INTRODUCTION Allen Carr's (AC) method is a pharmacotherapy-free approach to quit smoking that is delivered through seminars, online courses, or in the form of a book. It has gained popularity, but its effectiveness remains controversial due to a lack of scientific evidence. This systematic review aims to provide an updated overview of the current evidence on the effectiveness of the AC method.

METHODS We conducted a systematic literature review of all epidemiological studies evaluating the effectiveness of the AC method for smoking cessation, published in PubMed/MEDLINE and Embase up to March 2023.

RESULTS Among 34 original studies identified through the literature search, six met the inclusion criteria. These studies were published between 2006 and 2020, with sample sizes ranging from 92 to 620 participants. Of the six studies, two did not have a comparison group while four, including two randomized control led trials (RCT), had a comparison group. The included studies showed cessation rates for people who attended the seminars from 19% to 51%. An observational study found an odds ratio (OR) of abstinence for those attending AC single-session seminars of 6.52 (95% confidence interval, CI: 3.10-13.72) compared with controls with no treatment. One RCT found higher quit rates for AC single-session seminars compared with the online Irish National service (OR=2.26; 95% CI: 1.22-4.21). Another RCT reported no significant difference between AC single-session seminars and a specialist stopsmoking service. One single study on patients with head and neck disorders analyzed the effectiveness of reading the AC book, showing no significant results.

CONCLUSIONS The AC seminar may be an effective intervention for smoking cessation. This approach deserves further RCTs with large sample sizes to strengthen the evidence. Scant data are available on the effectiveness of reading the AC book.