Hypnotherapy for insomnia: A systematic review and meta-analysis of randomized controlled trials

Highlights

• This is the first systematic study on the efficacy of hypnosis for insomnia.

• Methodological quality of the studies included was found to be largely low.

• The therapeutic components and adverse events of hypnotherapy remain unclear.

• Hypnosis improves insomnia but the generalizability of the results was doubtful.

• Research with improved methodology and better adverse events monitoring is demanded.

Abstract

Objective

To examine the efficacy and safety of hypnotherapy for insomnia as compared to placebo, pharmacological or non-pharmacological intervention, or no treatment.

Methods

A systematic search on major electronic databases was conducted up until March 2014. Inclusion criteria are: (1) randomized controlled trials (RCTs) or quasi-RCTs; (2) intervention targeted at improving sleep; (3) hypnosis as an intervention; and (4) English language articles. Sleep diary variable is the primary outcome measure.

Results

Six RCTs of hypnotherapy and seven on autogenic training or guided imagery, comprising 502 subjects, were included. Eleven of the 13 studies had low methodological quality, as indicated by a modified Jadad score below 3, and high risks of bias in blinding and design of the control interventions. No adverse events related to hypnosis were reported, though seldom investigated. Meta-analyses found hypnotherapy significantly shortened sleep latency compared to waitlist (standardized mean difference, SMD = −0.88, 95% confidence interval (CI): −1.56, −0.19, P = 0.01, I² = 15%), but no difference compared to sham intervention (SMD: −1.08, 95% CI: −3.15, 0.09, P = 0.31, I² = 90%). Similar results were found for autogenic training or guided imagery (SMD with waitlist = −1.16, 95% CI: −1.92, −0.40, P = 0.003, I² = 0%; SMD with sham intervention = −0.50, 95% CI: −1.19, 0.19, P = 0.15, I² = 0%).

Conclusions

Generalizability of the positive results is doubtful due to the relatively small sample size and methodological limitations. Future studies with larger sample size and better study design and methodology are called for.

Introduction

Insomnia is a highly prevalent, persistent, and disturbing condition worldwide. As a symptom, its prevalence varies from 10% to as high as 40% among studies; when diagnostic criteria are applied, the prevalence remains between 10 and 20%.¹ Not only does insomnia pose significant impact on the individuals’ daytime functioning, it is also widely associated with health problems such as major depression, anxiety disorders, substance abuse, suicide, decreased immune functioning and cardiovascular disease.² Mainstream treatments of insomnia include pharmacological and cognitive-behavioral therapy (CBT). Although effective pharmacological treatments for insomnia are available, their use is limited by concerns over their long-term efficacy, side effects and the potential for abuse or dependence.³ While the long-term efficacy of CBT for insomnia is well supported by empirical evidence,⁴ its application is limited by the likelihood to drop out resulting from the side effects of sleep restriction.⁵ In addition, a recent randomized controlled trial (RCT) has found a 59.5% treatment response rate, meaning that CBT may not be applicable for everyone.⁴ Faced with the limitations of the currently available treatments, complementary and alternative medicine is gaining popularity for improving sleep.⁶ A national survey in the U.S. showed that 4.5% of non-institutionalized adults reported using some form of complementary and alternative medicine to treat insomnia or trouble sleeping in the preceding year, among which 39.1% have used mind-body therapies such as hypnosis.⁷ With emphasis on the use of relaxation, hypnosis is pleasant, faster and easier to learn. It can be self-practiced conveniently in any place and time after training, and therefore reducing the dependence on the therapist and enhancing self-control and perception of self-efficacy.⁸

Chronic insomnia has been hypothesized as a state of hyperarousal, expressed as peripheral and central activations, with symptoms and behavioral manifestations such as excessive worry and autonomic symptoms.⁹ A recent review provides consistent findings in support of the hyperarousal theory in chronic insomnia, including increased heart rate, cortisol secretion, body temperature, whole-body and global brain metabolism as well as beta electroencephalographic activity.¹⁰

Hypnotherapy is considered potentially beneficial to insomnia patients as it offers self-practicable methods in managing anxiety, enhancing deep relaxation, and reducing cognitive over-activity and sympathetic arousal associated with anxious pre-occupations through relaxation and imagery.¹¹ Hypnosis has been applied in many medical and psychological conditions, such as various pain conditions, depression, and anxiety,¹² which are all closely associated with insomnia. The efficacy of hypnosis for these disorders is well supported. For example, previous meta-analyses showed that hypnosis has a small to medium effect size for the treatment of pain conditions,¹³ depressive symptoms,¹⁴ and psychosomatic disorders.¹⁵ The British Psychological Society asserted that hypnotherapy is as effective as relaxation training for insomnia.¹⁶

In addition to case reports of hypnosis in treating insomnia,10, 17 there have also been RCTs. Two review papers were published,18, 19 providing theoretical framework and preliminary summary to support the efficacy of hypnosis for insomnia. However, no systematic review has been performed. In light of the long history of use, theoretical support for hypnotherapy in treating insomnia, and the public’s demand on more viable alternative interventions for insomnia, we performed a systematic review and meta-analysis to provide a clear and reliable summary of the evidence regarding the efficacy and safety of hypnosis for insomnia.