CORVALLIS, Ore. — In the Vietnam War, the second-largest contingent of soldiers fighting North Vietnam came from Korea. Now, 45 years later, roughly 40% of Korean Vietnam veterans have post-traumatic stress disorder, a rate higher than their American counterparts.

While PTSD is usually thought to stem from a single horrific experience, a new study from Oregon State University researcher Carolyn Aldwin and Korea Military Academy researchers Hyunyup Lee and Sungrok Kang found that fighting in an environment plagued by chronic stressors like heat, humidity and bugs greatly exacerbated Korean Vietnam veterans’ PTSD later in life.

“In some ways, the malevolent environment may be a bigger risk factor for PTSD than the trauma itself, and that was very surprising to us,” said Aldwin, an OSU Public Health and Human Sciences researcher who has been studying the long-term effects of military combat for more than 25 years.

“I’m not certain that malevolent environments are traumatic in themselves” — though they can be, she said, as in the trenches of World War I — “but if you’re getting eaten by bugs and have sand in all your food, on top of everything else … It’s a stress that may exacerbate the general stressfulness of war.”

The implications of these results, published last week in the journal Psychological Trauma, stretch far beyond the military. Civilians living in crime-ridden neighborhoods or bombed-out villages can face similar mental health issues.

“In general, you could look at impoverished environments as perhaps also being malevolent, to the extent that people face physical toxins and also psychological toxins,” Aldwin said.

To conduct the study, the researchers sent a survey to veteran groups in South Korea in 2017. They were able to use data from 367 veterans, most of whom had served in combat-related positions and whose average age was 72.

The survey included questions about four unique war stressors: “Combat exposure” involved the number of times soldiers had been under enemy fire. “Malevolent environment” assessed harsh situations they faced on a day-to-day basis, such as annoying insects or heavy gear. “Perceived threat” referred to soldiers’ fear for their own safety. And “moral injury” gauged how soldiers felt their actions in war violated their own moral or ethical beliefs.

They also analyzed three “protective” factors that could help mitigate the impact of war stressors: “Optimism,” “unit cohesion” during deployment and soldiers’ “homecoming experience.”

The researchers found that malevolent environment was the most consistent predictor of PTSD, depressive symptoms and anxiety symptoms later in life.

Moral injury also contributed to PTSD, and both moral injury and perceived threat were slightly associated with anxiety symptoms.

The effect of combat exposure actually became statistically insignificant when compared with the effects of the other three stressors.

“Malevolent environments, such as uncomfortable climate or awful smell, may seem to be less severe stressors compared to life-threatening events in the battlefield,” the study says. “However, chronic and daily stressors, rather than less frequent severe life events, can have a serious impact on individuals’ mental health.”

The impact that environment can have on mental health may be an important motivation behind the U.S.’s efforts to provide American-style housing and amenities for troops in the Middle East, Aldwin said.

For this study, the team focused on Korean veterans in part because there is little to no literature worldwide on post-war mental health issues among Korean vets, even though their rate of PTSD is higher than U.S. Vietnam veterans, an estimated 30% of whom will have PTSD in their lifetime.

The researchers speculate that this higher rate may be because most Korean soldiers in Vietnam were ground troops, and thus exposed to a lot of trauma and environmental stressors. Social stigma around mental health treatment in that era may have also played a role, as Korean veterans may have been unlikely to seek or be able to find treatment for PTSD when they came home.

Future studies will compare Vietnam veterans with veterans from the Persian Gulf and post-9/11 wars.

College of Public Health and Human Sciences

About the OSU College of Public Health and Human Sciences: The first accredited college of public health in Oregon, the college creates connections in teaching, research and community outreach while advancing knowledge, policies and practices that improve population health in communities across the state and beyond.

Story By: 

Molly Rosbach, 541-737-0783, [email protected]


Carolyn Aldwin, 541-737-2024, [email protected]

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