Clinical hypnosis for chronic pain in adults

  • Protocol
  • Intervention

Authors


Abstract

This is the protocol for a review and there is no abstract. The objectives are as follows:

To determine the efficacy of clinical hypnosis, relative to no treatment, other viable psychological pain treatments (e.g., relaxation, neurofeedback, cognitive therapy), and experimental conditions that are thought to have minimal effects on outcome but that control for therapist attention, time, and patient treatment outcome expectancies, among adults with chronic pain.

Background

Description of the condition

Chronic pain has long been defined as pain that persists beyond the healing time needed to recover from an injury (Patterson 2003), and often for longer than 6 months (Elkins 2007; Keefe 1982). In contrast with acute pain, chronic pain may communicate very little about an associated or underlying disease process (Patterson 2003; also see Chapman 1999). Furthermore, chronic pain is often associated with psychosocial factors (e.g., patient cognitions, coping responses, social and environmental factors) (Patterson 2003; also see Fordyce 1976; Turk 1999).

The International Association for the Study of Pain (IASP) defines chronic pain as "pain without apparent biological value that has persisted beyond the normal tissue healing time (usually taken to be 3 months)" (Harstall 2003). For the purposes of our review, we will use the IASP definition of chronic pain; that is, pain that has persisted beyond 3 months following an initial injury.

Hypnotic analgesia has been utilized as a treatment for chronic and acute pain for a variety of patient populations, including people with serious medical illness (e.g., spinal injury, heart disease) and following dental surgery. Since the mid-1970s, several empirical studies of hypnotic analgesia have provided preliminary evidence for both the effectiveness and efficacy of hypnotic-based interventions (Melis 1991; Melzack 1975; Weinstein 1991). Due to initial evidence that hypnosis alters central processing and appraisal of pain (Rainville 1997), hypnotic analgesia may be a useful treatment for pain-related changes in brain structure, such as the gray matter loss in the para-hippocampal gyrus and frontal cortex, regions related to pain processing (Ramani 2008). In addition to central nervous system (CNS) effects of pain, the cardiovascular and peripheral pain regulatory systems are also altered in chronic pain (Bruehl 1999). More specific to the present review, there is initial evidence that hypnotic treatments for chronic pain can improve people's quality of life, measured either as individual domains or as a composite index, and reduce the economic impact of pain-related disability, including:

  • reductions in mean weekly pain intensity, pain unpleasantness, and pain interference (Jensen 2008);

  • reductions in per-episode pain frequency, duration, and intensity (Simon 2000);

  • per cent of improvement in daily functioning since beginning hypnosis (Simon 2000);

  • reductions in medical care utilization, including number of hospitalizations, emergency room visits, and clinic visits, and total dollar cost of prescriptions filled (Simon 2000).

Description of the intervention

We define hypnosis as a social interaction in which one person, designated the participant, responds to suggestions offered by another person, designated the hypnotist, for experiences involving alterations in sensation, perception, and voluntary action (adapted from Kihlstrom 1985; see also Montgomery 2010). Chronic pain studies that identify the intervention as hypnosis and that meet the above definition will be eligible for inclusion in the present review. A hypnosis treatment usually begins with an 'induction' consisting of one or more initial suggestions for changes in behavior or perception (e.g., for focused attention, relaxation, or both). Clinicians providing hypnotic analgesia treatment usually then follow this induction with specific suggestions for alterations in how pain is viewed or experienced, although the specific suggestions used tend to vary between clinicians (and between research protocols; see Jensen 2006). Hypnotic treatment for chronic pain often, but not always, includes posthypnotic suggestions that are made during the session. These might include the suggestion that the benefits experienced during the session (e.g., a reduction in perceived pain intensity) will last beyond the session, for minutes, hours, or even for days, months, and years, or that the person will be able to create a state of comfort easily after the session after a specific cue (e.g., after taking a deep breath, holding it for a moment, and then letting it go).

To evaluate the benefit of hypnotic analgesia for pain control, Montgomery, DuHamel, and Redd (Montgomery 2000) conducted a meta-analysis of published empirical studies. They concluded that hypnosis reduces pain in most people who score in the moderate to high hypnotic suggestibility range (a relatively stable trait) for both clinical and experimental settings. Hypnotic analgesia for acute pain will not be addressed as part of this review as another Cochrane title exists on this subject as a published protocol (Hallquist 2007). Several reviews have evaluated the effects of hypnotic analgesia (Elkins 2007; Jensen 2006; Patterson 2003; Stoelb 2009) and have found empirical support for the use of hypnosis with chronic pain related to cancer, fibromyalgia, multiple sclerosis, irritable bowel syndrome, headache, temporomandibular disorder, intractable organic pain, non-cardiac chest pain, disability, spinal cord injury, sickle cell disease, back pain, peripheral nerve injury, arthritis, amputation, and trauma. Further research is necessary to evaluate the effects of hypnosis on various diseases (e.g., cancer-related pain), bodily regions (e.g., neck pain), bodily systems (e.g., musculoskeletal pain), and environmental agents (e.g., whiplash-related pain).

How the intervention might work

One of the complicating factors of evaluating the effects of hypnotic analgesia for chronic pain relates to the fundamental difference between acute and chronic pain; the former is the direct result of tissue damage while the latter may persist in the absence of a noxious stimulus due to persistent psychological and neurobiological changes, such as substance P upregulation in peripheral tissue (Millan 1999). While the treatment targets of hypnotic analgesia for acute pain are often narrowly defined (e.g., reduction of pain, medication use, and length of hospitalization), the function of hypnotic analgesia for chronic pain is inherently more complex. Frequently, hypnotic suggestions that are used to treat people with chronic pain are limited to basic suggestions for pain reduction, with the expectation that they will respond as well as people with acute pain (Patterson 2003). Such suggestions "fail to appreciate the multifaceted and complex nature of pain" (Patterson 2003, p. 514), and may contribute to the inconsistent findings in the literature. Hypnotic suggestions for chronic pain should correspond to mechanisms that may cause or exacerbate chronic pain, such as psychological disorders, maladaptive beliefs, somatization or somatosensory amplification, operant conditioning, and avoidance (e.g., of mobility, returning to work) or dependence (e.g., on medication, physicians) (Patterson 2003). The effect of hypnotic analgesia for chronic pain may be strengthened if the intervention targets such mechanisms in addition to pain reduction.

Why it is important to do this review

Previous reviews of hypnotic analgesia for chronic pain (Elkins 2007; Jensen 2006; Patterson 2003; Stoelb 2009) have identified some controlled trials using various criteria and have integrated results among results descriptively; however, to date there has not been a systematic, quantitative review of studies to examine the effects of hypnotic treatments for chronic pain based on established Cochrane procedures. Such a review is needed because: 

  1. prior published reviews were based on limited numbers of controlled trials – there have been several well-designed controlled trials examining the efficacy of hypnotic treatments for chronic pain published since the most recent review; and

  2. Cochrane reviews are based on well-established meta-analytic principles, whereas the approaches represented in published reviews to date were less optimal. 

Further, a Cochrane review of psychological therapies for chronic pain among children and adolescents, including hypnotic analgesia, was developed by Eccleston 2012. Our review will provide new information on adults with chronic pain not covered by other reviews, and based upon well-established meta-analytic principles.

Thus, a Cochrane procedure-based comprehensive review of the efficacy of hypnosis for chronic pain in adults is required.

Objectives

To determine the efficacy of clinical hypnosis, relative to no treatment, other viable psychological pain treatments (e.g., relaxation, neurofeedback, cognitive therapy), and experimental conditions that are thought to have minimal effects on outcome but that control for therapist attention, time, and patient treatment outcome expectancies, among adults with chronic pain.

Methods

Criteria for considering studies for this review

Types of studies

We will include randomized controlled trials (RCTs) of hypnosis for treatment of chronic pain in this review. Both blinded and non-blinded trials will be eligible for inclusion as participants are rarely blinded to treatment condition in hypnosis protocols (see Patterson 1992 for an exception). We will not exclude non-English language articles , and we will seek translation where possible.

Types of participants

Male and female adults (age 18 years or older) with chronic pain, as assessed by medical professionals or by participant self report, will be eligible for inclusion in this review. 

In Moore 2011 the following recommendations were made to those authoring a Cochrane Review:

'...pain severity is crucial in determining analgesic efficacy, which cannot be measured in the absence of pain. In most circumstances, pain of at least moderate severity will be regarded as an important criterion for participant inclusion in studies, and study inclusion in this review. Diagnosis is also an important criterion, since there is usually no prima facie evidence that different painful conditions are equivalent to one another, or that interventions necessarily work to the same extent in different conditions. In most circumstances we will assess the interventions by participant condition or diagnosis in the first instance,' (Moore 2011, p. 6).

We will adhere to these recommendations, with one caveat relating to pain severity. We will examine baseline pain as a potential moderator (e.g., report results for all of the studies as well as separately for those that only allow for moderate or more pain intensity versus those that allow participants to have something less than moderate pain).

Types of interventions

Intervention studies that utilize clinical hypnosis to treat chronic pain conditions will be eligible for inclusion. Hypnosis interventions will focus primarily on posthypnotic pain relief (i.e., reduction in the intensity, frequency, or duration), although mechanisms that may exacerbate chronic pain will also be considered (e.g., endorsement of maladaptive beliefs). 

Comparator interventions may include, but are not limited to, relaxation, cognitive behavioral therapy, biofeedback, neurofeedback, physical therapy, autogenic training, and education. We will assess interventions by frequency, duration, and intensity where possible.

Types of outcome measures

Primary outcomes

The primary outcome of interest will be changes in participant-rated pain intensity. This outcome is typically measured in analgesic trials and is centrally important to the efficacy of hypnosis for chronic pain. 

Initial and outcome pain scores will be evaluated using numerical rating scales (NRS; typically 0-10 or 0-100), visual analog scales (VAS), verbal rating scales (VRS; e.g., the McGill Pain Questionnaire), other commonly employed measures (e.g., Faces Pain Scale, Pain Thermometer), or a combination of these.

David Cella and colleagues (see Revicki 2006) have found that an effect size of d = 0.20 in pain intensity can be perceived by people as beneficial or have the potential to result in changes in treatment. Therefore, overall effect sizes will be reported when possible to allow for clinically meaningful results to be discussed.

Secondary outcomes

Literature has suggested the observation of competing or at least secondary outcome variables, when feasible. Thus, we will analyze competing or secondary outcomes, when appropriate and available, as follows:

  1. observer-rated pain intensity;

  2. medication (analgesic) consumption;

  3. participant-rated functioning (e.g., fatigue, mobility, distress, quality of life);

  4. clinician-rated functioning;

  5. adverse events (e.g., drowsiness, withdrawals);

  6. sleep disturbance;

  7. psychological well-being (e.g., anxiety, depression, maladaptive beliefs);

  8. functional imaging or structural changes;

  9. unexpected benefits (e.g., increased sense of control over pain).

Search methods for identification of studies

See: Cochrane Pain, Palliative and Supportive Care Group methods used in reviews. No language or date restrictions will be applied to the searches.

We will seek relevant clinical trials of hypnosis for chronic pain in four different ways: electronic searches, handsearches, contact with study authors, and contact with hypnosis professional societies.

Electronic searches

Relevant RCTs will be sought via:

  • the Cochrane Central Register of Controlled Trials (CENTRAL) on the Cochrane Library;

  • MEDLINE;

  • PsycINFO;

  • EMBASE. 

The search strategy that will be used to search Medline is shown in Appendix 1. It will be amended, where necessary to search the other databases listed.

We will also search trials registries for details of ongoing trials:

Searching other resources

Reference searches

We will search the reference sections of known review articles on this topic (e.g., Elkins 2007; Jensen 2006; Patterson 2003; Stoelb 2009) and all included studies for further relevant hypnosis intervention research. 

Personal contact

We will contact first authors of all included studies for information regarding relevant unpublished (e.g., studies in press) intervention research.

Hypnosis professional societies

Professional hypnosis societies will be contacted in an effort to uncover further eligible studies:

  1. The American Society of Clinical Hypnosis;

  2. The Australian Society of Hypnosis;

  3. The Society for Clinical and Experimental Hypnosis;

  4. The British Society of Clinical and Academic Hypnosis;

  5. The International Society of Hypnosis;

  6. The American Psychological Association: Division 30, Psychological Hypnosis;

  7. The European Society of Hypnosis;

  8. The Canadian Federation of Clinical Hypnosis.

Data collection and analysis

Selection of studies

Two authors will independently read the titles and abstracts of all studies returned from the searches to determine their eligibility for inclusion in the review. Disagreement among authors will be resolved through discussion and consultation with a third author. Authors will not be blinded to the authors, journals, or results of possible studies.

Data extraction and management

Two authors will independently extract data from each included study using data extraction forms designed specifically for this review. Disagreements among authors will be resolved through discussion and consultation with a third author. If important dates are unclear or unavailable in published studies, first authors of such studies will be contacted to clarify missing information.

We will aim to extract data from each study to include the following, where available:

  1. number of participants in each group;

  2. gender, age, and ethnicity of participants (and other demographics, where available);

  3. study design (including type of control group);

  4. method of randomization;

  5. outcome data (see "Types of outcome measures");

  6. participant withdrawals from intervention;

  7. reasons for participant withdrawal;

  8. description of clinical hypnosis intervention (particularly whether the intervention was termed 'hypnosis');

  9. analysis type (e.g., intention-to-treat (ITT), efficacy analysis);

  10. adverse events associated with hypnotic intervention;

  11. hypnotic suggestibility level.

Assessment of risk of bias in included studies

Two authors will rate the methodological quality of relevant clinical trials using a scale specifically developed by Boutron 2005 to assess the methodological rigor of nonpharmacological RCTs. Such trials depart from typical methodology of pharmacological trials in that treatment providers and participants often cannot be blinded to the treatment conditions and creating a believable placebo condition is often difficult. The scale is composed of 10 items (as well as five subitems not listed here) (Boutron 2005, p. 1237):

  1. was the generation of allocation sequences adequate? (yes; no; unclear);

  2. was the treatment allocation concealed? (yes; no; unclear);

  3. were the details of the intervention administered to each group made available? (yes; no; unclear);

  4. were care providers’ experience or skill in each arm appropriate? (yes; no; unclear);

  5. were participants' adherence assessed quantitatively? (yes; no; unclear);

  6. were participants adequately blinded? (yes; no, because blinding is not feasible; no, although blinding is feasible; unclear);

  7. were care providers or people caring for the participants adequately blinded? (yes; no, because blinding is not feasible; no, although blinding is feasible; unclear);

  8. were outcome assessors adequately blinded to assess the primary outcomes? (yes; no, because blinding is not feasible; no, although blinding is feasible; unclear);

  9. was the follow-up schedule the same in each group? (yes; no; unclear);

  10. were the main outcomes analyzed according to the intention-to-treat principle? (yes; no; unclear).

Measures of treatment effect

We expect that patient-rated pain intensity (the primary outcome of interest) and competing or secondary outcomes will typically be measured on continuous (e.g., (VAS) or quasi-continuous (e.g., Likert-type) scales. This will produce cross-group comparison statistics such as t-tests and F-ratios as well as computation of 95% confidence intervals (CIs) and effect size estimates including standardized mean difference (SMD) (in case of different measures across studies) and weighted mean difference (WMD) (in the case of identical measures across studies). Where possible, we will conduct number needed to treat for an additional beneficial effect (NNTB) and number needed to treat for an additional harmful effect (NNTH) analyses, which provide more clinically relevant data than traditional effect size estimates (McQuay 1997).

Unit of analysis issues

We expect that most studies will include the participant as the unit of randomization. In that regard, we will rate each study with respect to (1) the unit of randomization and (2) the unit of analysis, reporting those studies where the two match.

Dealing with missing data

Two authors will contact authors of articles for additional information (e.g., missing statistics). Review Manager software (RevMan 2011) will be used to analyze all data, and analyses will follow the ITT principle where possible. 

We will make additional efforts to overcome missing data following the recommendations from Moore 2011.

In chronic pain trials withdrawal can be common. The use of last observation carried forward (LOCF) in this circumstance has been criticized (O'Connor 2010) as overestimating the benefits of treatment. Individual-patient data analyses have used the baseline observation carried forward (BOCF) criteria, where failure to tolerate adverse events or withdrawal for any reason constitutes treatment failure, and an inability to be a responder (Moore 2008; Moore 2010; Moore 2010a; Straube 2010) (Moore 2011, p. 12).

Assessment of heterogeneity

We will assess effect size heterogeneity using I2 and Q statistics (Huedo-Medina 2006). We will assess sensitivity analysis and meta-regression techniques using the impact of moderators such as methodological quality, hypnotizability, and sex on effect-size estimates. These analyses may adequately explain possible effect size heterogeneity, but if such exploration cannot account for heterogeneity, we will consider using random-effects models (rather than fixed-effect models) to estimate effect size. Alternatively, we will consider not combining effect-size estimates across studies if effect-size heterogeneity cannot be adequately understood. In either case, the presence of significant effect size heterogeneity suggests that such parameters be interpreted with caution.

Assessment of reporting biases

We will attempt to minimize reporting biases by using a combination of comprehensive search methods, including (1) the inclusion of non-English language articles, (2) searching the reference sections of known review articles and included studies, (3) contacting first authors of included studies for relevant unpublished (e.g., studies in press) intervention research, and (4) contacting professional hypnosis societies for further eligible studies.

Data synthesis

As stated above, we will use a fixed-effect model to estimate effect size; however, if sensitivity analysis and meta-regression cannot account for effect-size heterogeneity, we will consider a random-effects model.

Subgroup analysis and investigation of heterogeneity

We will analyze subgroups to determine whether the efficacy of clinical hypnosis is moderated by age, sex, ethnicity, diagnosis, or other demographic variables. If possible, we will analyze hypnotic suggestibility scores on standard hypnotizability measures (e.g., Stanford Hypnotic Susceptibility Scale, Form C; Weitzenhoffer 1962) as potential moderators of hypnotic analgesic effects.

Sensitivity analysis

We will examine the impact of methodological quality on estimates of treatment effects using sensitivity analysis (Juni 2001; Verhagen 2001). Specifically, we will plot effect-size estimates against quality components to ascertain whether treatment effects vary as a function of particular aspects of methodological quality. Additionally, where possible, we will utilize meta-regression models that incorporate quality components as predictors of effect-size estimates. We will not use methodological quality of studies to weight treatment-effect analyses (Juni 2001). 

Appendices

Appendix 1. MEDLINE search strategy

Search criteria will use a combination of controlled vocabulary and free text terms based on the following search strategy for MEDLINE (via OVID):

1. hypnosis.tw. 
2. exp Hypnosis/ 
3. (imagery or hypnotherapy or mesmerism or autohypnosis or "autogenic training" or suggestion or hypno*).tw. 
4. or/1-3 
5. exp Pain/ 
6. pain.tw. 
7. exp Analgesia/ 
8. analges*.tw. 
9. or/5-8 
10. randomized controlled trial.pt. 
11. controlled clinical trial.pt. 
12. randomized.ab. 
13. placebo.ab. 
14. drug therapy.fs. 
15. randomly.ab. 
16. trial.ab. 
17. groups.ab. 
18. 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 
19. exp animals/ not humans.sh. 
20. 18 not 19 
21. 4 and 9 and 20

Note that the third clause of this search is drawn from the Cochrane Highly Sensitive Search Strategy for identifying randomized trials in MEDLINE: sensitivity-maximizing version (2008 revision); OVID format.

(This can be found in Section 6.4.11 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011)).

Contributions of authors

MA: design and coordinate the review, design search strategies, undertake searches, organize retrieval of papers, analyze and interpret data (supporting analyst), and write the review.

MH: consult on design of search strategies and statistical analysis, undertake searches, extract data from papers, and write the review.

MJ: extract data from papers, enter data into RevMan for analysis, analyze and interpret data (supporting analyst), write the review, and perform previous work that was the foundation of the current study.

DP: screen retrieved papers against inclusion criteria, write to authors for additional information about papers, obtain and screen unpublished studies, analyze and interpret data (supporting analyst), consult on data extraction process, write the review, and perform previous work that was the foundation of the current study.

SL: appraise methodological quality of papers, write to authors of papers for additional information, obtain and screen data on unpublished studies, interpret data, and write the review.

GM: screen retrieved papers against inclusion criteria, appraise methodological quality of papers, interpret data, consult on meta-analytic techniques, write the review, and perform previous work that was the foundation of the current study.

At this time the group will retain the responsibility for updating the review.

Declarations of interest

MCA - none known

MNH - none known

MPJ - Mark P. Jensen is the author of two books on the topic of hypnotic analgesia ("Hypnosis for Chronic Pain Management: Therapist Guide" and "Hypnosis for Chronic Pain Management: Workbook"), and received royalties for sales of these books.

DRP - none known

SJL - none known

GHM - none known

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