Even some Republicans, a group that has traditionally opposed the liberalization of drug laws, are starting to come around. Last month, the former Texas governor Rick Perry, citing the high rates of suicide among war veterans, called on his state’s legislators to support a Democratic-sponsored bill that would establish a psilocybin study for patients with PTSD.

“We’ve had 50 years of government propaganda around these substances, and thanks to the research and a grass-roots movement, that narrative is changing,” said Kevin Matthews, a psilocybin advocate who led Denver’s successful ballot measure.

Decades in the Wilderness

Long before Nancy Reagan warned the nation to just say no to drugs and President Richard Nixon supposedly pronounced Timothy Leary “the most dangerous man in America,” researchers like William A. Richards were using psychedelics to help alcoholics go dry and cancer patients cope with end-of-life anxiety.

The drugs were legal, and Dr. Richards, then a psychologist at the Maryland Psychiatric Research Center, was among scores of scientists studying the therapeutic prowess of entheogens, the class of psychoactive substances that humans have used for millenniums. Even years later, Dr. Richards and other researchers say, many early volunteers called the psychedelic sessions the most important and meaningful experiences of their lives.

But as the drugs left the lab in the 1960s and were embraced by the counterculture movement, the country’s political establishment reacted with alarm. By the time the Drug Enforcement Administration issued its emergency ban on MDMA in 1985, funding for psychedelic research had largely disappeared.

“We were learning so much, and then it all came to an end,” said Dr. Richards, 80, and now a researcher at Johns Hopkins University School of Medicine.

These days, the Center for Psychedelic and Consciousness Research at Johns Hopkins, created two years ago with $17 million in private funding, is studying, among other things, psilocybin for smoking cessation and the treatment of depression associated with Alzheimer’s as well as more spiritual explorations involving religious clergy.