Q: As with medical marijuana, is there any health benefit to be found in psychedelic drugs?

A: After more than 30 years in which psychedelics were considered dangerous remnants of the 1960s, the drugs have begun to make a comeback as potential remedies for a host of tough-to-treat maladies.

Pilot studies and clinical trials of LSD, psilocybin, ketamine and MDMA have shown that the drugs, often in combination with talk therapy, can be given safely and may help people dealing with opiate and tobacco addiction, alcoholism, anxiety, depression and post-traumatic stress disorder, or PTSD.

This potential is not surprising to many researchers. A generation of scientists and practitioners had used psychedelics successfully with thousands of patients until the research was banned in 1970, after the drugs were embraced by an exploding counterculture that seemed to threaten the status quo.

In the panicked reaction, psychedelics were listed along with heroin in the highest rungs of prohibition. Ironically, this failed to stop recreational use but it shut the science down cold. As one researcher put it, “It was as if psychedelic drugs had become undiscovered.”

But a small cadre of psychiatrists and researchers, risking careers and reputations, pushed to bring psychedelics back to the lab and the clinic.

Their persistence paid off. Beginning in the 1990s, the Food and Drug Administration approved the first human clinical studies of psychedelic drugs in a quarter of a century. By 2004, the first FDA-approved trial of the medicinal use of a psychedelic drug — a trial of MDMA-assisted therapy for PTSD — was underway.

Research in the 1950s made it clear that serotonin affected mood and thoughts, and that LSD and other psychedelic drugs worked by somehow altering the way the brain processes serotonin. Because psychedelic molecules are physically similar to serotonin, the two fit into the same receptors in the brain, like two keys in a lock.

The specifics of how psychedelics interact with serotonin receptors to produce a mind-altering trip remain mysterious and disputed.

The most interesting clues have come from studies using functional magnetic resonance imaging, or fMRI, a technology that depends on the magnetic properties of blood flow to create pictures of a brain in operation.

In 2012, researchers at Imperial College London published results of a study in which they injected volunteers with psilocybin and then observed their brains via fMRI.

Given the psychedelic experience’s well-known assault on the senses — flashing visual patterns, intense colors, enhanced sounds, overwhelming visions and emotions — the researchers expected to see increased brain activity.

Instead, their screens registered decreased activity, which seemed like a mistake until it was confirmed by another scan and correlated with the participants’ reports: The larger the decrease in brain activity, the more intense the experience.

The researchers noted two intriguing connections with other studies: A brain on psilocybin bore a striking resemblance to the brain of an experienced meditator during deep meditation.

And the areas of the brain with decreased activity caused by psilocybin were the same regions that showed chronically increased activity in people with clinical depression.

“We’re motivated to think of the potential of this drug more seriously through the brain imaging results,” said Robin Carhart-Harris, lead researcher in the Imperial College study. “Regions which are reliably overactive in depression are deactivated by psilocybin . . . and that fits with the anecdotal reports of users of psychedelic drugs who feel a renewed ease with life after an experience, less burdened by everyday stresses.”

– Tom Shroder, The Washington Post