Patrick Flatley, a former Green Beret who served multiple tours in Iraq and Afghanistan, underwent the treatment in 2022. He described the experience as immediate: "My head started to tingle. I could feel my brain getting soothed, like it was getting what it needed."

Flatley's injuries began early. He joined the Army at 19 and accumulated head trauma first as a paratrooper jumping with 70 pounds (32 kilograms) of gear, then as a mortarman. In 1994, while serving as a Green Beret sniper, two U.S. Army helicopters were mistakenly shot down by U.S. Air Force fighter jets in northern Iraq. Flatley had frequently ridden those helicopters but was bumped from his spot by a last-minute personnel change. The nightmares that followed never stopped: "It was the same over and over. I never had a good dream for 25 years," he said.

After retiring, he became so tense and angry that he sometimes woke with a mouth full of blood from breaking his molars in his sleep. Crowds, traffic and the whir of helicopters triggered fight-or-flight responses. Flatley credits the ibogaine therapy with allowing him, as he put it, to finally come home from the war. For roughly four years afterward, he had no nightmares about the war. His PTSD isn't gone, but he says it's manageable.

What are the study's limitations?

The results are the most extensive evidence to date of ibogaine's long-term effects on PTSD, depression and anxiety — but the researchers urge caution. Because the study was only observational, they could not control for additional treatments during the follow-up period:

• 12 participants received therapy or counseling
• 3 took psychotropic medications such as standard antidepressants
• 23 took at least one psychedelic substance, ranging from microdosing to dedicated retreats

The most common additional psychedelic was 5-MeO-DMT, a short-acting compound that induces feelings of profound awe. Veterans in the study agreed to delay taking it until after the first month.

"We couldn't say that this one-year effect is due solely to that initial ibogaine experience," Rolle said. Even so, the researchers' analysis suggests lasting improvements overall, including among participants who pursued no additional interventions.

"For a single treatment to deliver 12 months of relief to some people is very exciting," said Jennifer Lissemore, Ph.D., a postdoctoral scholar and co-lead author. "If a treatment is known to have durable effects over the course of a year or more, that gives you much more reason to pursue it." Afik Faerman, Ph.D., is the other co-lead author; co-senior author Nolan Williams, M.D., led the work until his death last year.

What comes next?

Ibogaine has been a Schedule I drug since 1970, forcing patients to travel to Mexico, Canada or other countries where treatments are legal. But interest is growing. In April, President Donald Trump signed an executive order to accelerate research on and FDA approval of psychedelic drugs for serious mental illness, citing the toll on veterans: more than 6,000 die by suicide each year, double the rate of the nonveteran adult population.

Encouraged by the new findings, the Stanford team plans to study ibogaine in a different population: Ukrainian refugees, mostly women, with war-related PTSD. Brain imaging from the veterans showed small structural changes one month after treatment — slight increases in cortical thickness (the brain's outer surface, responsible for reasoning and language) and subcortical volume (deeper regions handling emotion and memory), plus a slight decrease in predicted brain age. The researchers stress these findings are preliminary and do not yet explain how ibogaine works, as the neurological mechanisms remain unclear.

"We are optimistic the future of ibogaine research will lead to effective treatment for individuals suffering the debilitating effects of PTSD," Rolle said.