The efficacy and safety of hypnotic techniques in somatic medicine, known as medical hypnosis, have not been supported to date by adequate scientific evidence.
We systematically reviewed meta-analyses of randomized controlled trials (RCTs) of medical hypnosis. Relevant publications (January 2005 to June 2015) were sought in the Cochrane databases CDSR and DARE, and in PubMed. Meta-analyses involving at least 400 patients were included in the present analysis. Their methodological quality was assessed with AMSTAR (A Measurement Tool to Assess Systematic Reviews). An additional search was carried out in the CENTRAL and PubMed databases for RCTs of waking suggestion (therapeutic suggestion without formal trance induction) in somatic medicine.
Out of the 391 publications retrieved, five were reports of meta-analyses that met our inclusion criteria. One of these meta-analyses was of high methodological quality; three were of moderate quality, and one was of poor quality. Hypnosis was superior to controls with respect to the reduction of pain and emotional stress during medical interventions (34 RCTs, 2597 patients) as well as the reduction of irritable bowel symptoms (8 RCTs, 464 patients). Two meta-analyses revealed no differences between hypnosis and control treatment with respect to the side effects and safety of treatment. The effect size of hypnosis on emotional stress during medical interventions was low in one meta-analysis, moderate in one, and high in one. The effect size on pain during medical interventions was low. Five RCTs indicated that waking suggestion is effective in medical procedures.
Medical hypnosis is a safe and effective complementary technique for use in medical procedures and in the treatment of irritable bowel syndrome. Waking suggestions can be a component of effective doctor–patient communication in routine clinical situations.
Hypnosis for purposes of medical treatment goes back a long way. The British Medical Association endorsed the use of hypnosis in somatic medicine in 1955, on the basis of case reports and series backed up by expert consensus, and the American Medical Association followed suit in 1958 (1, 2). Whether robust evidence exists for the efficacy and safety of hypnosis in somatic medicine in the era of evidence-based medicine (EBM) (3) remains to be clarified. Because systematic reviews with quantitative analysis (meta-analyses) of randomized controlled trials provide the highest level of evidence in EBM (3), we decided to carry out a systematic review of meta-analyses on medical hypnosis.
The aims of this article are as follows:
To define the various forms of hypnosisTo describe the requirements that have to be fulfilled before therapeutic hypnosis can be carried out
To provide a historical overview of the use of hypnosis in medicine and the assessment of its efficacy
To identify the indications for medical hypnosis supported by robust evidenceTo present the evidence for use of positive suggestions as a component of effective doctor– patient communication.
The term “hypnosis” is used to mean both an altered state of consciousness (synonym: hypnotic trance) and the procedure by which this state is induced (4). During a hypnotic trance physiological, cognitive, and affective processes as well as behavior can be modified. A hypnotic state and hypnotic phenomena can be induced by another person (therapist) or alone (self-hypnosis). The subjective experience of hypnosis is characterized by a high degree of authenticity (experienced as real) and involuntariness (“it happens by itself”) (4).
Hypnosis can be distinguished from other states of consciousness such as normal wakefulness, sleep, deep relaxation, or meditation by means of electroencephalography (EEG) and imaging modalities (4). A hypnotic trance is characterized by a number of physiological and mental reactions, e.g., altered perception of time, selective amnesia, regression to a younger age (retrieval of memories or experiences from an earlier developmental stage), a marked inward focus, and heightened suggestibility, i.e., a stronger reaction to suggestions (4). In clinical situations associated with high affective participation of the patient, such as emergencies, diagnostic and therapeutic interventions, or communication of a serious diagnosis, hypnotic phenomena may occur spontaneously (e1, e2).
Suggestions work via verbal and nonverbal signals that correspond to internal expectations and have a powerful effect on mental and involuntary somatic processes. For example, cutaneous perfusion or the flow of saliva is not amenable to influence by a deliberate intellectual action, but can be affected by a suggestion, e.g., a picture or a story. In general use the word “suggestion” tends to imply manipulation, but in hypnosis it should be understood as meaning a proposal, an offer of options (“I suggest”). In contrast to the widespread preconceptions, hypnosis is not authoritarian, passive, and centered around the therapist, but a resource- and solution-oriented method in which the focus is on the patient’s own potentials (4).
Depending on the goals, various applications of hypnotic techniques can be distinguished (4):
Medical hypnosis Alleviation of somatic symptoms Reduction of mental stress during medical treatment Amelioration of disordered physiological/biochemical parameters Facilitation of physiological/biochemical healing processes Hypnotic communication Waking suggestions (suggestions without trance induction) Suggestions with the patient under general anesthesia Use of findings from hypnotherapy for effective doctor–patient communication Hypnotherapy (psychotherapy with the patient in a trance) Improvement of problem management by giving the patient access to their own resources Facilitation of changes in behavior Restructuring (minimization, reinforcement, new conditioning) of cognitive–affective patterns Restructuring of emotionally stressful events and sensations Reintegration of non-accessible (dissociated) feelings Experimental hypnosis Basic research on somatic sensations (e.g., pain), emotions, and states of consciousness Stage hypnosis Demonstration of hypnotic phenomena to entertain an audienceThe perception of hypnosis as an authoritarian, manipulative technique, nourished particularly by its use in stage shows, represents the greatest barrier to the (re)integration of hypnosis into medical treatment.
A session of medical hypnosis generally lasts between 20 and 50 min and can be divided into various phases (4):
- Verification of the indication; explanation (correction of inappropriate anxiety or false expectations); definition of goal(s)
Consolidation Therapeutic suggestions Reorientation, posthypnotic suggestions DiscussionIntegration into daily routine: use of an audio file at home; behavioral exercises (e.g., exposure training); possibly learning of self-hypnosis techniques.
A selection of broadcasts (mostly in German) publicly available on the internet can be found in eBox 1.
In Israel and Sweden, hypnosis may be carried out only by physicians and psychologists who have received appropriate training. In Germany, from the legal point of view, anyone can offer hypnosis for non-medical reasons. Treatment of illness by means of hypnosis requires a license to perform procedures for the purpose of healing (medical and psychological psychotherapists, child and adolescent psychotherapists, naturopaths) (e3). Medical hypnosis can be carried out by physicians of all patient-related specialties in the framework of basic psychosomatic care. An invoice for relaxation hypnosis according to the official German schedules for physicians’ fees (Uniform Value Scale, Einheitlicher Bewertungsmaßstab) can be submitted only by persons who possess a qualification in basic psychosomatic care and have successfully completed a course in hypnosis comprising two units of 16 hours each (e4). Most medical and psychological psychotherapists and child and adolescent psychotherapists learn the techniques of hypnotherapy as a supplementary qualification. As a rule hypnotherapists are also trained in other methods of psychotherapy.
Details of the history of hypnosis and assessment of its efficacy prior to the introduction of evidence-based medicine (EBM) are provided in eBox 2.
Owing to their unconventional approach, hypnosis techniques attracted the attention of both orthodox physicians and the general public at an early stage. The scientific basis of hypnotic procedures was investigated as early as the 18 th century.
The theory and techniques of “animal magnetism,” put forward by the Viennese physician Franz Anton Mesmer, are viewed as the precursor of modern hypnosis. Mesmer failed in his attempt to have animal magnetism accredited by the Académie des Sciences in Paris in 1784 (e5). The scientific committee appointed by King Louis XVI refuted the theory of magnetism and attributed Mesmer’s successful treatments to psychological mechanisms, namely the “arousal of powers of imagination and of imitation” (e6). The concept of magnetism persisted, however, and came to be adopted by a number of physicians. The English surgeon James Esdaile (1808–1859), working in India, carried out 345 major operations (amputations of arm, leg, breast, and penis, as well as excision of tumors) using the technique of “mesmerism” and recorded not only good analgesia but also low mortality (e7). The British physician John Elliotson (1791–1868) became professor at the University of London in 1831. Under pressure from the journal Lancet, which rejected his practice of animal magnetism, he resigned his post in 1838. From 1843 to 1856 he published a journal called The Zoist, dedicated exclusively to animal magnetism. However, this technique rapidly receded into the background with the introduction of ether and chloroform anesthesia in 1846/47 (e3).
The Scottish ophthalmologist Braid developed the theory of monoideism, whereby concentration on a single thought by means of optic fixation was held to lead to a neurologically conditioned state of sleep. This physiological explanation of hypnotic phenomena helped “hypnotism” attain recognition by physicians at a time when medicine was developing along scientific lines (e3). In 1891 the British Medical Association (BMA) commissioned a group of physicians to investigate hypnotism. After due appraisal the expert committee concluded that hypnotism was effective in the treatment of pain, sleep disorders, and functional symptoms. At its annual conference in 1892 the BMA unanimously recommended the therapeutic application of hypnosis (e8).
With the increasing importance of evidence-based medicine (EBM) in the 20 th and 21 st centuries, advocates and practitioners of clinical hypnosis came to see the necessity of controlled trials and synthesis of the findings in systematic reviews. The first German-language systematic review and meta-analysis of the efficacy of hypnosis was published in 2002 (e9). An expert report on evaluation of hypnotherapy as a psychotherapeutic technique according to the criteria of the German Scientific Advisory Committee on Psychotherapy (Wissenschaftlicher Beirat Psychotherapie) (§ 11, Psychotherapy Act) was produced in 2003 (e3). The Scientific Advisory Committee on Psychotherapy concluded that hypnotherapy can be considered a scientifically valid technique for the treatment, in adults, of mental and social factors in somatic diseases and of addiction and abuse (smoking cessation and methadone withdrawal) (ICD-10 F54, F10, F11) (e10).
This review was conducted according to the recommendations of the Cochrane Collaboration for systematic reviews of previously published reviews and the recommendations of the Joanna Briggs Institute for umbrella reviews (6).
The Cochrane databases CDSR and DARE and PubMed were searched for systematic reviews (SRs) published in the period January 2005 to June 2015. The following search terms were used: “review,” “meta-analysis,” and “hypnosis”. We searched PubMed with “((“hypnosis”[MeSH] OR “hypnosis, dental”[MeSH]) AND (“meta-Analysis” [Publication Type] OR “review” [Publication Type])) OR ((hypnosis OR hypnotherap * ) AND (meta-analy * OR metaanaly * ))”. Moreover, the reference lists of the SRs identified were inspected for further SRs. With regard to waking suggestions we searched the databases CENTRAL and PubMed for randomized controlled trials (RCTs) using the terms “suggestion” [MeSH] and “hypnotic suggestion”. Finally, for all topics we asked experts in medical hypnosis about SRs.
The following conditions regarding study type, indications, setting, and study population had to be fulfilled:
Study type: We included SRs with meta-analysis of (quasi-)RCTs on hypnosis as intervention for somatic medical indications. In the event of serial publications by the same group of authors we used the most recent publication. We selected inclusion of at least 400 patients in quantitative analysis (meta-analysis) of the study results as a quantitative criterion of robust evidence (7).
Indications: The endpoints of the meta-analysis had to be somatic symptoms (e.g., pain or nausea) or physiological findings (e.g., bleeding time or airway resistance) and/or mental stress during medical treatments and/or cost-related data (e.g., operating time, legth of hospital stay, or drug consumption). We excluded meta-analyses of RCTs on psychiatric and psychotherapeutic indications (e.g., anxiety disorders, depressive disorders, addiction/abuse, or behavioral disorders) and meta-analyses of RCTs on various diseases (e.g., psychosomatic illnesses) in which no subgroup analyses were conducted for individual diseases.
Setting and study population: No restrictions were imposed with regard to setting, age, or country.
The methodological quality of the meta-analyses was verified using AMSTAR (A Measurement Tool to Assess Systematic Reviews) (8). AMSTAR scores of 0–4 were classified as low, 5–8 as intermediate, and 9–11 as high methodological quality (9).
The following characteristics of the meta-analyses were extracted independently by two of the authors (WH, MH) and discrepancies were resolved by consensus: