By 1970, acid and related compounds had become part of a dangerous menu of street drugs, and governments cracked down, bringing research to a near halt. Other mind-altering recreational drugs, like psilocybin (the ingredient in magic mushrooms) and MDMA, or ecstasy, also landed on the lists of banned substances.

The revival of interest began in the early 1990s, when the Food and Drug Administration agreed to approve careful, well-designed, ethically vetted studies of psychedelics for the first time in decades. The Heffter Institute and the Multidisciplinary Association for Psychedelic Studies , or MAPS, a nonprofit funded by an assortment of wealthy donors, financed projects in the United States and abroad. MAPS collaborated with Dr. Hofmann and Alexander Shulgin, a former Dow chemist who discovered the effects of ecstasy, and with his wife, Ann, experimented with scores of hallucinogens.

Experiments using ecstasy and LSD, for end-of-life care, were underway by the mid-2000s. Soon, therapists began conducting trials of ecstasy for post-traumatic stress, with promising results. One of the most influential scientific reports appeared in 2006: a test of the effects of a strong dose of psilocybin on healthy adults. In that study, a team led by Roland Griffiths at Johns Hopkins found that the volunteers “rated the psilocybin experience as having substantial personal meaning and spiritual significance and attributed to the experience sustained positive changes in attitudes and behavior.”

At least as important as the findings, which were exploratory, was the source, Johns Hopkins, with all its reputational weight, and no history of institutional bias toward alternative treatments. “I got interested through meditation in altered states of consciousness, and I came into this field with no ax to grind,” said Dr. Griffiths, the director of the new center.

By late 2018, the Johns Hopkins group had reported promising results using psilocybin for depression, nicotine addiction and cancer-related distress. Others around the world, including Dr. David Nutt at Imperial College London, were producing similar results.

Mr. Ferriss, who organized half the $17 million in commitments and contributed more than $2 million of his own for the new Johns Hopkins center, said he approached wealthy friends who he knew had an interest in mental health. The new venture, he said he told them, “truly has the chance to bend the arc of history, and I’ve spent nearly five years looking at and testing options in this space to find the right bet. Would you have any interest in discussing?”