Some studies on ketamine and addiction, however, suggest that its antidepressant effect wears off over time, and participants may need repeated infusions. This is a potential problem because the drug itself has the potential to become a drug of abuse and overdoses can, in rare cases, be fatal.
Researchers who are enthusiastic about psilocybin say its longer, more intense psychedelic experience make it a more long-lasting therapeutic. It generally requires just a single session or sometimes several sessions to be effective, provided it’s integrated with psychotherapy or some other form of counseling.
“People have greater mental flexibility following psilocybin,” said Matthew Johnson, a psychologist at Johns Hopkins who leads the smoking trial. “That increase in openness might be a permanent change that can help in overcoming addiction.”
An uncertain future
Although psilocybin remains illegal under federal drug laws, some cities, including Denver, and Santa Cruz, Calif., have decriminalized it. Oregon, in November 2020, voted to become the first state to legalize it for medical use.
Psilocybin is considered safer than ketamine and is not habit-forming, but it does have its downsides. The greatest risks may come from a person who uses the drug alone and wanders into traffic or other dangerous situations while high. Even in the supervised setting of a research laboratory, users often experience side effects, such as vomiting or loss of coordination, and the trip itself can produce anxiety, pain, or even a psychotic break.
“One of the big challenges of these treatments is that the effects are somewhat unpredictable,” Dr. Bogenschutz said.
The California Institute of Integral Studies is one of the best known organizations offering a certificate program to train future therapists working with psychedelics, but since psilocybin-assisted therapy remains illegal, an underground treatment market has popped up around the country.