The hippie adage, "Turn on, tune in, drop out," now comes with a modern addendum: "Get federal funding."

January marked the 50th anniversary of the Human Be-In, the historic drug policy protest that attracted tens of thousands of people to San Francisco in 1967 and served as the catalyst for the Summer of Love. It also spurred the radical ascension of psychedelic science research into mainstream medicine.

The Human Be-In sparked a cultural paradigm shift unrivaled since World War II, and despite a conservative backlash and decades-long prohibition, psychedelics are inexorably moving from the Polo Field of Golden Gate Park into the therapist's office.

Federal research dollars now flow into studies that support giving marijuana and MDMA, or ecstasy, to post-traumatic stress disorder sufferers, and the hallucinogens LSD and psilocybin to cancer patients with depression and anxiety. The drugs work, modern studies show.

"These ideas became so embedded in our own culture, we don't even sometimes remember that they were once radical ideas pushed forward by a group of young people who gathered in a neighborhood," says Haight-Ashbury resident Annie Oak, founder of feminist psychedelics nonprofit Women's Visionary Congress.

For thousands of years, humans have used plant-derived drugs to alter their consciousness for therapy and spirituality. In the modern era, the potent hallucinogen LSD was first created by Swiss chemist Albert Hoffman in 1938 and became a candidate for psychotherapeutic uses by 1950.

Researchers used LSD to treat depression and alcoholism until 1962, as it became the focus of more than 1,000 published studies and cultural buzz. Then the Federal Drug Administration began restricting such research, and as use spread, especially among young people, California lawmakers feared for public safety. On Oct. 6, 1966, the state banned LSD, sparking several protests, including the Be-In.

President Richard Nixon's war on drugs vilified psychedelics and cannabis. By 1970, federal officials ranked those drugs among the most dangerous, and research nearly stopped. Marijuana and most psychedelics remain federally illegal to this day, but researchers have persevered.

Much of the progress they have made is the result of more than 30 years of work by the Multidisciplinary Association for Psychedelic Studies, or MAPS, a Bay Area nonprofit founded by Rick Doblin in 1986. Doblin has a doctorate in public policy from Harvard's Kennedy School of Government, where he wrote his dissertation on the regulation of the medical uses of psychedelics and marijuana.

Since the Be-In, "marijuana has gone from being a heavily demonized drug used by rebellious youth to a medicine with one of the largest growing demographics being elderly people," says Doblin.

Psychedelics have taken a similar path.

"Research was virtually eliminated across the world, and now (psychedelics) are being investigated as tools used in scientific research for therapeutic uses, a catalyst of spirituality, art and creativity, acceptance of death, and we are now facing their legitimization and acceptance as medical tools," Doblin adds.

Since about 2000, private and international teams have revamped the study of psychedelics, mostly with private funding. California and seven other states have legalized cannabis for adult use, generating tens of millions of tax dollars earmarked for research that otherwise would not be performed.

Doblin thinks psychedelics will follow the route of cannabis — first accepted medicinally, then more broadly.

Today, the first U.S. government-approved human trials assessing psychedelics in tandem with psychotherapy treatment are yielding positive results. Psychedelics can alter brain function just long enough to gain lasting, new perspectives on crippling fears and traumas, according to researchers.

For most of these studies, participants with a chronic, intractable psychological issue, such as PTSD, are given a placebo or controlled dose of a psychedelic such as MDMA, also known as ecstasy. Patients then take part in a guided therapy session. The results so far show unprecedented success and safety across the board.

Through the work of MAPS, MDMA could be made a legal medicine, in tandem with therapy to treat severe post-traumatic stress and anxiety, by 2020. The group has also sponsored other breakthrough studies with results pointing to the potential of MDMA, LSD, psilocybin and other drugs to help a variety of severe, treatment-resistant mental health conditions.

"The future of psychedelics in our society is bright — a thousand points of light," Doblin says. "The integration of psychedelics into health care practices could not come at a better time for America, when healing and understanding are desperately needed."

Bill McCarthy, founder of the Unity Foundation and co-producer of the Human Be-In 50th Anniversary celebration, believes the current political climate makes events like the Be-In more relevant than ever.

"If we take that long view, bringing it back to '67 and forward until now, and we see all the changes, movements, breakthroughs," he says, "how can we be afraid?"

April M. Short is a freelance writer who focuses on health and drug policy.

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To learn more about psychedelic drug research: www.sfchronicle.com/summer-of-love