It seems strange that a drug of abuse, psilocybin, could be used to treat dependence of another drug, nicotine– but this study explores the potential efficacy of this unconventional therapy. Previous research from the 1950s-1970s showed that hallucinogens may be effective in treating drug dependence, such as alcoholism and opioid dependence. A more recent study, performed with the rigor and controls of modern research, has shown the potential for psilocybin to reduce anxiety and depression in those with advanced stage cancer and that these effects lasted well beyond the time of administration. Typical smoking cessation pharmacotherapy result in modest 6-month success rates (often less than 35%), so this study aimed to test the safety and potential efficacy of using psilocybin for smoking cessation.
This study recruited 15 subjects to participate in a 15-week open label pilot trial. Inclusion criteria was smoking at least 10 cigarettes a day, having several unsuccessful past attempts at quitting, and current desire to quite. Every participant went to a weekly cognitive behavioral therapy session for the first 4 weeks and then received a moderate dose (20 mg/ 70 kg) of psilocybin at week 5. Participants also set a target quit date (TQD) for the day they were receiving their first dose of psilocybin. Two additional psilocybin administrations were offered at weeks 7 and 13 with optional higher dosing (30 mg/ 70 kg). These administrations were intended to be additional quit opportunities for those who did not remain abstinent after the first administration. Participants met with staff to reflect each week throughout the study as well as after each psilocybin session. They also received quick phone calls from the staff for 2 weeks after the TQD for encouragement to quit.
Many measures were taken to ensure safety. Blood pressure and heart rate were monitored throughout the psilocybin sessions, and a physician and rescue medications were available in case adverse events occurred. At each session, participants were encouraged to lie on a couch, wear an eye mask, and listen to a music program. The staff provided interpersonal support to manage any effects of the drug. There were no clinically significant adverse effects experienced by any of the participants during any of the sessions, although blood pressure and heart rate were slightly elevated.
Outcomes measured in this study included exhaled carbon monoxide and urinary cotinine levels, both of which are biological indicators of smoking. Psychological aspects of smoking and dependence were measured through various tests and questionnaires, including the smoking timeline follow-back assessment, Fagerström Test for Cigarette Dependence, Questionnaire on Smoking Urges, Smoking Abstinence Self-Efficacy scale, and Wisconsin Smoking Withdrawal Scale. The effects of psilocybin were monitored through other questionnaires including the Visual Effects Questionnaire, a post-session headache interview, Mysticism Scale, States of Consciousness Questionnaire, Persisting Effects Questionnaire, and a questionnaire to measure if patients believed psilocybin had been efficacious in aiding smoking cessation.
12 out 15 (80%) of the participants demonstrated abstinence at the 6 month follow up via questionnaires and carbon monoxide/ cotinine levels (although 3 of the participants reported self-corrected lapses). There were signifiant reductions in self-reported daily smoking, carbon monoxide and cotinine levels, as well as significant differences in Smoking Abstinence Self-Efficacy confidence, Smoking Abstinence Self-Efficacy temptation, Questionnaire on Smoking Urges, and Wisconsin Smoking Withdrawal Scale scores. Reasons people claimed psilocybin helped with quitting included changing their outlook toward the future, strengthening their confidence in quitting, and changing life priorities and values. Only 1 participant reported that psilocybin did not aid smoking cessation. Participants who managed to quit were able to quit after only the first administration.
More studies, particularly controlled studies, would have to be conducted to support the efficacy of psilocybin in smoking cessation, but this study did show that it can be safe and feasible as an adjunct to smoking cessation treatment. This is promising when considering that current therapies involve many adverse effects and have lower quit rates. It is interesting that only one or a few doses needed to be administered in order for psilocybin to have a lasting effect on smoking cessation. It is also interesting to consider what the mechanism may be as it is not clear from this study how psilocybin can potentially affect smoking habits. While psilocybin is a Schedule I drug, there is no clear evidence that it engenders addiction and this study administered it in a safe and controlled manner.
Johnson MW, et al. Pilot study of the 5-HT2AR agonist psilocybin in the treatment of tobacco addiction. J Psychopharmacol. 2014; 28(11):983-92