GIGANTE, Costa Rica — There was a ghostlike quality to Rudy Gonsior, an American former Special Forces sniper, on the morning he arrived at a jungle retreat to see if a vomit-inducing psychedelic brew could undo the damage years of combat had done to his mind.
Glassy-eyed and withdrawn, he barely spoke above a whisper and was much quieter than the six other veterans who had come to dredge up painful memories of comrades fallen in battle, thoughts of suicide and the scar that taking a life leaves on the psyche.
“I have traveled across continents to come to the jungle to do psychedelics,” marveled Mr. Gonsior, who had steered clear from drugs his whole life. “I guess this is what might be considered a Hail Mary.”
They had come to western Costa Rica to try ayahuasca, a substance people in the Amazon rainforest have imbibed for centuries. Some Indigenous communities regard the brew, which contains the hallucinogen DMT, as a powerful medicine that keeps them spiritually resilient and in harmony with the natural world.
The lodge the Americans visited late last year was a far cry from that, with a gleaming swimming pool and a sprawling deck that anchors well-appointed cabanas featuring splendid ocean views. Charging from $3,050 to $7,075 per person for weeklong retreats, the lodge is among the newest and priciest additions to a booming alternative healing sector.
Until relatively recently, only a few botanists, hippies and spiritual seekers gained access to the world of Amazon shamanism, which missionaries drove underground during colonization in much of the Amazon basin as they sought to convert Indigenous groups to Christianity.
But now, thousands of people from around the world make pilgrimages each year to the more than 140 ayahuasca retreat centers in Latin American countries where the substance’s use in ceremonial settings is legal or, as in Costa Rica, not explicitly outlawed.
Besides psychedelic ceremonies, which are often physically and emotionally draining, retreat organizers offer group therapy sessions, yoga classes, art therapy, meditation circles and warm floral baths.
Collectively, these centers have become an unlicensed and unregulated mental health marketplace for people searching for an alternative to antidepressants and other widely prescribed pharmaceuticals.
The draw of psychedelics has surged amid a growing body of scientific research that builds on promising studies in the United States and Europe from the 1960s and 1970s. Much of that earlier research was shut down after psychoactive substances were outlawed during the Vietnam War era — a response to concerns over widespread drug use on college campuses.
But in the last few years, the Food and Drug Administration designated psilocybin, the psychedelic component in what are commonly called magic mushrooms, and MDMA, the drug known as ecstasy, as “breakthrough therapies.” That rare designation allows scientists to fast-track larger studies that could pave the way to administering psychedelics as medicine.
Drinking ayahuasca can be dangerous, especially while taking certain pharmaceuticals, including antidepressants and hypertension drugs. It can also set off psychotic episodes for people with serious mental health conditions, like schizophrenia.
And while some retreats have strict rules and protocols that have been developed in consultation with medical professionals, the ayahuasca boom has sometimes been exploited by scammers and charlatans, and it has come under scrutiny for instances of sexual assault on vulnerable or impaired participants, including cases in Peru.
“You have to recognize that there’s a Wild West element” to ayahuasca retreats, said Dr. Matthew Johnson, a professor of psychiatry and behavioral sciences at Johns Hopkins University who has studied psychedelics since 2004.
In a controlled setting, he said, unleashing the brain can help patients revisit repressed trauma and generate new insights. So the medical establishment, once deeply skeptical of the therapeutic potential of psychedelics, is embracing “what is essentially a new area of medicine,” he added.
But Dr. Johnson worried that psychedelic retreats in general may be ill equipped to screen people for whom trips can be dangerous. In extreme cases, people have tried to commit suicide while high on psychedelics or experienced psychotic episodes that required hospitalization.
“These are powerful, powerful tools and they can put people in a very vulnerable place,” Dr. Johnson said. “That is not to be underestimated.”
Still, the growing buzz around psychedelic-assisted healing, which has been amplified by authors, celebrities and influential podcast hosts, has put places like the Soltara Healing Center, where the veterans went, at the forefront of a push to challenge conventional mental health care.
Melissa Stangl, a co-founder of Soltara, argued that responsibly run ayahuasca centers could be the seeds of a transformation.
“We are on the cusp of bringing psychoactive medicines into the mainstream health care system,” she said. “Once science really catches up to just how effective that is for people who aren’t being served by the current medical system, we can become allies.”
Before their first ayahuasca ceremony, the veterans met individually with two Peruvian “maestros,” or healers, from the Shipibo community in Peru.
“Their hearts are hardened,” said Teobaldo Ochavano, who helps run the nighttime ceremonies alongside his wife, Marina Sinti. “They seemed unable to experience love or joy.”
Ms. Sinti said years of interacting with foreigners on retreats had made it painfully clear why these rituals are in such high demand.
“People in the United States and Europe are very disconnected,” she said. “From each other and from the Earth.”
‘A Cult of Death’
Like many service members of his generation, Mr. Gonsior said he enlisted in the Marine Corps to avenge the attacks of Sept. 11, which happened when he was in high school.
In 2006, he said he deployed to western Iraq for the first of multiple combat tours. He and his men were constantly ambushed with powerful roadside bombs and shot at by snipers, he said, and 17 service members he deployed with returned home in body bags.
The experience, Mr. Gonsior said, turned him into a ruthless warrior.
“My sole goal was to survive,” he said. “I did a lot of things that I am not particularly proud of.”
Instead of relief for surviving, he felt a crushing sense of shame.
“It was just by dumb luck that I wasn’t shot and wasn’t blown up,” he said. “Like to the point where, statistically, I should be dead by now or at least seriously injured.”
In 2007, Mr. Gonsior said he joined the Army Special Forces, where he served as a sniper. It left him feeling that he had joined a “cult of death,” he said.
“The last 17 years of my life, my job in one way or another has revolved around death,” he said. “As I get older, it weighs heavy.”
Killing became mundane. But one life he took in Afghanistan in 2012 haunted him for years.
During a routine operation, Mr. Gonsior opened fire on a man on a motorcycle, believing he was an insurgent. Soon after, Mr. Gonsior learned he had killed an Afghan intelligence source working with his unit.
Mr. Gonsior said he didn’t allow himself to grieve that death properly or process the guilt until years later, when he was gripped by depression and bouts of rage that were sometimes set off by inconsequential things his children did.
Abstract thoughts about suicide eventually turned chillingly specific, he said. At the Veterans Affairs hospital where he sought help, Mr. Gonsior, 35, said he was urged to take antidepressants. He said he refused, based on the side effects he had seen fellow soldiers suffer.
Last year, after listening to a story about ayahuasca and trauma on the radio, he became fascinated by the idea that healing deep wounds requires grappling with their roots.
“There’s a lot of emotional wreckage, shipwrecks that are kind of down there,” he said.
By the time he and the other veterans filed into the darkened ceremony room, with its netted windows and cone-shaped roof, they had signed a lengthy hold-harmless agreement.
It warned of the “unlikely event of a psychotic episode,” the danger of drinking ayahuasca while taking antidepressants, and that psychedelic trips leave some people feeling worse “mentally, physically and emotionally.”
Dressed in traditional outfits, the Peruvian maestros blew tobacco smoke into the candlelit room, known as a maloca. Participants sitting on cots arranged in a circle stepped up to gulp a shot glass of the dark brown, sludgy ayahuasca brew.
Chris Sutherland, a 36-year-old Canadian soldier who said he recently retired on full disability for post-traumatic stress disorder, had come after years of panic attacks, binge drinking and periods of taking antidepressants that left him feeling that “I was no longer human.”
David Radband, a British former special forces soldier, said he came to the jungle hoping to drown out the rage that had consumed his life after he left the army. He said it had cost him custody of his children, landed him in prison for assault and pushed him to try to kill himself twice, once by hanging and once by stabbing himself in the gut.
“I was blocking emotions with anger,” said Mr. Radband, 34. “I was putting up a wall all the time.”
Juliana Mercer, 38, a Marine veteran, said she developed a condition called caregiver fatigue after spending four years looking after wounded service members in San Diego. When she deployed to Afghanistan in 2010, she said she experienced crippling fear every time she saw young, healthy Marines drive off the base.
“I was just so desperate to keep everybody safe,” she said.
It was quiet in the room when the maestros blew out the candles, save for the gentle lapping of waves from the nearby beach. But the silence was short-lived.
As the ayahuasca began taking hold, the Peruvians began pacing across the room slowly as they sang Icaros, high-pitched songs that the Shipibo regard as the crux of the healing process.
At times, their rhythm and cadence can be soothing and hypnotic, lullaby-like. But higher notes and fast-pace sequences can feel taunting or exasperating.
When ceremonies reach a crescendo, the room often feels like a state of controlled pandemonium. Bouts of loud vomiting pierce the singing. There is sometimes audible weeping in one corner and ecstatic laughter from across the room.
As dawn approaches and the ayahuasca starts wearing off, participants emerge from the room looking gaunt and dazed as the rational mind struggles to regain control.
“These experiences have a way of completely blasting people out of the mental ruts they’re stuck in and to look at a broader set of possibilities,” said Dr. Johnson at Johns Hopkins, one of several universities conducting clinical trials.
Unlike antidepressants, which numb symptoms of distress when effective, psychedelics appear to turbocharge the kind of healing process that results from psychotherapy, he added.
But he and other experts who cite the psychiatric promise of psychedelics worry about their use in retreats or other settings without adequate controls.
“The room for error is not having adequate medical support” in the rare instances when people have serious adverse effects, said Collin Reiff, a psychiatrist at New York University.
Still, Jesse Gould, a former Army Ranger who brought the veterans to Soltara, says the benefits of the jungle retreat experience outweigh the risks.
Mr. Gould said he created the Heroic Hearts Project, a nonprofit group that raises money to send veterans to psychedelic retreats, after stumbling into one at a low point in his life.
After leaving the Army and traveling a bit, he said he landed a comfortable job in finance that drove him to drink heavily and left him with “a feeling of dread about everything.”
When he sought help at the Department of Veterans Affairs in Tampa, where he lived, Mr. Gould said he was encouraged to take antidepressants, which held no appeal to him. In 2016, he quit his job and booked a retreat at a center in Peru.
The decision was radically out of character for Mr. Gould, 33, a strait-laced veteran who said he had avoided drugs his whole life.
“I definitely grew up in the D.A.R.E. generation,” he said, referring to the antidrug advertising campaign that began in the 1980s. “I was very much into ‘Just say no.’”
His first few ceremonies were brutal, Mr. Gould said, calling them “an all-out war” in which he vomited as many as 20 times in one night and felt like he was pushed “to the edge of sanity.”
But in the months that followed, he said his depression mellowed, his crippling social anxiety melted away and his mood swings, which had felt like a “tug of war in my brain,” ceased.
“It seemed to almost rewire my brain,” Mr. Gould said.
Since then, Mr. Gould and his team have raised more than $250,000 to pay for psychedelic retreat “scholarships” for dozens of veterans. And they have infused the movement to decriminalize psychedelics with testimonies that belie the stereotype of New Age stoners.
“People instantly have the image of a hippie,” he said. “But because of my service, a lot of people that are in a completely different demographic tend to listen.”
‘Another Layer of Understanding’
As their weeklong retreat came to an end, Mr. Radband, the British soldier, said the ceremonies had reignited his desire to live.
“You know, I tried to kill myself twice, but I’m not ready to die,” he said. “I have so much more to give.”
Mr. Sutherland, the Canadian, said one of the ceremonies had been “the most terrifying night of my life, more terrifying than any combat I have ever been in.” But collectively, he said, the trips helped him overcome a longstanding fear: “I am not a sociopath,” he said.
“I was always worried that I was evil, but I was shown where my compassion lies,” he said.
Mr. Gonsior, the American sniper, likened the experience to a “final surrender” that was grueling but restorative.
“You have so many experiences that run the gamut from absolute terror to pure joy,” he said. “You realize there’s another layer of understanding there.”
On the last day, as Mr. Gonsior was waxing poetic about the universe and how all living beings are connected, Mr. Gould couldn’t resist getting in a little jab.
“There’s a hippie inside every veteran,” he said.