To anyone who lived through the 1960s, the proposition that psychedelic drugs might have a positive contribution to make to our mental health must sound absurd. Along with hallucinogens like mescaline and psilocybin (that is, magic mushrooms), LSD was often blamed for bad trips that sent people to the psych ward. These drugs could make you crazy.

So how is it possible that, 50 years later, researchers working at institutions such as New York University, Johns Hopkins, UCLA and Imperial College in London are discovering that, when administered in a supportive therapeutic setting, psychedelics can actually make you sane? Or that they may have profound things to teach us about how the mind works, and why it sometimes fails to work?

Recent trials of psilocybin, a close pharmacological cousin to LSD, have demonstrated that a single guided psychedelic session can alleviate depression when drugs like Prozac have failed; can help alcoholics and smokers to break the grip of a lifelong habit; and can help cancer patients deal with their “existential distress” at the prospect of dying. At the same time, studies imaging the brains of people on psychedelics have opened a new window onto the study of consciousness, as well as the nature of the self and spiritual experience. The hoary ‘60s platitude that psychedelics would help unlock the secrets of consciousness may turn out not to be so preposterous after all.

The value of psychedelic therapy was first recognized nearly 70 years ago, only to be forgotten when what had been a promising era of research ran headlong into a nationwide moral panic about LSD, beginning around 1965. With a powerful assist from Timothy Leary, the flamboyant Harvard psychology professor, psychedelics had escaped the laboratory, falling into the eager arms of the counterculture. Yet in the decade before that there had been 1,000 published studies of LSD, involving 40,000 experimental subjects, and no fewer than six international conferences devoted to what many in the psychiatric community regarded as a wonder drug.

Compared with other psychoactive compounds, these powerful and mysterious molecules were regarded as safe—it’s virtually impossible to overdose on a psychedelic—and nonaddictive. Rats in a cage presented with a lever to administer drugs like cocaine and heroin will press it repeatedly, unto death. LSD? That lever they press only once.