A rigorous new study finds that a single dose of LSD can ease anxiety and depression for months.

The study involved 198 adults with generalized anxiety disorder , or GAD, a disabling form of anxiety that affects about 1 in 10 people over the course of a year.

Participants who got lower doses of LSD (25 or 50 micrograms) did no better than those who got a placebo. But people who received higher doses (100 or 200 micrograms) responded quickly, a team reports in the Journal of the American Medical Association.

"By the next day, they were showing strong improvements," says Dr. David Feifel of Kadima Neuropsychiatry Institute in San Diego, one of the 22 centers that participated in the study. "And those improvements held out all the way to the end of the study, which was 12 weeks."

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