What if you could predict PTSD in combat troops? Oh, who cares...

Photo: Tyler Hicks, via Scientific American

What if you could predict which troops are most likely to get PTSD from combat exposure -- and takes steps to either bolster them mentally or keep them out of combat situations? A new study suggests we could make a start on that right now -- and cut combat PTSD rates in half by simply keeping the least mentally and physically fit soldiers away from combat zones.

The study was part of the Millenium Study, huge, prospective study in which US Department of Defense researchers have been tracking the physical and mental health of nearly 100,000 service members since 2001. This is the largest, most thorough, robust, and sizable study of troop health being done -- though, for reasons I'll touch on in a minute, many of its results are going ignored by the larger research community and the press. Its great value is that it's big, and it began tracking the health of these servicemembers in peacetime, so it is in a prime position to track actual changes in health brought about by military service during wartime.

In this case, the study set out to

Determine if baseline functional health status,... predicts new onset symptoms or diagnosis of PTSD among deployed US military personnel combat exposure.

In other words: Might we already have measures of mental and/or physical health that let us predict which service members are most likely to get PTSD from serving in a combat zone?

The answer is a fairly emphatic Yes. The study found that the least healthy 15% of the troops in the study who saw combat accounted for well over half -- 58% -- of the post-combat PTSD cases, as indicated by either the study's own criteria or by self-report of a PTSD diagnosis from the soldiers during follow-up.

This is a pretty stunning result. And it certainly suggests that, as the study put it, "more vulnerable members of the population could be identified and benefit from interventions targeted to prevent new onset PTSD." The beauty of this finding is that fairly general measures of health are the indicators, so you can predict a lot from fairly simple and easy-to-collect data. Obviously not all of the 15% who scored lowest on PTSD; but that bottom 15% accounted for more cases than do the entire remaining 85%. So at a time when we are much concerned with reducing PTSD in combat troops, it seems fairly plain that we could cut the PTSD rate by more than 50% simply by keeping the least healthy 15% -- as measured by fairly simple health questionnaires we already have in any and -- out of combat zones.

The paper doesn't discuss how we would go about doing that. The two most obvious options are to either not accept people who score low on health measures or to accept them into the military but make sure they are given noncombat area assignments.

Strangely, and despite a river of news stories on PTSD this finding has gotten virtually no press attention. One reason may be that it was published in a British journal -- the British Medical Journal, or BMJ. Why is a study funded by the United States, conducted by an ace team of US Department of Defense researchers, and having to do with the physical and mental health of US soldiers published in a British journal rather than an American journal? This is a rich and dangerous question. I'll offer one possibility: this study appeared in the British Journal because its more fundamental finding -- that the overall PTSD rate caused by service in Iraq and Afghanistan was much lower (7.3%) than the rates that, though based on questionable studies and contaminated by the conflation of symptoms with disorder, have been reported and insisted upon by those who dominate the study and treatment of combat PTSD. (I noted this discrepancy in my Scientific American feature on PTSD this April; that story has much more on this tension about PTSD rates in our soldiers.)

Note that I offer this as a suggestion rather than as documented fact. I do not know the submission history of this paper, or of the same authors' more substantial paper on PTSD rates found in the Millenium Study, published by the same researchers early in 2008; that study found that PTSD rates in veterans of the Iraq and Afghanistan wars were running at around 6 to 8% rather than the 20 to 30% found by other studies. (That study too was published in BMJ and ignored by the US press and the VA.) I twice attempted to reach the researchers to ask whether they had submitted the earlier paper to any US journals, but I was not able to get a response from them or from the DOD public information officers. So it is conceivable that for some reason -- though I can imagine what -- these US researchers studying PTSD in US soldiers chose to submit their US-funded research findings to a British journal rather than to one of the obvious US journals, such as the Journal of the American Medical Association, the New England Journal of Medicine, or the American Journal of psychiatry.

I suspect it more likely, however, that this paper was submitted to at least some major American journals and then turned down because of damning comments by peer reviewers from the US PTSD research establishment, which has been energetic in its attacks on any findings that contradict with its own, much higher assessment of rates. I'd love to hear a more plausible explanation of why these studies ended up at BMJ. But even such an explanation wouldn't really explain why these studies are going so roundly ignored here in the U.S.

In any case, these findings on gross health-status predictors for PTSD risk should in theory be helpful aside from arguments about overall rates. It's a shame this finding -- and many others from this robust long-term study -- is getting neglected.