RESUMO
INTRODUCTION: Acceptance and commitment therapy (ACT) is increasingly being studied as a treatment for smoking cessation. However, its immediate, short-, and long-term effects have rarely been reviewed. METHODS: This systematic review aimed to evaluate the effectiveness of immediate, short-, medium-, and long-term smoking cessation rates in ACT and comparators at less than 3-month, 3 to 4-month, 6-, and 12-month follow-ups. Randomized controlled trials (RCTs) were searched in eight databases until April 20, 2023. We assessed the quality of RCTs and the certainty of evidence of outcomes. RESULTS: Nineteen RCTs involving 7885 smokers across six countries were included. The majority (72.81%) of RCTs were graded as low risk across six domains. For complete-case outcomes, meta-analyses were conducted, and the results revealed a significant effect in favor of ACT [risk ratio: 1.70-1.80 at <3-month, 3 to 4-month, and 6 months follow-up] compared with comparators. For outcomes using missing data management, meta-analyses found an overall effect in favor of ACT, but a significant effect was found at 3 to 4-months only. However, 12-month follow-ups revealed no significant reduction in smoking cessation for both outcomes. Moderate and substantial heterogeneities were found among four meta-analyses that may lead to inaccurate estimates of effects. The certainty of evidence of all outcomes was rated as low and very low. CONCLUSION: ACT may be an effective intervention for smoking cessation with immediate, short-term, and medium-term effects. Caution must be applied in the interpretation of the results due to the limited trials and low certainty of evidence. IMPLICATION: ACT can be implemented adjuvant to the usual treatment for smoking cessation. Additional RCTs with follow-up data using biochemically verified measures in non-US countries are warranted.