Mind-altering compounds, such as LSD and psilocybin, stirred controversy in the 1960s. As the counter-culture's psychedelic drugs of choice, the widespread use - and abuse - of hallucinogens prompted tougher anti-drug laws.
That also led to a crackdown on clinical studies of the drugs' complex psychological effects.
However, now the U.S. Food and Drug Administration (FDA) has begun to approve limited research into the potential benefits of psychedelic drugs.
Fresh look
No one is more aware of the stigma attached to psychedelics than Rick Doblin, director of the Multi-Disciplinary Association for Psychedelic Studies (MAPS), a drug development firm that funds FDA-approved clinical trials to examine the potential therapeutic uses of psychedelics.
Doblin says the virtual blackout on research that resulted from aggressive federal drug-control policies in the 1960s finally began to ease in 1990, when new regulators at the FDA decided to take a fresh look at psychedelic drugs.
"They decided they would put science over politics and permit research to go forward," he says. "They were willing to acknowledge that these drugs could be administered in a safe-enough context and that there were promising hints of potential benefits and therapeutic uses. Today, there is more psychedelics research taking place than in the last 40 years."
'Ecstasy' helps recall lost memories
One especially active focus of FDA-approved research has involved MDMA - also known as "Ecstasy."
This potent drug is being studied for its potential therapeutic value for sex-abuse victims and combat veterans suffering from chronic, treatment-resistant post-traumatic stress disorder, or PTSD.
Dr. Michael Mithoefer conducted small FDA-approved clinical trials using MDMA and a placebo. He found the drug - when administered in tandem with psychotherapy - helped patients recall traumatic, but long-buried, memories.
"So what we are seeing with MDMA is it seems to allow people to access the trauma, revisit it with a sense that they are not going to be overwhelmed by the fear and anxiety," Mithoefer says, "but at the same time, helps them to overcome whatever emotional numbing they have so they can connect with the emotions, and process the trauma that way."
Two months after their sessions, 83 percent of the subjects who had been given MDMA had significantly fewer PTSD symptoms, or none at all, while 25 percent of subjects in the placebo group showed such improvements. And the benefits lasted more than three years.
Psychedelic drug possibilities
Other psychedelic drugs also show clinical possibilities. For example, University of San Diego researcher Thomas Brown found that a plant-derived psychedelic, called ibogaine can help reduce withdrawal symptoms and cravings in heroine and methadone addicts.
In another study, UCLA researchers reported that the psychedelic compound, psilocybin - found naturally in certain mushrooms - can ease end-of-life anxiety in cancer patients when administered in carefully controlled and monitored sessions.
The word "psychedelic" literally means "mind manifesting." Psychologist Neal Goldsmith authored "Psychedelic Healing," a survey of the many uses for these powerful psychoactive drugs. According to Goldsmith, some psychedelics have proved helpful in couples therapy, and as aids to meditation and other spiritual practices.
"From my perspective, psychedelics bring us awareness that our deepest, truest nature is healthy, whole, perfect, loving," he says. "So it's a very interesting time now, where we are rediscovering our spiritual natures through a scientific method."
Spiritual link
The link between psychedelics and spirituality has been of special interest to Roland Griffiths, a behavioral biologist at Johns Hopkins University.
In two FDA-approved experiments, his research team gave large doses of psilocybin to carefully-screened volunteers. They were placed in a pleasant, home-like laboratory environment, outfitted with eyeshades to avoid distractions, and given headphones through which they could listen to music.
Griffiths wanted to see if the psilocybin could induce spiritual experiences similar to those mystics have reported as a natural result of meditation and prayer. Griffiths says that in almost every case the psychedelic triggered a profound sense of spirituality.
"That is, an experience of the interconnectedness of all peoples, an experience that is permeated with a sense of the 'sacred,' an experience of heart-opening or infinite love, a collapse of time and space and, perhaps most importantly, a sense that the experience is more real and more true than everyday waking consciousness."
Not for everyone
Some people don't respond well to psychedelic drugs, according to Griffiths.
Fear and confusion, coupled with physical discomfort, dizziness or nausea can create an unpleasant, even terrifying experience.
Griffiths doesn't advocate the unsupervised use of these powerful drugs.
But he believes, in the hands of properly trained professionals, psychedelics are a valuable and still largely unexplored tool for healing and understanding the human mind.