The drug trials that inspired Walker were the work of MAPS, a nonprofit research organization whose name stands for Multidisciplinary Association for Psychedelic Studies. It’s one of a small handful of organizations worldwide trying to establish scientific evidence that psychedelic drugs have therapeutic value.

In the study looking at how MDMA could treat PTSD, the drug was given in conjunction with talk therapy. Patients lay down in a therapist's office and listened to soothing music with headphones, wearing eyeshades. They had the option of talking about what they were experiencing, and received counseling before and afterwards to integrate what happened to them while on the drug into their everyday lives. According to MAPS, 83 percent of the 19 people treated in a recent group had breakthroughs in this MDMA-assisted therapy and showed significant improvement in their PTSD symptoms.

"A lot of the demonization of drugs as evil in all walks of American life has really calmed down."

"The MDMA allowed me to be my very, very, very best self, and I got to take care of my most broken self with my best self," says Rachel Hope, a sexual-abuse survivor who participated in the study. MAPS’ results from this study were encouraging enough to the FDA that it was able to expand its efforts into what’s known in drug-trial parlance as "Phase 2 studies." It’s now doing the same study with four new groups of patients in South Carolina, Colorado, Israel, and Vancouver.

In addition to the MDMA-to-treat-PTSD study, MAPS has also studied how LSD can help soothe anxiety in people with terminal illnesses, and in March received approval to study the effects of marijuana to alleviate PTSD. The latter study will be one of only two government-approved medical marijuana trials ever conducted.

Similarly to MAPS, the Santa Fe-based scientific research group the Heffter Research Institute has been collaborating with scientists at UCLA, Johns Hopkins, and NYU to study the therapeutic applications for psilocybin, the active ingredient in hallucinogenic mushrooms. In one study, published in 2011, it investigated how the drug might be used to make terminally ill cancer patients feel less anxious and depressed, and reported that of 11 patients given the drug, 30 percent reported an elevated mood that lasted long after the drug wore off. Now, Heffter scientists are looking at how psilocybin might help cure alcoholism and get people to quit smoking.

In many ways, this research isn’t new. Besides the thousands of years of indigenous peoples’ ritual use of mind-altering plants like ayahuasca and peyote, there was some modern scientific exploration of these kinds of substances, too. Before it was criminalized in 1968, LSD was being used by some doctors as an experimental method for treating alcoholism and anxiety. MDMA, prior to being outlawed in 1985, was used by hundreds of psychotherapists in the United States to treat a variety of phobias, addiction, trauma, and even relationship problems. In an interview with psychiatrist Julie Holland, author of the book Ecstasy: The Complete Guide, one of these therapists recalled: "When it came to, for instance, couples therapy, it was a remarkable catalyst."