This mantra becomes even more central on the day they take their first psilocybin. After four sessions of CBT, the volunteers smoke what is meant to be their last cigarette. For some this is the night before, for others it’s literally just before the session. “We've had people smoke in the parking lot right before they come in here,” Johnson tells me.

Then, it’s time for the drug. Albert Garcia-Romeu, a post-doctoral fellow at Johns Hopkins, who ‘guides’ the volunteers through the CBT and the psilocybin sessions, describes how it works: “We have them self-administer the capsule. We take their cell phone. We take their shoes. We give them some slippers. We want them to relax into the day and feel almost like they're in a spa. They don't have to go to work. They don't have to do their normal day-to-day thing.”

“We practice before. Give them our hand so that they have the support if they need it,” explains Mary Cosimano, another of the guides who has been working in the field for more than 15 years. “We tell them, ‘We're here for you as much as you like’.”

“Once the drug effect starts to kick in, we encourage them just to lie down,” continues Garcia-Romeu. “They put on headphones. They cover their eyes. We have them just lay back and watch and wait.”