New-onset, self-reported PTSD symptoms or diagnosis among deployed military personnel with combat exposure occurred at about a threefold higher rate than that in nondeployed military personnel, according to a report in the February 16 BMJ.

Tyler C. Smith, PhD, and colleagues based their findings on 77,047 active military volunteers from the ongoing Millennium Cohort study, which was designed in the late 1990s to prospectively answer health concerns associated with military service. Participants were surveyed before the wars in Iraq and Afghanistan (from July 2001 to June 2003) and again three years later. The primary outcome measure was self-reported PTSD per the PTSD Checklist–Civilian version using DSM-IV criteria. Data from 50,128 participants were included in the analysis.

The researchers found that deployment without combat exposure was not associated with an increase in PTSD. Although deployed soldiers with combat exposure had the highest incidence of PTSD (7.6%), deployed soldiers without combat experience had the lowest risk (1.4%), compared with nondeployed soldiers (2.3%). Combat exposure was defined as witnessing any of the following: “a person’s death due to war, disaster, or tragic event,” “instances of physical abuse (torture, beating, rape),” “dead and/or decomposing bodies,” “maimed soldiers or civilians,” or “prisoners of war or refugees.”

Odds ratios of developing symptoms of PTSD were increased in those who had combat experience (compared with those who were not deployed) in all branches of the US armed services—Army (3.59), Air Force (3.38), Marine Corps (2.78), and Navy/Coast Guard (2.48). In addition, the researchers found that at the three-year follow-up, 45.7% (455 of 995) of those who had PTSD at baseline still had persistent symptoms.

“These data emphasize that specific combat exposures, rather than deployment itself, significantly affect the onset of PTSD symptoms postdeployment,” said Dr. Smith, Director of the Department of Defense Center for Deployment Health Research, Naval Health Research Center, San Diego, in an interview with NeuroPsychiatry Reviews.

Additional risk factors for PTSD symptoms, according to the investigators, were female gender, younger age, high school education or less, never married or divorced status, black non-Hispanic, having enlisted, Reserve/National Guard members, Army personnel, health care specialists, service supply and functional specialists, current smokers, or having a history of problem drinking.

Study limitations included potential reporting bias, as follow-up questionnaires were not available from 29% of the participants and PTSD was self-reported. Soldiers who were deployed were more likely to be male, born between 1970 and 1979, less educated, on active duty, and combat specialists, compared with nondeployed soldiers.

Dr. Smith and colleagues theorized that the higher incidence of PTSD in troops who participated in combat might result from multiple factors. “The unpredictability and intensity of urban combat, constant risk of roadside bombs, multiple and prolonged tours, and complex problems of differentiating enemies from allies can leave many troops with high stress levels and possible lasting health consequences,” the researchers stated.

Although PTSD in combat-exposed troops might not be preventable, certain subsets of the population may be more or less vulnerable to PTSD symptoms, the authors said. Identification of these individuals could enhance the development of preventive strategies, as well as lead to an earlier diagnosis, improved access to care, and decreased morbidity.

—Andrew Wilner, MD

Suggested Reading
Smith TC, Ryan MA, Wingard DL, et al. New onset and persistent symptoms of post-traumatic stress disorder self reported after deployment and combat exposures: prospective population based US military cohort study. BMJ. 2008;336(7640):366-371.

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