Abstract: 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. 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.

Plain-language summary: We found 14 studies comparing hypnotherapy with other approaches to help people stop smoking (including brief advice, or more intensive stop-smoking counselling), or no treatment. Overall, 1926 people were included. Studies lasted at least six months. The studies varied greatly in terms of the treatments they compared, so it was difficult to combine their results. We searched for evidence up to 18 July 2018. When we combined the results of six studies (with a total of 957 people) there was no evidence that hypnotherapy helped people quit smoking more than behavioural interventions, such as counselling, when delivered over the same amount of time. There was also no evidence that there was a difference between hypnotherapy and longer counselling programmes when we combined results from two studies (269 people). One study compared hypnotherapy with no treatment and found an effect in favour of hypnotherapy, but the study was small (40 people) and had issues with its methods, which means we cannot be certain about this finding. Most of the studies did not say if they also evaluated the safety of hypnotherapy. Five studies looked at adding hypnotherapy to existing treatments and found an effect, but the studies were at high risk of bias and there were large, unexplained differences in their findings. One study that compared hypnotherapy and relaxation found no difference in side effects. The evidence in this review ranges from low to very low certainty, as there was not enough information and many of the studies had issues with their designs. There is no clear evidence that hypnotherapy is better than other approaches in helping people to stop smoking. If a benefit is present, current evidence suggests the benefit is small at most. Larger, high-quality studies are needed.