Hypnotherapy for smoking cessation.
Barnes J., McRobbie H., Dong CY., Walker N., Hartmann-Boyce J.
BACKGROUND: Hypnotherapy is widely promoted as a method for aiding smoking cessation. It is intended to act on underlying impulses to weaken the desire to smoke, or strengthen the will to stop. OBJECTIVES: To evaluate the effect and safety of hypnotherapy for smoking cessation. SEARCH METHODS: For this update we searched the Cochrane Tobacco Addiction Group Specialized Register, and trial registries (ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform), using the terms "smoking cessation" and "hypnotherapy" or "hypnosis", with no restrictions on language or publication date. The most recent search was performed on 18 July 2018. SELECTION CRITERIA: We considered randomized controlled trials that recruited people who smoked and implemented a hypnotherapy intervention for smoking cessation compared with no treatment, or with any other therapeutic interventions. Trials were required to report smoking cessation rates at least six months after the beginning of treatment. Study eligibility was determined by at least two review authors, independently. DATA COLLECTION AND ANALYSIS: At least two review authors independently extracted data on participant characteristics, the type and duration of hypnotherapy, the nature of the control group, smoking status, method of randomization, and completeness of follow-up. These authors also independently assessed the quality of the included studies. In undertaking this work, we used standard methodological procedures expected by Cochrane.The main outcome measure was abstinence from smoking after at least six months' follow-up. We used the most rigorous definition of abstinence in each trial, and biochemically validated abstinence rates where available. Those lost to follow-up were considered to still be smoking. We summarized effects as risk ratios (RRs) and 95% confidence intervals (CIs). Where possible, we performed meta-analysis using a fixed-effect model. We also noted any adverse events reported. MAIN RESULTS: We included three new trials in this update, which brings the total to 14 included studies that compared hypnotherapy with 22 different control interventions. The studies included a total of 1926 participants. Studies were diverse and a single meta-analysis was not possible. We judged only one study to be at low risk of bias overall; we judged 10 studies to be at high risk of bias and three at unclear risk. Studies did not provide reliable evidence of a greater benefit from hypnotherapy compared with other interventions or no treatment for smoking cessation. Most individual studies did not find statistically significant differences in quit rates after six months or longer, and studies that did detect differences typically had methodological limitations.Pooling small groups of relatively comparable studies did not provide reliable evidence for a specific effect of hypnotherapy relative to controls. There was low certainty evidence, limited by imprecision and risk of bias, that showed no statistically significant difference between hypnotherapy and attention-matched behavioural treatments (RR 1.21, 95% CI 0.91 to 1.61; I2 = 36%; 6 studies, 957 participants). Results were similarly imprecise, and also limited by risk of bias, when comparing hypnotherapy to intensive behavioural interventions (not matched for contact time) (RR 0.93, 95% CI 0.47 to 1.82; I2 = 0%; 2 studies, 211 participants; very low certainty evidence). Results from one small study (40 participants) detected a statistically significant benefit of hypnotherapy compared to no intervention (RR 19.00, 95% CI 1.18 to 305.88), but this evidence was judged to be of very low certainty due to high risk of bias and imprecision. No significant differences were detected in comparisons of hypnotherapy with brief behavioural interventions (RR 0.98, 95% CI 0.57 to 1.69; I² = 0%; 2 studies, 269 participants), rapid/focused smoking (RR 1.00, 95% CI 0.43 to 2.33; I2 = 65%; 2 studies, 54 participants), and pharmacotherapies (RR 1.68, 95% CI 0.88 to 3.20; I2 = 5%; 2 studies, 197 participants). When hypnotherapy was evaluated as an adjunct to other treatments, the pooled result from five studies showed a statistically significant benefit in favour of hypnotherapy (RR 2.10, 95% CI 1.31 to 3.35; I² = 62%; 224 participants); however, this result should be interpreted with caution due to the high risk of bias across studies (four had a high risk or bias, one had an unclear risk), and substantial statistical heterogeneity.Most studies did not provide information on whether data specifically relating to adverse events were collected, and whether or not any adverse events occurred. One study that did collect such data did not find a statistically significant difference in the adverse event 'index' between hypnotherapy and relaxation. AUTHORS' CONCLUSIONS: There is insufficient evidence to determine whether hypnotherapy is more effective for smoking cessation than other forms of behavioural support or unassisted quitting. If a benefit is present, current evidence suggests the benefit is small at most. There is very little evidence on whether hypnotherapy causes adverse effects, but the existing data show no evidence that it does. Further large, high-quality randomized controlled trials, and more comprehensive assessments of safety, are needed on this topic.