing to speculate about.

David Dobbs,

I very much enjoyed your Sci Am PTSD article and passed on a read-it recommendation to my brother who works with veterans.

I add a general observation. I think our society tries to ease-around or escape some of life's inherent difficulties. After some difficulties several years ago the realization crystalized for me that significant trauma - which can be well short of witnessing death - inevitably produces a subsequent period of psychological wrenching. You simply have to bear with it. This is perhaps analogous to the aches you endure after an injury. In neither case do I find drugs helpful.

On another point, your interest in the brain/neural topic could find traction with the growing conundrum over the determination of individual personalities. I grew up around some monozygotic pairs and beyond appearances they were different beings. This resonates with the recent apparent tanking of the Human Genome Project's Common Disease/Common Genetic Variants hypothesis. I explore these topics and more at

A final comment. Keep pushing practical/helpful articles in Sci American.

Ted Christopher
Rochester, NY

By Ted Christopher (not verified) on 20 Apr 2009 #permalink

Nice piece. I think it adds a lot to the understanding of the issues.

But there may be a small aspects of this that got missed. First, there is the matter of simple expectations. Men who are weaker mentally and/or physically are not unknown quantities to their peers. When they start to lose it or otherwise lose focus it is expected. It isn't like anyone encourages them to show the effects of the stress but when they look frayed around the edges nobody grabs goes out of their way to coach or encourage them either.

The unwritten rule is you knew the goofy kid that was dragging ass and wining was going to get the worse of it so nobody says much. Nobody expects more and nobody is willing to invest the time and effort to get more out of them. Everyone just shrugs and waves goodbye.

Second, employment of personnel is not uniform within any unit. People who are physically fitter, more skilled and mentally alert are given positions that put them in charge, and to some extent control, over their surroundings and circumstances. Even if they lack control they often know in advance, by way of their contacts and increased awareness, what is coming. They often have time to mentally prepare themselves and the situation seems far more understandable and far less random.

The lower scoring guys get put on jobs that keeps them on the defensive, guard the truck, and for the most part free of decision making and control of their surroundings. they are often kept completely in the dark as to the wider situation and are unaware of coming events before they actually happen. Everything comes as a shock.

Situations where they are forced to hunker down and take it. Having little or no awareness of what is coming and being entirely unable to exert control is perhaps the hardest of all situations to deal with mentally.

PTSD is not a matter of will or self control and people can't 'snap out of it'. But the stress of combat duty is not made any easier when people withhold support and low expectations are absorbed by the most vulnerable population.

Or when more vulnerable people are employed in a manner that limits their ability to maintain awareness and maintain a sense of control over their situation.

Nice post. I would point out, though, that the 15% line could be expected to shift, depending upon the sample of the population that is inducted into service.

The Army's well-known loosening of its service requirements could well have shifted that line. Even so, it would be a good idea to limit the combat exposure for this subpopulation. This would be important not only for the at-risk soldiers, but also for the soldiers who serve with them.

I suspect that this kind of limitation would be illegal in the civilian world, or at least open to legal challenges on the basis of discrimination. But it is hard to imagine that the military would have such constraints. Might be worth asking someone who knows military law.

'In 2003, SecDef Rumsfeld decided that overthrowing the Hussein regime was such an all-out emergency that this law had to be broken: none of the troops sent to the Bushkrieg got those exams.'

George Patton's career was almost ruined for slapping two soldiers! And Rumsfield gets the Presidential Medal of Freedom. How many mentally scarred young men are out there because of this decision? Impeach the bum.

David Dobbs @ # 4: Interesting Rumsfeld reversed himself on that.

Well, so he claimed. I lack the PubMed-fu to determine with confidence whether the promised/mandated post-return exams did take place (or if they're still occurring), but I can say with great assurance that a Bushevik's promises need to be input with maximum NaCl.

... the update was killed, apparently by the VA, for reasons that no one quite understood and few were willing to speculate about.

It's difficult to distinguish an above-average concentration from the background odor, but I detect a whiff of Rattus.

toby @ # 8 - It's too late to impeach, but not to indict...

By Pierce R. Butler (not verified) on 21 Apr 2009 #permalink

Joseph wrote:

Nice post. I would point out, though, that the 15% line could be expected to shift, depending upon the sample of the population that is inducted into service.

Quite true; I was writing perhaps a bit too quickly. The more rigorous way would be to i.d. the absolute mental and physical health scores that conferred extra vulnerability (rather than just percentiles within the test results) and use those as markers for whatever measures you were going to take to either avoid combat or try to instill more resilience (via Battlemind-type programs).