“In the beginning I was very gung-ho on drugs. I did a lot of the early studies for drugs for PTSD. But we very quickly realized they don’t work very well,” he said. “Every veteran since Homer has been doping himself up to keep his issues under wraps, but it doesn’t help process the trauma.”

In the 2000s Dr. van der Kolk published one of the first studies about the effects of yoga on PTSD. “It had very good results. After eight weeks, six months, the positive effects are still there,” he said. He has since made yoga a core part of his practice.

Long before medical researchers began trying to document benefits, veterans sought out the healing potential of the world beyond the doctor’s office. The first person to walk the entire Appalachian Trail, Earl Shaffer, had just come home from World War II and told friends he needed to “walk the Army out of my system, both mentally and physically.” After Vietnam, hundreds of veterans sought refuge in the wilderness.

“Most of my work is being driven by the veterans,” said Daniel Libby, a Yale-trained psychologist who teaches yoga at a veterans center in Oakland, Calif., run by the Department of Veterans Affairs. “They don’t want to be on medications. Yoga offers a therapy that is self-empowering. You don’t have to rely on the medical system.”

In 2010, Mr. Libby surveyed the department’s health system and found that 28 percent of hospitals offered yoga. Now he estimates that it is more than 60 percent.

Dr. Barbara Rothbaum, a psychologist at Emory University who runs an intensive two-week PTSD treatment program, complements her traditional therapies with alternative ones.