Differential effects of hypnotic suggestion on multiple dimensions of pain

Medical hypnosis mitigates laboratory dyspnoea in healthy humans: a randomised, controlled experimental trial

QUESTION

Dyspnoea persisting despite treatments of underlying causes requires symptomatic approaches. Medical hypnosis could provide relief without the untoward effects of pharmacological approaches. We addressed this question through experimentally induced dyspnoea in healthy humans (inspiratory threshold loading (excessive inspiratory effort) and carbon dioxide stimulation (air hunger)).

MATERIAL AND METHODS

20 volunteers (10 women, aged 21-40 years) were studied on four separate days. The order of the visits was randomised in two steps: firstly, the "inspiratory threshold loading first" versus "carbon dioxide first" group (n=10 in each group); secondly, the "medical hypnosis first" versus "visual distraction first" subgroup (n=5 in each subgroup). Each visit comprised three 5-min periods (reference, intervention, washout) during which participants used visual analogue scales (VAS) to rate the sensory and affective dimensions of dyspnoea, and after which they completed the Multidimensional Dyspnea Profile.

RESULTS

Medical hypnosis reduced both dimensions of dyspnoea significantly more than visual distraction (inspiratory threshold loading: sensory reduction after 5 min 34% of full VAS versus 8% (p=0.0042), affective reduction 17.6% versus 2.4% (p=0.044); carbon dioxide: sensory reduction after 5 min 36.9% versus 3% (p=0.0015), affective reduction 29.1% versus 8.7% (p=0.0023)). The Multidimensional Dyspnea Profile showed more marked sensory effects during inspiratory threshold loading and more marked affective effects during carbon dioxide stimulation.

ANSWER TO THE QUESTION

Medical hypnosis was more effective than visual distraction at attenuating the sensory and affective dimensions of experimentally induced dyspnoea. This provides a strong rationale for clinical studies of hypnosis in persistent dyspnoea patients.

The sensory and affective components of pain: are they differentially modifiable dimensions or inseparable aspects of a unitary experience? A systematic review

BACKGROUND

Pain is recognised to have both a sensory dimension (intensity) and an affective dimension (unpleasantness). Pain feels like a single unpleasant bodily experience, but investigations of human pain have long considered these two dimensions of pain to be separable and differentially modifiable. The evidence underpinning this separability and differential modifiability is seldom presented. We aimed to fill this gap by evaluating the current evidence base for whether or not the sensory and affective dimensions of pain can be selectively modulated using cognitive manipulations.

METHODS

A rigorous systematic search, based on a priori search terms and consultation with field experts, yielded 4270 articles. A detailed screening process was based on the following recommendations: (i) evaluation of effectiveness; (ii) examination of methodological rigour, including each study having an a priori intention to cognitively modulate one of the two dimensions of pain; and (iii) sound theoretical reasoning. These were used to ensure that included studies definitively answered the research question.

RESULTS

After in-depth critique of all 12 articles that met the inclusion criteria, we found that there is no compelling evidence that the sensory and affective dimensions of pain can be selectively and intentionally modulated using cognitive manipulations in humans.

CONCLUSIONS

We offer potential explanations for this discrepancy between assumptions and evidence and contend that this finding highlights several important questions for the field, from both the research and clinical perspectives.

Underlying Mechanisms in Episodic Laryngeal Breathing Disorders

The study and management of episodic laryngeal breathing disorders (ELBD)—characterized by paradoxical laryngeal movement patterns and dyspnea—has traditionally focused on clinical presentation of these conditions. However, the underlying mechanisms driving these entities are largely unknown. This article provides a review of potential underlying mechanisms driving clinical expression in ELBD and suggests approaches to the future study of ELBD etiology.

Hypnotic relaxation results in elevated thresholds of sensory detection but not of pain detection

Background

Many studies show an effectiveness of hypnotic analgesia. It has been discussed whether the analgesic effect is mainly caused by the relaxation that is concomitant to hypnosis. This study was designed to evaluate the effects of hypnotic relaxation suggestion on different somatosensory detection and pain thresholds.

Methods

Quantitative sensory testing (QST) measurements were performed before and during hypnosis in twenty-three healthy subjects on the dorsum of the right hand. Paired t-test was used to compare threshold changes. The influence of hypnotic susceptibility was evaluated by calculating correlation coefficients for threshold changes and hypnotic susceptibility (Harvard group scale).

Results

During hypnosis significantly changed somatosensory thresholds (reduced function) were observed for the following sensory detection thresholds: Cold Detection Threshold (CDT), Warm Detection Threshold (WDT), Thermal Sensory Limen (TSL) and Mechanical Detection Threshold (MDT). The only unchanged sensory detection threshold was Vibration Detection Threshold (VDT). No significant changes were observed for the determined pain detection thresholds (Cold Pain Thresholds, Heat Pain Thresholds, Mechanical Pain Sensitivity, Dynamic Mechanical Allodynia, Wind-up Ratio and Pressure Pain Threshold). No correlation of hypnotic susceptibility and threshold changes were detected.

Conclusion

Hypnotic relaxation without a specific analgesic suggestion results in thermal and mechanical detection, but not pain threshold changes. We thus conclude that a relaxation suggestion has no genuine effect on sensory pain thresholds.

Trial Registration

ClinicalTrials.gov, Identifier: NCT02261155 (9^th October 2014).

Effect of hypnotic suggestion on fibromyalgic pain: Comparison between hypnosis and relaxation

The main aims of this experimental study are: (1) to compare the relative effects of analgesia suggestions and relaxation suggestions on clinical pain, and (2) to compare the relative effect of relaxation suggestions when they are presented as "hypnosis" and as "relaxation training". Forty-five patients with fibromyalgia were randomly assigned to one of the following experimental conditions: (a) hypnosis with relaxation suggestions; (b) hypnosis with analgesia suggestions; (c) relaxation. Before and after the experimental session, the pain intensity was measured using a visual analogue scale (VAS) and the sensory and affective dimensions were measured with the McGill Pain Questionnaire. The results showed: (1) that hypnosis followed by analgesia suggestions has a greater effect on the intensity of pain and on the sensory dimension of pain than hypnosis followed by relaxation suggestions; (2) that the effect of hypnosis followed by relaxation suggestions is not greater than relaxation. We discuss the implications of the study on our understanding of the importance of suggestions used in hypnosis and of the differences and similarities between hypnotic relaxation and relaxation training.

Children's ratings of the intensity and unpleasantness of post-operative pain using facial expression scales

This study explored whether global unidimensional self-report pain scales based on facial expression help children separately estimate the sensory and affective magnitude of post-operative pain. Ninety paediatric elective surgery patients (in two age groups: 5-9 and 10-15 years) used each of four scales to estimate pain intensity and pain affect during the first 2 days after surgery. The four scales were: Faces Pain Scale (FPS), Facial Affective Scale (FAS), and the Coloured Analogue Scale (CAS) (one for intensity and one for unpleasantness). As hypothesised, ratings on the FPS correlated more highly with analogue scale ratings for intensity than for unpleasantness, whereas ratings on the FAS correlated more highly with those on the analogue scale for unpleasantness than for intensity. Factor analysis indicated that although all measures loaded on a single dimension of distress, there was an additional weaker factor corresponding to a unique contribution of the FAS. No systematic age effects were observed. It was concluded that the FPS and the FAS may partly measure different aspects of the postoperative pain experience in children, although shared instrument variance may obscure true estimates of covariation in ratings of intensity and affective magnitude. The clinical relevance of the present results remains to be determined.

Pain reduction is related to hypnotizability but not to relaxation or to reduction in suffering: a preliminary investigation

The present study examined the facilitation of pain reduction through the use of a pain reduction protocol. The protocol emphasized converting pain sensations into visual and auditory representations, which then were manipulated through therapeutic suggestion. Hypnosis was not mentioned in the intervention, minimizing creation of expectancy effects related to hypnosis. At the conclusion of the study, the Stanford Clinical Hypnotic Scale was administered. Measures of relaxation and reduction of suffering were not related to hypnotizability. However, pain reduction was significantly related to hypnotizability (r = .55, P < .001). High hypnotizables had a greater reduction in pain than low hypnotizables, even though both had equivalent degrees of relaxation.

The effect of Rapid Induction Analgesia on subjective pain ratings and pain tolerance

The effect of Rapid Induction Analgesia (RIA) on pain tolerance and ratings of mechanically induced pain in the pain-sensitized forearm was investigated in 58 undergraduates. Posthypnotic suggestions of relaxation and analgesia did not influence pain ratings or tolerance, but relaxation ratings increased after RIA. When suggestions for analgesia were made throughout pain testing, ratings of pain unpleasantness at the pain tolerance point decreased more in the RIA group than in the attention control group. However, RIA did not influence pain threshold or tolerance. It was concluded that RIA was more effective in reducing subjective reports of pain (particularly the affective component) than in altering pain tolerance, and that maintenance of hypnotic suggestions was more effective than posthypnotic suggestions of comfort and relaxation in alleviating the affective component of pain.

Effects of an opioid antagonist on pain intensity and withdrawal reflexes during induction of hypnotic analgesia in high- and low-hypnotizable volunteers

The aim of this investigation was to study the effect of suggestions of hypnotic analgesia on spinal pain transmission and processing. Pain intensity and amplitude of nociceptive withdrawal reflexes to electrical stimuli were measured in 10 high- and 10 low-hypnotizable subjects during two sessions taking place at least 24 h apart under five conditions of: (1) pre-hypnosis; (2) neutral hypnotic relaxation; (3) suggestions of hypnotic analgesia; (4) suggestions of hypnotic analgesia after injections of either naloxone (1 ml, 1 mg/ml) or saline (1 ml) under double-blinded conditions; and (5) post-hypnosis. The conditions of naloxone or saline were allocated at random to either Day 1 or Day 2 in a double-blinded fashion. Results showed significant reductions of pain intensity during hypnotic analgesia, and a significant reduction in nociceptive reflexes during hypnotic analgesia on Day 1 in the highly hypnotizable group. No differences were found for low-hypnotizable subjects. The results support previous findings that pain intensity as well as the nociceptive reflex can be modulated by suggestions of hypnotic analgesia. While no effect of naloxone on pain intensity was found during hypnotic analgesia, naloxone significantly reversed the suppressive effect of suggestions of hypnotic analgesia on reflexes in high-hypnotizable subjects. Subsequent analysis showed that the effect of naloxone was associated with the intensity of the stimulus needed to elicit a reflex, and was unrelated to hypnotic susceptibility when controlling for stimulus intensity. These results suggest that the effect of naloxone was related to the greater stimulus intensities needed to elicit a reflex in the high-hypnotizable group, rather than to hypnosis or hypnotic susceptibility in itself. It is unclear why greater stimulus intensities were needed in high-hypnotizable subjects and further studies are needed. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.