Researchers have been saying for decades that psilocybin — the main psychoactive ingredient in magic mushrooms — can help treat anxiety and depression. Now, two new studies seem to bolster their claims.

The studies, published Thursday in the Journal of Psychotherapy, reportedly show that a “single psychedelic experience could produce profound and enduring mental health benefits.”

The research, conducted by doctors at New York University and Johns Hopkins University, focused on cancer patients who were experiencing a range of psychological problems after successfully undergoing chemotherapy and other conventional treatments for their conditions.

The NYU researchers wrote that giving the patients controlled doses of psilocybin “produced immediate, substantial, and sustained improvements in anxiety and depression and led to decreases in cancer-related demoralization and hopelessness, improved spiritual well being, and increased quality of life.”

The studies build on previous work with cancer patients at the universities, and add to a large body of research dating back to the 1950s indicating that hallucinogens, including LSD, can be valuable for psychotherapy.

Prof. David Nutt, a revered neuropsychopharmacologist at Imperial College London, who did not participate in the studies but authored an editorial that accompanied their publication, called them “the most rigorous controlled trials” to date using psilocybin.

Nutt, a longtime advocate of psychedelic-assisted therapy, also said the studies laid to rest any concerns about the safety of magic mushrooms, which were outlawed in the U.S. in 1970. Psilocybin remains a Schedule I controlled substance, meaning federal authorities believe it has no medical value and a high potential for abuse.

“There was no evidence of psilocybin being harmful enough to be controlled when it was banned, and since then, it has continued to be used safely by millions of young people worldwide with a very low incidence of problems,” Nutt wrote.

The NYU study involved 29 patients who were treated over a six-month period, while the Johns Hopkins researchers gave psilocybin to 51 patients over the same timeframe. None of them experienced serious side effects.

Dr. Craig Blinderman, director of the adult palliative care service at the Columbia University Medical Center and New York-Presbyterian Hospital,told the Associated Press the studies show “very impressive results,” but more research is still needed.

Despite consistent evidence that psilocybin is relatively safe compared to other drugs, researchers at both universities warned people not to experiment with it at home. The studies, they cautioned, involved precise doses of psilocybin administered in a controlled setting with physicians present to monitor the patients and guide their experience.