The latest strike against the increasingly popular therapy is a study of U.S. service members with persistent concussive symptoms, including headaches, balance problems, fatigue, forgetfulness, irritability and anxiety.
Those who spent 40 sessions in a pressurized chamber breathing pure oxygen saw no more improvement than a control group that completed the same number of sessions in a lower-pressure chamber breathing normal air.
Both groups, however, fared significantly better than a third group that received only standard care. The gains most likely resulted from some combination of a placebo effect and the daily ritual of interacting with the study staff, scientists said.
“This was a healing environment,” two experts not involved in the research wrote in an editorial that accompanied the study, published Monday in JAMA Internal Medicine. “Hyperbaric oxygen treatment does not work, but the ritual of intervention does.”
They are also advertised for a variety of off-label uses not covered by insurance, including treatment of autism, stroke and migraines. Each session typically costs $200 to $400.
Last year the FDA warned consumers that unproven claims about hyperbaric oxygen therapy abound on the Internet.
Its use to treat concussions was championed by Dr. Paul Harch, a hyperbaric medicine specialist at Louisiana State University. He reported that his patients were seeing improvements after getting treatments that tripled the amount of oxygen delivered to the brain.
Those who also suffered from things like post-traumatic stress disorder, depression, sleep problems and anxiety — all of which were common among the study subjects — saw those conditions improve as well. In some ways, that was not surprising, because their symptoms often overlap with those of concussions.
But the gains came in sharp contrast to the lack of any meaningful progress in the group that never entered a chamber.
Dr. Scott Miller, the lead author of the study and an internist at the Uniformed Service University of the Health Sciences, said his team is continuing to follow the service members. If their improvements persist, researchers will be left to figure out which elements of the treatment ritual — as opposed to the treatment itself — are responsible.
"Shams are not benign," he said. "We're continuing to try to find what works."
A fourth, more extensive controlled trial is underway and on track to be completed next year.
"We're not planning any further studies beyond what's already ongoing," Miller said.