A new study has found promising evidence that the smoking cessation drug varenicline (Chantix/Champix) may help people with cannabis use disorder (CUD) reduce their cannabis consumption.

Cannabis use disorder is a growing global problem, partly due to recent legalization in several countries and U.S. states, and no medications have yet been approved for its treatment. CUD is characterized by continued cannabis use despite “clinically significant impairment,” such as neglect of important social, occupational, or recreational activities, and persistent use despite physical or psychological problems related to cannabis. Cannabis use is also associated with psychosis, sleep disturbances, withdrawal symptoms, mood disorders, and anxiety. Varenicline is an effective medication for smoking cessation.

In this study, conducted at the Medical University of South Carolina and published in the journal Addiction, researchers tested whether varenicline could help treat cannabis use disorder.

The results showed that varenicline helped men reduce cannabis use, but not women. (Notably, varenicline is equally effective for smoking cessation in both sexes.) The study included 174 adults with CUD who used cannabis at least three days per week. Participants were randomly assigned to receive either varenicline (1 mg twice daily) or a placebo for 12 weeks. They also attended weekly brief medical visits to support adherence to both the medication and the treatment plan.

Men in the varenicline group used cannabis less frequently per week than those receiving placebo. Specifically, men taking varenicline reported an average of 7.9 cannabis use sessions per week during the study and 5.7 sessions in the week following the study, compared with more than 12 weekly sessions in the placebo group. Men treated with varenicline also used cannabis on an average of 3.8 days per week, compared with 4.7 days per week among men receiving placebo.

In contrast, women who received varenicline did not differ from women taking placebo in their cannabis use. Women in the varenicline group reported just over 10 sessions per week on average, compared with 9.2 weekly sessions in the placebo group (which decreased to 8.2 in the week after the study). Women taking varenicline used cannabis an average of 4.9 days per week, compared with 3.6 days per week among women receiving placebo. Women treated with varenicline also showed higher levels of withdrawal symptoms and craving, as well as higher anxiety, than any other group.

This difference may be related to the fact that women taking varenicline reported lower adherence to the treatment regimen than women receiving placebo.