Now, thanks to a few high-profile efforts, some researchers are starting to study them again. But there's a problem.
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And the environment in which you take these drugs can have a big impact on your experience.
Psychedelics as medicine
Despite numerous studies in the 1960s suggesting potential benefits of drugs like LSD in psychiatric treatment, the Controlled Substances Act of 1970 declared that drugs like LSD, ecstasy (MDMA), psilocybin, and marijuana had no accepted medical use, and effectively banned research on them until the 1990s.
Scientists have since studied the therapeutic use of psychedelics for the treatment of everything from cluster headaches to depression and addiction. Nevertheless, these studies have been small and researchers say it's tough to come to any definitive conclusions based solely on them.
But two organizations are revamping some of this research, Langlitz writes.
The nonprofit Multidisciplinary Association for Psychedelic Studies (MAPS) in California is conducting clinical trials of MDMA, or ecstasy, as a treatment for post-traumatic stress disorder (PTSD), while a New Mexico-based nonprofit Heffter Research Institute is investigating the use of psilocybin in the treatment of anxiety and depression in cancer patients, as well as its use in treating alcoholism and smoking addiction.
The primary tool for these studies is the placebo-controlled trial, a study in which participants receive either the drug or an inactive substance (placebo). All other conditions are kept the same, the idea being that only the drug's effects are being measured.
The problem with placebo-controlled trials
The problem is, the experience of taking a psychedelic drug can vary widely depending on the context in which you take it, Langlitz writes.
The Harvard psychologist Timothy Leary, who experimented heavily with LSD, called this concept "set and setting." Leary argued that the "character" of a psychedelic experience is determined primarily by the user's character, expectations, and intentions (the "set"), as well as by the social and physical surroundings where the user took the drug (the "setting").
But most placebo-controlled studies don't take this into account. And simply measuring the effect of these drugs compared with a placebo is missing some crucial components of the user's experience.
In one study, researchers interviewed nearly 100 current or former ecstasy users about their experiences with the drug, and found that bad experiences were almost always related to the set and setting. Specifically, participants reported that the negative effects they experienced were affected by their mood or expectations, beliefs about the brand of ecstasy they used, and experiences of seeing how it affected their friends.
Another small study from 1975 looked at people who smoked marijuana in a "favorable" or "neutral" environment, and found that their mental set had an big impact on how people reported how the drug was affecting them. The results suggested users' experiences were influenced by their mental state.
And researchers looking into the "Acid House" trend of taking psychoactive drugs at musical concerts in 1980s Britain found that the nature of the music, especially the drumming, "seems instrumental in providing altered states of consciousness."
So, rather than testing psychedelics using the placebo-controlled trial, some researchers have suggested doing "culture-controlled" trials, in which they'd compare the experience of study participants in specific settings. For example, you could compare the experience of teenagers taking ecstasy at a rave with that of the same teens taking the drug in a sterile lab setting.
As more of these drugs make their way into therapeutic research, this approach could be increasingly important.