Vietnam Post-Traumatic Stress Syndrome Rate Re-Evaluated

NEW YORK, Aug. 21 -- The widely cited estimate that one in three Vietnam veterans suffered from post-traumatic stress disorder (PTSD) is too high, but the psychiatric toll on soldiers was still substantial, according to a study here.

Taking into account new data, about 18.7% of veterans had developed war-related PTSD during their lifetimes and 9.1% were suffering from the disorder 11 to 12 years after the war ended, Bruce Dohrenwend, Ph.D., of Columbia University, and colleagues, reported in the Aug. 18 issue of Science

The earlier estimate implied that the "Vietnam War took a severe psychological toll on U.S. veterans," the researchers said, adding that "our results provide compelling reasons to take this message seriously."

The debate over the psychological effects of a "war without fronts," such as Vietnam or the current conflict in Iraq, began in 1988, when the CDC reported lifetime PTSD rates of 14.7% and said 2.2% of vets had PTSD 11 to 12 years after the end of the Vietnam war.

The CDC study, though, was contradicted the same year by the National Vietnam Veterans Readjustment Study (NVVRS) - an analysis of a representative sample of 1,200 veterans that found that 30.9% had developed PTSD during their lifetimes and that 15.2% were suffering from PTSD at the time.

The debate was heightened when critics pointed out that only 15% of the military personnel in Vietnam were combat troops, while twice that proportion was suggested to have incurred PTSD during the war.

Dr. Dohrenwend and colleagues constructed a new exposure measure by re-examining records of the NVVR study's 260 in-depth diagnostic interviews, incorporating military records that were not available at the time, and in some cases corroborating soldiers' self-reported stress by consulting newspapers reports of military action.

They found:

• No evidence that soldiers falsely reported traumatic incidents.
• A strong dose-response relationship between traumatic events and the occurrence of PTSD.
• Lower but still substantial psychological costs for veterans.

While the PTSD rates remain high, Dr. Dohrenwend and colleagues said, it's important to note that the majority of soldiers with high and extremely high exposure to traumatic events did not develop the disorder.

The researcher noted that in a war such as Vietnam or Iraq, the stress of combat falls not only on front-line soldiers, but also upon those in support roles, often far from combat zones. In fact, the researchers noted, at least half the military personnel in Vietnam were involved in combat at one time or another even if they were not formally designated as combat troops.

To capture that complexity, they constructed a "military historical measure" that included information such as a veteran's military specialty, whether he received a Purple Heart, the monthly killed-in-action rate during his Vietnam service, and whether he was in the country during the Tet offensive of 1968.

The measure was divided into four categories - low, moderate, high, and extremely high exposure. For the most part, the researchers said, a soldier's self-report was consistent with the records-based measure.

For example, 96.5% of those classified as having low exposure on the records-based measure self-reported they had low or moderate exposure in the 1988 NVVRS. Also, 72.1% of the veterans classified as very high on the new measure has reported themselves as having high exposure in 1988.

Dr. Dohrenwend and colleagues also found a clear dose-response relationship between exposure to traumatic events during the war and having PTSD in 1988. Less than 1% of those in the low category of the records-based measure had a current diagnosis of PTSD in 1988, compared with 14.4% of those with moderate exposure, 27% of those with high exposure, and 28.1% of those with very high exposure.

The "most newsworthy finding" of the study is that the 1988 study overestimated the prevalence of PTSD, according to Richard McNally, Ph.D., of Harvard.

"By increasing the accuracy of our prevalence estimates, Dohrenwend et al. have performed a valuable service," Dr. McNally said in an accompanying Perspective article.

But, Dr. McNally said, two other findings are equally important - the verification of the dose-response relationship and the fact that few if any veterans exaggerated or falsified their claims.

The study was supported by the National Institute of Mental Health (NIMH) and by the New York-based Spunk Fund, Inc.