"Depression continues to affect a large proportion of the population, many of whom do not respond to conventional treatments," said Dr. Scott Krakower, a psychiatrist who reviewed the study.
"Although this was a small study, it does offer hope for new, unconventional treatments, to help those who are battling with severe depression," said Krakower, who is chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, N.Y.
The new trial included 12 people with moderate to severe depression who had been resistant to standard treatment. All of the patients were given the compound psilocybin, found in hallucinogenic mushrooms.
Three months after treatment, seven patients had reduced symptoms of depression, according to a team led by Dr. Robin Carhart-Harris of Imperial College London, in England.
There were no serious side effects, the study authors said in the report published May 17 in The Lancet Psychiatry.
Carhart-Harris' team stressed that no strong conclusions can be made from the findings -- only that further research is warranted.
About 1 in 5 patients with depression does not respond to treatments such as antidepressants or cognitive behavioral therapy, the study authors noted.
"This is the first time that psilocybin has been investigated as a potential treatment for major depression," Carhart-Harris said in a journal news release.
"The results are encouraging, and we now need larger trials to understand whether the effects we saw in this study translate into long-term benefits, and to study how psilocybin compares to other current treatments," he said.
How might the drug work to ease depression?
"Previous animal and human brain imaging studies have suggested that psilocybin may have effects similar to other antidepressant treatments," explained study senior author David Nutt, also of Imperial College London.
"Psilocybin targets the serotonin receptors in the brain," he said, "just as most antidepressants do, but it has a very different chemical structure to currently available antidepressants and acts faster than traditional antidepressants."
However, Krakower stressed that caution must be taken with such a powerful drug.
"Psilocybin is still a potent psychedelic compound and can have unwanted side effects," he said. "Patients should interpret these results with caution until more studies are conducted."
Another mental health expert agreed.
"Anyone reading of this study should be cautioned to not use this drug on themselves," said Dr. Alan Manevitz, a clinical psychiatrist with Lenox Hill Hospital in New York City.
He said the study also had some flaws, most notably its small size and the fact that patients had "expectations" of benefit that might have skewed the results.
Furthermore, the need to watch over the patient, "for hours after treatment may make this an impractical drug to clinically use and further research into dosages is required," Manevitz said.
But he noted that this isn't the first time psilocybin has been thought of as medicine.
"Psilocybin has been considered for the use for easing the psychological suffering associated with end-stage cancer," he explained. "Preliminary results indicate that low doses of psilocybin can improve the mood and anxiety of patients with advanced cancer, with the effects lasting two weeks to six months."
The U.S. National Institute of Mental Health has more on depression.
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