۱- Introduction

۲- Method

۳- Results

۴- Discussion

References

Abstract

The current meta-analysis aimed to quantify the effectiveness of hypnosis for reducing pain and identify factors that influence efficacy. Six major databases were systematically searched for trials comparing hypnotic inductions with no-intervention control conditions on pain ratings, threshold and tolerance using experimentally-evoked pain models in healthy participants. Eighty-five eligible studies (primarily crossover trials) were identified, consisting of 3632 participants (hypnosis nö=ö۲۸۹۲, control nö=ö۲۶۴۶). Random effects meta-analysis found analgesic effects of hypnosis for all pain outcomes (gö=ö۰٫۵۴-۰٫۷۶, p’s<.001). Efficacy was strongly influenced by hypnotic suggestibility and use of direct analgesic suggestion. Specifically, optimal pain relief was obtained for hypnosis with direct analgesic suggestion administered to high and medium suggestibles, who respectively demonstrated 42% (pö<ö.۰۰۱) and 29% (pö<ö.۰۰۱) clinically meaningful reductions in pain. Minimal benefits were found for low suggestibles. These findings suggest that hypnotic intervention can deliver meaningful pain relief for most people and therefore may be an effective and safe alternative to pharmaceutical intervention. High quality clinical data is, however, needed to establish generalisability in chronic pain populations.

Introduction

Pain affects up to 1.5 billion adults worldwide (Yaqub, 2015) and has a substantial negative impact on quality of life. In addition to becoming one of the leading causes of years lived with disability (GBD Causes of Death Collaborators, 2017), pain also incurs a massive economic burden. Pain-related health care and lost productivity incur annual costs of up to $635 billion in the US alone (Gaskin and Richard, 2012), greater than that of heart disease, cancer or diabetes. Increasing concern over the side effects, addictive properties and costs of opioid medication has led to an urgent need to identify non-pharmacological interventions for pain that are effective, safe, and inexpensive. One popular psychological intervention for pain management is hypnosis, which typically involves relaxation, focused attention and targeted verbal suggestion to alter perceptual experience and behaviour (Jensen and Patterson, 2014). Hypnosis is easily administered, has few or no side effects, and is inexpensive if delivered in a pre-recorded format (e.g., audio recording) that does not require the presence of a practitioner (Jensen et al., 2015). Recent research has indicated that hypnotic suggestion produces altered activity in key regions of the brain involved in pain regulation, including the anterior cingulate, prefrontal and insular cortices (Del Casale et al., 2015), and this could provide a basis for possible analgesic effects. Exaggerated claims of hypnotic analgesia have, however, created scepticism over its efficacy (Larkin, 1999), and a rigorous evaluation of controlled trials is needed to properly evaluate and quantify its effectiveness for reducing pain. A recent meta-analysis of 14 trials of people with chronic pain (Adachi et al., 2014) concluded that hypnosis was effective for managing pain. However, this conclusion was based primarily on a subset of 4 studies comparing hypnosis with standard care (d = .60, CI95[0.03, 1.17]) that was largely unreplicated in other subset comparisons.