Many people, then, choose to go it alone, or with a friend as a kind of trip-sitter. They might get their information on doses and substances (or just read first-person accounts) from forums like Reddit, Bluelight, and Erowid, or from books such as Julian Vayne’s Getting Higher, Michael Pollan’s How to Change Your Mind, and Stanislav Grof’s Realms of the Human Unconscious.

That’s exactly what Cameron, a consultant in London, does when he suffers burnout or has some kind of emotional problem that won’t shift. The 30-year-old had read about clinical trials in the media; now he looks up doses on forums and sets an intention. Sometimes he goes solo, sometimes he drops a dose with a friend. He’s used LSD and mushrooms, but for a breakup that had been bothering him for 18 months, he took MDMA. “I don’t usually come to any conclusion during the trip, but it tends to crystallize afterwards,” he told me. “In this instance, I was able to understand why my ex-girlfriend did what she did, and to empathize. Afterwards, I went from having no contact with her to us being quite close friends.”