A Systematic Review of the Use of St. John's Wort for Smoking Cessation in Adults.

St. John’s wort (SJW) has been researched and clinically used for treating various psychiatric disorders, including depression. Few clinical trials have studied its use in smoking cessation. This systematic review provides comprehensive evidence of the studies conducted to date. Five databases were searched for randomized controlled trials (RCTs) that evaluated the effectiveness of SJW for smoking cessation in adults. The trials included the use of SJW alone, or along with nicotine replacement therapy, chromium, or behavioral therapies. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to report this systematic review. Overall, four RCTs met the eligibility criteria, and the risk of bias analysis was conducted using the Cochrane criteria. Abstinence, along with other physical symptoms, were measured as outcomes at the end of the follow-up period. Studies reported variable abstinence rates and a decrease in cravings at the end of 12-14 weeks. However, there was minimal to no difference reported between the intervention and placebo groups in all of the clinical trials. One of the studies reported minimal physical side effects. Overall, SJW was well tolerated. Quality analysis of the included studies showed low concerns in two studies while the other two studies showed high concerns in the risk of bias judgment. More clinical trials with larger sample sizes should be conducted in the future to evaluate the effectiveness of the use of SJW for smoking cessation.