Article review: Morphine as prevention of PTSD among Marines in Iraq

Making minor waves this week is a study in the New England Journal of Medicine (NEJM) showing lower rates of posttraumatic stress disorder (PTSD) among injured soldiers given morphine during emergency medical care. The credibility of the study is strengthened by its use of 696 (i.e., a “large sample”) recent medical records from a well-designed Naval trauma registry used in Iraq (for those of you don’t know the structure of the US military, this would include Marine Corps data as well).

The NEJM morphine article is predicated upon the theory that PTSD is the result of experiencing a traumatic event plus your interpretation of the immediate aftermath of that traumatic event. The worse your immediate reaction to a given traumatic event, the more you associate the memory of that traumatic event with debilitating anxiety (a negative “memory consolidation”), and the more likely you will be to develop PTSD. Several researchers have posited that breaking the association between the trauma and the “peritraumatic” distress (the anxiety “around the trauma”) is the key to preventing the development of PTSD. Most have proposed to do this using medication.

The primary aim of pharmacotherapy is to decrease or impede memory consolidation and the associated conditioned response to fear after a person goes through a traumatic event. (p. 111)

This means that everybody who experiences some traumatic event would have to get the medication — even though not everybody in that group is expected to develop PTSD. In fact, most are expected not to develop PTSD. Numerous studies have shown that no matter what type of traumatic event is considered, none makes more than half of those exposed to that type of event develop PTSD. Among Iraq war soldiers, for instance, rates of PTSD are in the 20% range. Remember that PTSD is a collection of symptoms — intrusive thoughts, flashbacks, etc. — that persist after a month has passed (up until a month, these symptoms are not considered pathological, and for most people, they subside without long-term disability). So, giving medication to everyone who experiences a trauma is a “secondary prevention” strategy — you know someone in the group will develop the problem, but don’t know who, so you give the “cure” to everyone.

Small does of morphine are often used in trauma centers (medical trauma, that is), and lower levels of opioids have been implicated in the development of PTSD (morphine is an opiate, opioids are the human-produced equivalent), and thus the idea that soldiers treated with morphine for their injuries would be less likely to develop PTSD makes sense. Of the 696 injured soldiers, 243 eventually developed PTSD and 453 did not. Of those 243 who developed PTSD, 147 (60%) had received morphine; of those 453 who did not develop PTSD, 346 (76%) had received morphine. Sixty percent compared to 76% may not seem like a big difference to you, but when you do the statistics you come up with an odds ratio of .47, meaning that the odds of developing PTSD were half when given morphine than when not given morphine.

These results stood up to the usual battery of accounting statistically for things like type of combat event, injury severity, amputation, and whether the soldier had a concussion or not (soldiers with more serious traumatic brain injuries were excluded from the review of records). Notably, the rates of serious injury were somewhat higher among those who did not develop PTSD, supporting work by Delahanty (Kent State) showing that the body’s chemical production (specifically cortisol) during more serious injuries actually counteracts the development of PTSD; the presence of injuries on its own (i.e., compared to no injuries) makes it more likely PTSD will develop, but the more serious those injuries are, the less likely it is that PTSD will develop.

Okay, so what? Well, besides the obvious that morphine use following potentially traumatic events might be examined prospectively to get a sense of its potential to specifically prevent PTSD (and not as a by-product of medical care as it was in this study), this study puts into perspective the association of opiate abuse and post-conflict situations throughout history and around the world. From Odysseus in the Land of the Lotus Eaters to the heroin addicts among Vietnam vets and even the old Sikh men I met in Punjab chewing balls of raw opium to deal with memories of the multiple conflicts of that region of India, it seems that soldiers’ self-medication with opiates may have always been a an indication of something their bodies knew they had missed at the time of their trauma. Waxing poetic aside, perhaps studies like this week’s article in NEJM will be able to provide them relief at the time of trauma so that they don’t seek it out later with such debilitating consequences.


2 Responses to “Article review: Morphine as prevention of PTSD among Marines in Iraq”

  1. 1 Sarah Sass January 17, 2010 at 1:12 pm

    Andy, thanks for posting. Although there are some methodological problems from a nitpicky research standpoint (e.g. reliability of PTSD dx is not available and can be a problem in clinical settings), it is suggestive of an intervention window for those with a high probability of undergoing trauma (e.g. soldiers).

    Here’s another recent paper you may already know about, focusing on the reconsolidation phase of memory and possible ways to intervene at that stage:

  2. 2 andyrasmussen January 19, 2010 at 10:51 am

    Thanks for the comment, Sarah. Indeed, diagnoses in clinical settings are reliably unreliable, although of course valid in that clinical settings are the reality in which patients get their care. What I like about this article is the real-world setting. It provides some support for the memory consolidation/reconsolidation approach to PTSD that seems to be the most promising for prevention purposes. Thanks for the link–I’d also refer readers to the work of Joe LaDoux (NYU) and Roger Pittman (Harvard, I believe).

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