17 AUGUST 2006
Combat: Bad for your head
A reassessment of the psychological cost of combat shows that 19 percent of male American veterans of the Vietnam war had post-traumatic stress disorder. According to this new analysis of data collected during the mid-1980s, 9 percent of the vets still had symptoms as much as 20 years after they last saw combat.
The new figures fall between two previous estimates. In 1988, the National Vietnam Veterans Readjustment Study (NVVRS) estimated that 31 percent of Vietnam vets had had PTSD, while the Centers for Disease Control (CDC) put the proportion at 15 percent.
The Vietnam war highlighted the issue of wartime damage to the psyche after a considerable number of American veterans returned home with nightmares and uncontrollable memories of the war. Post-traumatic stress disorder was defined on the basis of these and other symptoms, such as a persistent state of "fight-or-flight," numbness, hyper-vigilance, and an exaggerated startle response. The condition typically eases over time, says Bruce Dohrenwend, chief of research in the department of social psychiatry at the New York State Psychiatric Institute.
The 1988 estimates were intended to bring sanity to a field marked by controversy, but they took immediate fire, says Dohrenwend. "There was evidence early on that the CDC study grossly underestimated the rates," yet skeptics were also "highly critical" of the readjustment (NVVRS) study, whose "numbers seemed awfully high to skeptics."
With his colleagues, Dohrenwend, who is also a professor of epidemiology at Columbia University, applied modern standards to reassess the level of PTSD in 260 of the NVVRS subjects. By studying tape recordings of the NVVRS interviews (held between November, 1986 and February, 1988) Dohrenwend's researchers reevaluated whether the vet had ever had war-related PTSD symptoms, and whether the PTSD was present at the time of the interview.
Overall, Dohrenwend and collaborators concluded that about 19 percent of the NVVRS sample had PTSD due to wartime exposure, not the 31 percent found by NVVRS.
Three factors explained the lower rate, Dohrenwend says. First, symptoms that surfaced before the war or long after it were excluded as unrelated to combat. Second, today's definition of PTSD requires at least a moderate impairment in social functioning, such as holding a job, and some of the PTSD cases failed that standard. Third, the few cases where combat exposure could not be corroborated by military records were eliminated.
Photo: National Archives
To link the effect (PTSD) with the putative cause (combat) the researchers tried to measure each vet's exposure to the physical terror of warfare by assessing
- the veteran's role in the military,
- the casualty rate of the veteran's large military unit,
- the monthly U.S. casualty rate in Vietnam during each vet's service, and
- the number of fellow soldiers in the veteran's small military unit killed in action while he served in Vietnam.
In contrast to a previous estimate, that 15 percent of American military forces saw combat, Dohrenwend concluded that closer to 50 percent had had experiences that threatened their "physical integrity" -- their lives.
Combining the new estimates for the prevalence of PTSD and exposure to physical danger revealed a solid link between exposure and disease. For example, while only 1 percent of vets with the lowest combat exposure still had PTSD when the NVVRS interviews were done, 28 percent of those with the highest combat exposure did have the condition. "That's extremely important," says Dohrenwend. "If you can show with defensible measures that an increase in the severity of exposure is followed by an increase in the rate of PTSD, that's as near as you can come to finding a causal relationship in this type of study."
A "conservative estimate that one-fifth of male veterans in Vietnam had war-related PTSD at some time, and that one-tenth had PTSD that persisted for over a decade" may seem alarming, but Dohrenwend notes that the large majority of veterans did not develop war-related PTSD. "There seem to be protective factors that reduce vulnerability."
Getting a better grip on these protective factors could be helpful as American veterans stream back from the Iraq war, Dohrenwend suggests, because Iraq and Vietnam have similarities. "Both are wars without fronts, where it is often difficult to tell peaceful civilians from enemy combatants, and there is no completely safe place."
-- David Tenenbaum
• The Psychological Risks of Vietnam for U.S. Veterans: A Revisit with New Data and Methods, Bruce P. Dohrenwend et al, Science, 18 Aug. 2006.