Hypnosis and Pain: Time for a New Look

Laboratory Research in the Modern Era

For the most part, however, for 100 years after Elliotson (1843) and Esdaile (1846), interest in hypnosis and pain was largely academic, and confined to experimental work. Robert Sears (Sears, 1932) conducted a pioneering study of hypnotically induced pain analgesia, while Frank Pattie (Pattie, 1937) did the same for tactile anesthesia. They and others (e.g., Brown & Vogel, 1938; West, Niell, & Hardy, 1952) showed clearly that hypnotic suggestions altered conscious perception of the pain or touch stimuli, if not always of involuntary or indirect responses as well -- a topic to which I will return later. In the late 1950s and early 1960s, when experimental research on hypnosis was revived by Martin Orne, Ernest Hilgard, J.P. Sutcliffe, Theodore Barber, and their associates, hypnotic analgesia was there in the center of things (e.g., Barber, 1963; Barber & Hahn, 1962; Shor, 1962; Sutcliffe, 1961).

The attraction of analgesia to the first generations of modern hypnosis researchers was, I think, threefold. (1) With the possible exception of hypnotic amnesia (which after all gave hypnosis its very name), analgesia is the most dramatic of the alterations in consciousness observed in hypnosis. (2) It is also the most susceptible to "objective" measurement -- although, as I will indicate later, this feature has been somewhat overstated. (3) And, of all the phenomena of hypnosis, it has the most potential for practical use. Therefore, it is not surprising that when Jack Hilgard began his systematic study of hypnosis, he would quickly come to focus on analgesia.

The single most important fact about hypnosis is that there are individual differences in response to hypnotic suggestion. Unfortunately, hypnotizability cannot be predicted by the usual sorts of paper-and-pencil questionnaires, but must be assessed directly by means of performance-based assessments of  hypnotizability analogous to intelligence tests. The Stanford Hypnotic Susceptibility Scales, devised by Hilgard and Andre Weitzenhoffer in the late 1950s and early 1960s, begin with a standardized hypnotic induction procedure followed by a series of suggestions for imaginative experiences. The subject's response to each of these suggestions is scored according to an objective behavioral criterion. When these  scales are administered to unselected samples, they yield a roughly normal distribution of scores: while relatively few subjects are entirely refractory to hypnosis, what Hilgard referred to as "hypnotic virtuosos" comprise only about 10%-15% of the population. 

The relevance of hypnotizability to hypnotic analgesia is shown clearly in an early laboratory study by Hilgard involving cold-pressor pain stimulation in which subjects' hands and forearms are immersed in circulating ice water (Hilgard, 1967; Hilgard, 1969, 1978). The result is a very good laboratory analog of clinical pain.  Under normal conditions, pain mounts rapidly over the course of a minute or so, as indicated by subjects' reports on an open-ended scale. However, when hypnotized and given suggestions for analgesia, subjects of relatively high hypnotizability gain substantial pain relief: they may still feel some pain, but even after 60 seconds the majority find the levels to be tolerable.

Of course, pain has two components, measured on the McGill Pain Questionnaire as sensory pain, providing information about the location and severity of an injury, and suffering, or the "meaning" of the sensory pain.  During his psychophysical investigations Hilgard found that hypnosis alters both of these components. In one study, involving ischemic muscle pain produced by cutting off the flow of blood to the forearm, both pain and suffering were reduced essentially to zero in a group of highly hypnotizable subjects (Knox, Morgan, & Hilgard, 1974).

 A recent brain-imaging study by Rainville and his associates showed that strategically worded suggestions can dissociate the two components of pain, selectively altering one but not the other (Rainville, Duncan, Price, Carrier, & Bushnell, 1997).  These investigators then used this dissociation in a provocative brain-imaging study which indicated that the two components of pain have different biological substrates: sensory pain in the primary somatosensory cortex, and suffering in the anterior cingulate cortex -- the same place where other investigators have recently located romantic love!  (The figure shows activation in the right hemisphere because the pain stimulus was applied to the left hand.)

Along the same lines, an unbelievably spartan study by John Stern and his associates compared the effectiveness of seven different challenging agents -- hypnosis,  acupuncture, placebo acupuncture, morphine, aspirin, diazepam, and placebo pill -- against two kinds of pain in a within-subjects design that entailed a total of 280 pain trials per subject (Stern, Brown, Ulett, & Sletten, 1977). Analysis of the subjects' cold-pressor pain ratings showed that hypnosis was superior to all other challenging agents, especially for those subjects who were highly hypnotizable. Interestingly, only hypnotic analgesia was correlated with hypnotizability. Similar findings were obtained for ischemic muscle pain.

More recently, a meta-analysis of clinical and experimental studies reported by Montgomery and his colleagues compared hypnosis against a number of other cognitive-behavioral interventions (Montgomery, DuHamel, & Redd, 2000).  The studies in question were a mix of the clinical and experimental, with most of the experimental studies involving cold-pressor pain and the clinical studies including patients suffering from both burns and cancer. Comparing hypnosis to a no-treatment control, Montgomery et al. found that the effect of hypnosis corresponded to a standardized effect size of d = .74, which counts as a moderately large effect size by conventional standards. More than a quarter of the comparisons yielded very large ds of 1.0 or more. 

The effect was bigger in clinical patients than in experimental subjects,  and especially large among those of high hypnotizability. Comparing hypnosis to a variety of other cognitive-behavioral treatments tested in the same studies, Montgomery et al. found no particular advantage for hypnosis, but this analysis did not take hypnotizability into account.  It is likely that hypnotizable subjects would have gained more from hypnosis than from any other psychological treatment.

Clinical Studies in the Modern Era

Even before systematic laboratory studies appeared to support the practice, clinicians in the field were returning to hypnosis. In part, the revival of interest in clinical hypnosis was stimulated by the successful use of the technique during World War II, where chemical analgesics and anesthetics were not always available for the treatment of wounded soldiers. In preparing their authoritative review of Hypnosis in the Relief of Pain, Hilgard and Hilgard uncovered more than two dozen cases, published between 1955 and 1974, in which hypnosis served as the sole analgesic or anesthetic agent (Hilgard & Hilgard, 1975). One enthusiastic practitioner of clinical hypnosis even had a film made of her own cosmetic dermabrasion, essentially sandpapering off whole layers of facial skin with hypnosis as the sole analgesic, just to show it could be done. Recently, a group of Belgian investigators reported a series of 1,650 surgical cases attempted with "hypnosedation", in which fewer than 1% required a switch to general anesthesia (Faymonville, Meurisse, & Fissette, 1999).  Nevertheless, the general consensus is that vanishingly few patients, far fewer than the 10% or so who qualify as hypnotic virtuosos, are hypnotizable enough to tolerate such procedures with hypnosis alone. This should only be attempted as a last resort, and the real applications of hypnosis lie elsewhere.

One of these applications is obstetrics. So far as labor pain is concerned, regional and general anesthetics will do the job, but ever since Queen Victoria took chloroform during the delivery of her eighth child, there has been concern that drugs might increase the risk to the fetus, detract from the experience of childbirth, or interfere with the mother-child bond. These concerns help explain why chemical anesthesia, quickly embraced for other surgical procedures, was not widely adopted for obstetrics until late in the 19^th century (Pernick, 1985). By the 1950s, obstetricians were already familiar with other psychological techniques for pain reduction, such as Dick-Read's "natural childbirth", the "Lamaze method", and Schultz's autogenic training. It seems likely that the desire to avoid drugs whenever possible explains why some of them looked to hypnosis as a scientifically respectable, more mainstream alternative.

In any event, a pioneering large-scale study by Ralph August reported on 1000 consecutive cases, in which hypnosis was attempted in 850 (August, 1961). Of these, 58% required no medication at all, 38% required only minor analgesics such as Demerol, and 4% abandoned hypnosis entirely in favor of local or general anesthetics. At about the same time,  Davidson reported that the benefits of hypnosis were equal to those of natural childbirth in the first stage of labor, and superior in the second stage (Davidson, 1962). Other early reports indicated that hypnosis is associated with decreased frequency of premature labor (and thus spontaneous abortion), reduced duration of labor, more rapid recovery from birth asphyxia in the neonate, and increased satisfaction with the childbirth experience on the part of the mothers.

Similar results were obtained in cancer treatment. Some enthusiasts have tried to treat cancer directly with hypnosis, suggesting that subjects imagine "good cells" fighting off "bad cells" and the like. This rarely works, of course, and when it does seem to work the remission is almost certainly adventitious and has nothing to do with hypnosis. Nevertheless, the patients often obtain considerable relief from pain caused either by cancer or its treatment.  Cangello studied 81 patients, 73 of whom seemed to be at least moderately hypnotizable (Cangello, 1961). Of this subgroup, his clinical impression was that almost 70% achieved good to excellent relief of chronic pain. For the 22 patients for whom narcotics had been prescribed for pain control, 63% showed an immediate decrease in medication usage to 50% or less of base levels; this reduction lasted for a week in 54%, and for 1 to 3 months in 18%, with no reinforcement of the hypnosis.

Unfortunately, these studies appeared on the eve of a revolution in medical practice. Clinical medicine has always been based on biology, of course, but the golden age of antibiotics, in the 1940s and 1950s, culminated in the apparent conquest of infectious disease and prompted advances in immunology that promised to prevent disease at its source. New generations of analgesics and anesthetics came onto the market, as well as new procedures such as epidural anesthesia for childbirth and conscious sedation for outpatient procedures. These developments led physicians once again to turn away from hypnosis and toward drugs.

A study of hypnosis in dentistry makes the point (Gottfredson, 1973).  Gottfredson found that 56% of hypnotizable patients were able to complete their procedure without any chemical analgesic at all, and this figure was 75% for those of relatively high hypnotizability. However, local anesthetic produced a comparable effect, without any individual differences in response. Although mesmeric coma was used for dentistry prior to the introduction of chemical anesthesia, and many dentists still use hypnosis to treat anxiety in the chair, chemical analgesics and anesthetics are simply more reliable, and these days hypnosis is rarely used for the relief of dental pain.

In the late 1970s, Joseph Barber (Barber, 1977) claimed a 99% success rate with an innovative technique, which he calls "rapid induction analgesia", in a series of unselected patients. A follow-up study by Gillett and Coe (Gillett & Coe, 1984) yielded a success rate more like Gottfredson's, 52%. Outcome was uncorrelated with hypnotizability, however, suggesting that whatever effects RIA has are not mediated by hypnosis.

Despite these promising results, there have been virtually no controlled, quantitative studies of hypnotic analgesia in clinical settings (Chaves, 1989; Chaves & Dworkin, 1997; D'Eon, 1989; Holroyd, 1996; Milling & Costantino, 2000; Pinnell & Covino, 2000). One exception is in the area of obstetrics, where more recent studies have confirmed and extended the early results of August and Davidson (Brann & Guzvica, 1987; Freeman, MacCauley, Eve, & Chamberlain, 1986; Jenkins & Pritchard, 1993). Another is cancer, where a number of studies support the use of hypnosis.  In a pioneering study, Josephine Hilgard and Sam LeBaron (Hilgard & LeBaron, 1982) offered hypnosis to 63 consecutive children who were receiving bone marrow aspirations required for treatment of leukemia. Of the 24 who accepted the referral, 19 proved to be at least moderately hypnotizable. After only one session of training, 10 of these patients were able to reduce felt pain during the procedure by at least three points on a 10-point scale; with a single additional training session, the success rate rose to 15 of 19 when the procedure was repeated about six weeks later. None of the five less hypnotizable subjects reported substantial relief of pain on either occasion. Similar findings were obtained in another study of children with leukemia being treated with bone marrow transplants (Syrjala, Cummings, & Donaldson, 1992).

Mechanisms of Hypnotic Analgesia

Although many early clinical studies were relatively primitive by the standards of modern research, they clearly demonstrated that hypnosis is an effective challenging agent for both clinical and experimental pain. The next question is how hypnosis works, and for that we must return to the laboratory. One theorist, taking a skeptical view of things, suggested that the reason hypnosis works is that most surgical procedures don't really hurt anyway, and to the extent they do, hypnotized subjects try to please their physicians by reporting otherwise. I think that Esdaile had the most effective response to this claim when he wrote of the large numbers of patients flocking to his clinic for the removal of tumors:

There must be some reason for this, and I only see two ways of accounting for it: my patients, on returning home, either say to their friends similarly afflicted, "Wah! brother, what a soft man the doctor Sahib is! he cut me to pieces for twenty minutes, and I made him believe that I did not feel it. Isn't it a capital joke? Do go and play him the same trick...". Or they say to their brother sufferers, -- "look at me; I have got rid of my burthen..., am restored to the use of my body, and can again work for my bread: this, I assure you, the doctor Sahib did when I was asleep, and I knew nothing about it...".

One thing we know is that hypnosis is not mediated by stimulating the flow of endogenous opiates. In a collaboration with Jack Hilgard, Avram Goldstein, who originally discovered the existence of specific opiate receptors in the brain, showed that naloxone, an opiate antagonist, has no effect on hypnotic analgesia (Goldstein & Hilgard, 1975). This finding has been subsequently been confirmed by other investigators (Barber & Mayer, 1977; Spiegel & Albert, 1983).  For example, Moret and his colleagues gave unselected subjects suggestions for hypnotic analgesia during cold-pressor pain. The suggestions were successful in relieving pain by about 50% on average, but this success was not accompanied by increases in serum beta-endorphin levels. Nor did the infusion of Naloxone have any effect on the effectiveness of hypnotic analgesia. I don't wish to sound like a dualist, but it appears that hypnotic analgesia is mediated by psychological processes, not by any indirect physiological effects.

Although some theorists have linked hypnosis to expectancy processes, it also appears that hypnotic analgesia is more than a placebo.  In one study, McGlashan, Evans, and Orne recruited subjects for a study comparing hypnosis to medication in the relief of ischemic muscle pain (McGlashan, Evans, & Orne, 1969). Unbeknownst to the medical student who was running the study, during the drug trials the subjects received placebo packed in Darvon capsules. Insusceptible subjects got equivalent pain relief from hypnotic suggestion and from placebo. However, the hypnotizable subjects obtained substantially more relief from hypnosis than they did from placebo. The study suggests that hypnosis, like all effective analgesics, has a placebo component mediated by expectancies of success. Placebos are important, and they're ubiquitous, but, in hypnotizable subjects at least, hypnosis is more than placebo.

As an alternative to the endorphin and placebo theories, Jack Hilgard has proposed that hypnotic analgesia involves a division of consciousness, in which an amnesia-like barrier prevents conscious awareness of pain (Hilgard, 1973; Hilgard, 1977). This proposal helps make sense of one of the paradoxes of hypnosis, which is that it alters people's self-reports of pain but not their physiological responses to the pain stimulus. One interpretation of this difference is that the subjects are really feeling the pain after all, but we also know on independent grounds that physiological measures are relatively unsatisfactory indices of the subjective experience of pain. From the perspective of Hilgard's neodissociation theory of divided consciousness, the reduced self-ratings are accurate reflections of the subjects' conscious experience of pain, while the physiological measures show that the pain stimulus has been registered and processed outside of conscious awareness by the sensory-perceptual system. Put another way, hypnotic analgesia impairs the explicit perception of pain while leaving the implicit perception of pain intact (Kihlstrom, 1987; Kihlstrom, 1996; Kihlstrom, Barnhardt, & Tataryn, 1992). This dissociation is of considerable interest to those of us who are interested in consciousness and unconscious mental life. But because it is the conscious awareness of pain that bothers both experimental subjects and medical patients, the fact that hypnosis does not affect some physiological responses should not stand in the way of its clinical use.

On the other hand, the late Nicholas Spanos (Spanos, 1986) argued that hypnotic analgesia is achieved by the deployment of certain coping strategies identified by Donald Meichenbaum and others as stress inoculation (Meichenbaum, 1975; Meichenbaum & Turk, 1982). Now, there's no doubt that distraction, relaxation, imagining situations inconsistent with pain, and resistance to "catastrophizing" can result in substantial pain relief -- the question is whether these strategies account for hypnotic analgesia. Apparently, they do not (Hargadon, Bowers, & Woody, 1995; Miller & Bowers, 1986, 1993).

In one test of the stress-inoculation theory, Miller and Bowers ran groups of hypnotizable and insusceptible subjects through an experiment involving cold-pressor pain. One third of the subjects in each group was hypnotized, and given suggestions for analgesia. Another third was hypnotized, but not given any analgesia suggestions. The remaining subjects were not hypnotized at all, but were instructed in the use of stress inoculation strategies of the sort that Spanos had proposed as mediators of hypnotic analgesia. The result was a highly significant, and revealing, interaction between treatment condition and hypnotizability: stress inoculation worked as expected, producing substantial pain relief, but hypnotizable and insusceptible subjects achieved the same effect. By contrast, hypnotic suggestions for analgesia were much more effective for hypnotizable than for insusceptible subjects. Note, too, that for hypnotizable subjects, hypnotic analgesia produced more pain relief than stress inoculation. But the important observation is that hypnotic analgesia is mediated by hypnotizability, while stress inoculation is not.
 

In a later study, Miller and Bowers assigned subjects of low and high hypnotizability to stress inoculation and hypnotic analgesia conditions, but with a somewhat fiendish twist: during the cold-pressor tests the subjects were also administered a difficult vocabulary test. The idea was that consciously deployed cognitive strategies, such as those taught in stress inoculation, ought to consume attentional capacity and impair performance on the vocabulary test. This was, in fact, the outcome for the subjects in the stress inoculation condition. In the hypnotic condition, however, vocabulary scores were essentially unaffected, and for hypnotizable subjects actually went up a little.

In the third and final paper in the series, Hargadon, Bowers, and Woody gave hypnotizable subjects analgesia suggestions of two types -- one suggested a lot of counterpain imagery, the other did not. Of course, some subjects in the imagery condition didn't use imagery, and some in the no-imagery condition used imagery anyway, and some just focused on the pain and catastrophized. The important result was that the use of imagery, whether instructed or spontaneous, had no impact on the success of hypnotic analgesia in these hypnotizable subjects -- suggesting, once more, that counterpain imagery is not central to hypnotic analgesia.

This set of results strongly suggests that whatever its underlying mechanisms, hypnotic analgesia is not mediated by stress inoculation and other consciously deployed cognitive strategies. For insusceptible subjects, incapable of responding to hypnotic suggestions, stress inoculation strategies can produce considerable benefit; but for hypnotizable subjects, hypnotic analgesia is probably preferable to stress inoculation as a psychological technique to control pain. In my view, this leaves Hilgard's neodissociation theory as the most viable explanation of hypnotic analgesia. We may hope that our growing understanding of unconscious mental life will shed more light on the mechanisms by which this dissociation takes place (Kihlstrom, 1992a; Kihlstrom, 1997).

 Empirical Support for Efficacy

Let us set theoretical considerations aside and return to the practical utility of hypnotic analgesia in clinical situations. Perhaps the best evidence in this regard comes from two randomized studies reported by Lang and her colleagues with patients undergoing a variety of invasive diagnostic and treatment procedures (Lang et al., 2000; Lang, Joyce, Spiegel, Hamilton, & Lee, 1996).  In the more recent of these, reported in the Lancet earlier this year, all patients received standard patient-controlled conscious sedation for the procedure, with one third receiving hypnosis and another a structured attention manipulation. The addition of hypnosis afforded significantly greater pain relief than did conscious sedation alone, with the attentional manipulation falling somewhere between.  In addition, patient anxiety levels were also lower with hypnosis. 

Both groups receiving the adjunctive psychological treatment requested, and received, less medication than did those in the standard group. Finally, there were fewer adverse events, such as oxygen desaturation, hemodynamic instability, bleeding from the puncture site, oversedation, and vomiting to distract the surgical team. 

Perhaps for these reasons, the surgical procedures took significantly less time for the hypnosis group than for the standard care group, by about 15 minutes on average.  Unfortunately, Lang and her colleagues did not assess hypnotizability in their patients, but it is a pretty certain bet that these benefits were much greater for those who were at least moderately hypnotizable.

Twice in its history, hypnosis has sought a place in the clinician's repertoire of methods for pain control. The first time was in the middle of the 19^th century, before hypnosis even had its name. Unfortunately, it was quickly overshadowed by the discovery of chemical anesthetics. The second time was in the middle of the 20^th century, in parallel with the emergence of a substantial body of laboratory research on hypnosis and its underlying mechanisms. This time, although the scientific status of hypnosis was widely acknowledged, the practical use of hypnosis fell victim to the renewed biologization of medical practice. Even so, there is no question that hypnotic analgesia deserves the status of an empirically supportive psycholoical treatment for pain (Chambless & Hollon, 1998; Lynn, Kirsch, Barabasz, Cardena, & Patterson, 2000; NIH Technology Assessment Panel, 1996). To be blunt, hypnotic analgesia is efficacious and specific: its efficacy is supported by a large number of methodologically sophisticated studies conducted by many independent investigators; it is not merely a placebo; in those who are hypnotizable, it is superior to both placebo and alternative psychological treatments such as stress inoculation.  Based on the available evidence, approximately 50% of unselected patients can obtain significant pain relief from hypnosis.

The current environment of healthcare, in which consumers are seeking effective alternatives to the chemical interventions that are the standard of care, provides hypnosis with an opportunity to rise again. It is complementary medicine that works, and which rests on an impressive base of laboratory research. But this same environment also offers hypnosis a new challenge: that it be not simply effective, but cost-effective as well. These days, when I tell practitioners about hypnosis, they believe the evidence, but they ask whether it is reimbursable by managed care. Fortunately, many health plans now pay for complementary treatments, so long as there is evidence of their effectiveness. But this practice is likely to continue only so long as the treatments in question are cost-effective as well. The available evidence strongly indicates that adjunctive hypnosis can improve the quality of care, by reducing patient anxiety and the number of adverse events; and that it is cost-effective, by reducing the length of procedures and the use of expensive medications. Now that healthcare consumers have become interested in "natural" alternatives to traditional medicine, and demanding that their health plans pay for them, the time is ripe for a new look at hypnosis and pain, with quality of care and cost-effectiveness in mind.

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