Introduction: Therapeutic hypnosis appears to offer psychological and physiological benefits in various medical fields, but despite increasing interest, its value for anaesthesia remains inconclusive.

Methods: We searched for studies of any design in which hypnosis was used for any intervention requiring the presence of an anaesthetist, alone or in combination with any type of anaesthesia, on children and adults. Meta-analyses using random-effects models were stratified on hypnosis timing, when three or more randomised controlled trials reported on a similar outcome. Additional analyses were performed adding data derived from non-randomised controlled studies. The primary outcome was the use of hypnotics and opioids during the intervention. Secondary outcomes included all outcomes related to pain, anxiety or adverse events.

Results: We identified 142 studies that included 9238 patients (8319 adults, 919 children). Pre-intervention hypnosis decreased post-intervention visual analogue scale pain score (mean difference -0.88 cm, 95%CI -1.72 to -0.05) and anxiety (standardised mean difference -0.76, 95%CI -1.14 to -0.38). Per-intervention hypnosis decreased visual analogue scale pain intensity during the intervention (mean difference -1.14 cm, 95%CI -1.86 to -0.41) without impacting on post-intervention pain; decreased post-intervention anxiety (standardised mean difference -0.44, 95%CI -0.75 to -0.13); and lowered the risk of postoperative nausea and vomiting (risk ratio 0.43, 95%CI 0.25-0.74). Adding non-randomised controlled studies did not alter these results substantially. Evidence of the impact of pre- or per-intervention hypnosis on other outcomes, or of post-intervention hypnosis on any outcome, was lacking.

Discussion: Hypnosis may help reduce anxiety, alleviate pain during and after a procedure and lower the incidence of postoperative nausea and vomiting. However, despite the inclusion of more than 9000 patients in studies examining the use of hypnosis for anaesthesia, its impact on most outcomes remains unknown.