The therapy was lysergic acid diethylamide (LSD). By the mid-sixties, the man voted Hollywood’s Most Attractive was one of an estimated 40,000 people who had used it in an attempt to heal their brains, whether to unravel long-repressed trauma or to overcome addictions.

Today, of course, thanks to the proselytizing of Timothy Leary and its degradation into hippie culture’s “acid,” a cheap street drug, it and many other hallucinogens are illegal and believed to have, like heroin and cocaine, a high potential for abuse and what the U.S. Drug Enforcement Administration calls “no currently accepted medical use.”

But are hallucinogenic drugs really of no value to medicine? Flash forward to 2013: With North America awash in powerful pharmaceuticals that are perfectly legal, yet addictive and widely abused, some mental-health professionals are making a case for reviving banned mind-altering substances, arguing that they can enable insight, empathy and long-term recovery from trauma.

Forty-five years after LSD became the first of them to be prohibited, the psychedelics and their chemical cousins are making a comeback, launching what is being called a revolution in treating, and perhaps curing, some of the most refractory disorders of the human brain.

At the Harbor-UCLA Medical Center in Los Angeles, psilocybin – the active ingredient in magic mushrooms – is being used to reduce anxiety in end-stage cancer patients. At the University of Ottawa, a researcher is studying ketamine, which has put many a raver into the infamous “K-hole,” as an alternative to shock therapy for severely depressed patients.

In New Zealand, the hallucinogenic African shrub iboga has been reclassified as a promising treatment for opiate addiction, and in England, a tidal wave of research, much of it using up-to-the-minute brain-scanning techniques, is showing how once-reviled street drugs can be used to treat everything from obsessive-compulsive disorder to chain smoking.

The work exciting the most interest, however, involves something that has long been a conundrum for medical science: post-traumatic stress disorder (PTSD).

With hundreds of thousands of Canadians believed to be suffering from PTSD – more soldiers commit suicide after serving in Iraq and Afghanistan than were killed there in combat – a highly effective treatment may be available in the form of a mind-expanding drug known to chemists as 3,4-methylenedioxy-N-methylamphetamine (MDMA) and to the public at large as ecstasy.