Martin T. Orne, M.D., Ph.D University of Pennsylvania
Modern dentistry, like modern surgery, could not have evolved without effective techniques to control pain. In contrast to surgery, however, dental procedures are rarely carried out under general anesthesia, and consequently pain and the fear of pain continue to play a Conspicuous role in dental practice. One of the important stressors which complicate the dentist's life is the fear response elicited in many patients by even the most innocuous dental procedures. Every practitioner has had at some time or another to come to terms with the problem of having to inflict some unavoidable pain on his patient in the context of doing essential dental procedures. The stoic patient is seen by many dentists as a boon, whereas the patient who is anxious and fearful and who flinches at every procedure evokes emotions ranging from anxiety and guilt to irritation and anger. While the trained professional has learned to control his feelings in the patient's presence, few dentists can remain unaffected by such a patient. In many communities there are some who have made it a specialty to care for the difficult dental patient, but while this may solve the problem in extreme cases, no practitioner can avoid dealing with the difficulties created by his patient's feeling of pain and the emotional response it evokes, not only in his patient but also in himself. Today I hope to deal with some aspects of the cognitive control of pain that seem to be relevant to the dental situation. While I have nut personally experienced the discomfort associated with having to inflict pain in order . to provide dental care, and the conflict between needing to continue
214 THE MECHANISM AND CONTROL OF PAIN
in order to do the job right and wanting to stop in order to put an end to the patient's suffering, I have, alas, had ample experience at the patient's end of this dyadic interaction which has helped to develop my interest in these issues!
THE NATURE OF PAIN
Much is known about the kinds of stimuli which produce pain, the kind of fibers which transmit it, the pathways by which the nervous impulse reaches the cortex, some of the mechanisms which modulate the experience of pain, and the manner in which one may strive to block the pain sensation cortically and peripherally. It is unlikely that any of you here fail to know more about these aspects of pain than I. It is, of course, essential for a dentist, as for an anesthesiologist, to know how to safely and effectively block the transmission of pain impulses from the periphery to the cortex. However, it is this very skill of controlling pain by physical means, which is acquired over many years, that leads one to think of the appreciation of pain as though it were strictly a response to an objective stimulus, analogous to other forms of perception. However, while it is essential to comprehend the intricacies of peripheral pain pathways in detail, it is equally necessary, once these are learned and understood, to step back and view pain from a broader perspective as well.
THE SUPPRESSION OF PAIN WITH HYPNOSIS
To those of us who perceive pain as a purely physical entity, few phenomena are as troubling as hypnotic anesthesia. The induction of hypnosis is a remarkably simple procedure. The patient is instructed to focus his attention, perhaps to think about being relaxed and his eyes being heavy and closing, and to allow himself to drift off as in a daydream, or perhaps to feel as if he is going to sleep. Typically the procedure takes only a few moments. No drug is given and nothing dramatic is done to the patient. Nonetheless, a patient who only moments earlier had shown intense fear and evidence of pain may respond to suggestions that his body is becoming insensitive to pain, and as these suggestions are continued, he not only allows himself to be examined with no evidence of discomfort, but a broad range of normally painful procedures, including extractlons, may be carried out with no sign of discomfort.
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This course of events is startling, not because surgery is carried out on a relaxed and comfortable patient (a great many anesthetics allow this to occur), nor even because the patient is awake and comfortable (either local or regional anesthetics of course permit surgery under these conditions), but rather because there is no obvious mechanism to explain the suppression of pain. The puzzle is further complicated by the absence of clear-cut physiological changes associated with entering hypnosis. For example, suggestions of drowsiness may cause the patient to look as though he is asleep, yet he continues to respond to the hypnotist's voice, shows no unique changes in the EEG, and is able to perform complex cognitive tasks without difficulty. Given appropriate suggestions, the patient may show every evidence of being wide awake, but nonetheless he will assert that he feels no discomfort even as major surgery is being carried out. The idea that a psychological process, occurring relatively quickly and easily in normal individuals and unaccompanied by unique physiological changes, can cause profound alterations in an individual's response to obviously painful stimuli seems to fly against common sense expectations. It is hardly surprising that some observers are loath to accept the patient's assertion that he feels no pain under these circumstances.
Although the patient is for the most part relaxed during surgery, careful observation reveals that as the surgeon pulls on the peritoneum or manipulates some other organ richly endowed with pain receptors, changes in both heart rate and respiratory patterns can be seen to occur, at times associated with facial grimaces that might suggest pain. Not only is it possible to observe such changes in the naturalistic setting of the operating room, but in carefully controlled laboratory studies the subject who is in deep hypnosis and reports total insensibility to pain nevertheless shows the kinds of changes in heart rate and galvanic skin response (GSR) usually associated with pain stimuli.' Similarly, when dental procedures are carried out., it is not uncommon for patients to grimace and to give other transient behavioral evidence of pain while nonetheless asserting, when asked, that they feel no discomfort.
These inconsistencies in the response to pain experienced while under hypnosis have long confused investigators and have raised serious questions in the minds of some observers about the "reality" of hypnotically induced anesthesia. One way in which the phenomenon has been explained is to contend that the hypnotized patient is so eager to please the hypnotist or is so anxious to maintain the role of being a hypnotized subject or has some other personal-or even ulteriormotive that he is willing to bear the pain and make believe that he is comfortable. Much in the same way as the Greek stoics or the American
216, THE MECHANISM AND CONTROL OF PAIN
Indians placed great emphasis on a brave man's ability to bear pain without outward signs of suffering, so, the argument goes, does the hypnotized subject strive to control both the external appearance of pain and his verbal reports. Only his physiological responses and his occasional inability to suppress a facial grimace reveal his suffering.
The physiological data clearly indicate that pain perception must take place at least at the level of the thalamus, whereas there is other evidence, to be discussed later, to show that pain perception also occurs at the cortical level.
Several investigators'-' have observed that when painful stimuli are applied to a hypnotically anesthetized limb a deeply hypnotized subject will assert verbally that he feels no pain, but at the same time he may indicate by means of automatic writing his appreciation of pain at another level. Automatic writing is a phenomenon-relatively easily induced by giving a deeply hypnotized subject a pencil and the suggestion that the pencil will begin to write without his awareness of what is being written or, for that matter, that writing is occurring at all. Most interestingly, if the subject is asked to examine the material he has produced he will often disown it and insist that the ideas and the sen-iments expressed are not his own.
Recently Hilgard' has extended his systematic studies of hypnoanalgesia using a technique of automatic speaking. In addition to the usual kinds of verbal pain reports which are obtained while the subject is exposed to ischemic muscle pain, Hilgard instructs his deeply hypnotized subject that when he places his hand on the subject's right shoulder, that part of him which is not normally responsive but is aware of all aspects of his experience will provide its own verbal pain report. While the hypnotized subject is asserting that he feels no pain, Hilgard obtains pain ratings from what lie terms the "hidden observer," which clearly indicates a considerable degree of pain at another level of awareness. Interestingly, however, these reports are given without the effect of suffering which would otherwise accompany them. Thus, although the deeply hypnotized subject reports experiencing no pain, the "hidden observer" typically reports awareness of some pain, but characteristically less than one obtains from the same subject exposed to the same stimulus in the waking state.
These data indicate That the pain is perceived at a cortical level and that the individual is not merely suppressing his suffering. Thus, patients who have had surgery under hypnoanesthesia continue to assert the effectiveness of the suggested pain relief long after surgery; even when pressed by skeptical friends, they continue to insist postoperatively that they did not in fact endure any suffering. These pa-
217 Cognitive Factors in the Control of Pain
tients also require little if any postoperative analgesia, a behavior that is often markedly different from that which the same patients exhibited under prior surgery. When hypnoanalgesia is used in other contexts such as the treatment of intractable pain, as in terminal cancer, the need for narcotics is rapidly reduced and usually eliminated. In each of these instances one might still argue that the patient is somehow trying to please the hypnotist, but in many instances this rather implausible argument simply cannot be maintained. For example, one woman who had delivered a child under hypnoanesthesia moved to another city and went to great trouble to seek another obstetrician who used this technique. If she had really suffered discomfort and merely inhibited its expression during the first delivery, it is difficult to understand why she would choose to go through such a charade yet another time.
Analogous evidence from the laboratory context can be cited. Typically, subjects participating in pain experiments will assert not only to the investigator himself but also to their friends away from the laboratory that they experienced no discomfort in the hypnoanalgesic condition. Not infrequently a subject who has taken part in such a study, when asked if he would be willing to participate in a similar experiment in the future, indicates that he is quite prepared to repeat the hypnoanalgesia segment but under no circumstances would he repeat the waking control part of the study, during which he had to experience the same pain stimuli without hypnosis. Although it is difficult to prove that subjects are not willfully lying when they describe their experience during hypnoanalgesia, such an explanation is extremely implausible, and no proponents of such a view, have been able to persuade volunteers to undergo major surgery without any form of anesthesia. From the point of view of the dentist, it is of particular interest that the very patients who appear most phobic in the dental situation are often those who can respond most profoundly to hypnotic suggestions and who are able to obtain virtually total relief from all pain, more successfully so than even the most stoic unhypnotized individual.
The lack of objective measures of pain needs to be recognized as a serious problem in all pain research, and indeed studies of hypnotically induced analgesia have been particularly sensitive to the problems of the validity of subjective reports-issues that need to be addressed in evaluating any reported analgesic effects. Certainly, care must be taken to obtain subjects' reports in a context that is most likely to maximize honest reporting. Moreover, although it would be desirable to have an index of pain other than subjective reports, it should be kept in mind that these reports are the only meaningful way of indexing pain, which is after all a subjective experience-whether or not it is associated with
218 THE MECHANISM AND CONTROL OF PAIN
concomitant physiological alterations. From our point of view, neither a physiological response nor a behavioral response can ever be more than an imperfect correlate of pain. The phenomenon itself resides in the patient's subjective experience of suffering, which may be more or less adequately reflected in a particular measure employed in a particular study.
In summing up the phenomenon of hypnotically induced analgesia, it seems clear that some deeply hypnotized subjects are able to tolerate surgical pain and analogous painful stimuli in the laboratory while asserting that they feel no discomfort. With appropriate techniques these subjects report an awareness of pain at another level without, however, evidence of suffering. The patient who asserts that he feels no pain seems to be truthful, in describing what he is actually experiencing, even though at some cortical level the pain is perceived. However, the mechanisms by which hypnoanalgesic effects can be explained remain to be elucidated.
NATURE OF HYPNOTICALLY INDUCED ANALGESIA
It is well known that psychological factors affect pain perception. Consider, for example, the athlete who sustains a fracture but continues to play until the game is completed without even becoming aware of an injury that normally would cause exquisite pain; or the dental patient who suffers intensely and on reaching the dental chair is no longer aware of his pain; or the patient who obtains profound relief from an injection of a saline placebo; and so on. There is a tendency to group all psychological mechanisms together, assuming somehow that they arc similar or even identical. Particularly the placebo effect is generally conceived of as a form of suggestion closely related to hypnosis.
Because it is not possible to review here the voluminous literature on hypnotic analgesia, we will limit ourselves to research in our laboratory which addresses the particular relationship between hypnotic analgesia and the placebo effect. First, we sought to compare the effect of hypnotically induced analgesia with the effect of placebo. Second, we wished to study the effect of suggestions of analgesia on highly hypnotizable subjects as opposed to unhypnotizable subjects. An elaborate experimental design was developed to control for experimenter bias and similar problems in research by employing two groups of subjects, one that was highly hypnotizable and the other unable to respond to hypnosis. A hypnotic induction procedure was employed in
219 Cognitive Factors in the Control of Pain
which there is no test of response to hypnotic suggestion that would result in a different response in these two groups of subjects. The two groups were treated in the identical manner by an investigator who was unaware of the subjects' past experience with hypnosis. These conditions make the procedure closely analogous to the double-blind technique used in psychopharmacology.
This approach takes advantage of the fact that the ability to enter hypnosis is a remarkably stable attribute of the individual. After three sessions the correlation between two succeeding standardized measures of hypnotizability is in excess of 0.9. It is therefore feasible to test subjects several times, selecting the two groups to be compared from the two ends of the distribution: those who are consistently highly responsive and those who are consistently unresponsive over repeated sessions. Since one group is essentially unresponsive to hypnotic suggestions, any effects observed in that group cannot be ascribed to hypnosis. At the same time, both groups will try to follow instructions to the best of their ability and be responsive to verbal and nonverbal cues indicating how they should behave. The one problem with this control group is that unhypnotizable subjects will have failed to respond in several experiences, and although it is possible to keep the hypnotist blind as to their status, they themselves will be aware that they are in essence unresponsive. Consequently, these subjects may well perceive the demands of the experimental situation quite differently from hypnotizable subjects. To solve this subtle but crucial problem in the design, we modified the procedure by including a special session designed to convince the unhypnotizable group that they could actually respond to hypnotic suggestions sufficiently well for the purposes of the study.
Another hypnotic session was arranged for the unhypnotizable subjects with a different hypnotist who employed a technique based exclusively on relaxation. Great care was taken not to test the ability of these subjects to respond to hypnotic suggestions and thereby to avoid providing feedback that would indicate to them their continuing inability to respond. The subjects were treated as though they were responding extremely well to the particular procedure being employed. Even unhypnotizable individuals reach a state of profound relaxation under these circumstances. Once this had occurred, the hypnotist began to suggest analgesia of the right hand, again taking great care to induce the suggestion slowly and deliberately.
The analgesia suggestion was tested with electric: shocks from an inductorium, and each subject was asked to compare the intensity of the shock in the analgesic hand with that in the normal hand. Although
220 THE MECHANISM AND CONTROL OF PAIN
these subjects had been unhypnotizable, all of them experienced a considerable degree of analgesia because (unknown to them) the setting of the transformer was altered appropriately-they actually received less shock to the hand where analgesia had been suggested than to the normal hand. This manipulation was done carefully and within plausible limits. As a consequence, these subjects expressed considerable fascination and pleasure with the success of the analgesia suggestion. Careful postexperimental discussion supported the behavioral observations that these individuals were indeed persuaded about their ability to respond to analgesia suggestions. One subject who still doubted his responsiveness was excluded from participation.
This unusual manipulation resulted in a group of subjects who were essentially unresponsive to hypnosis as established by careful evaluation long before the experiment (and whose lack of responsivity persisted after the study), but who nonetheless believed themselves to be capable of responding to a particular form of hypnotic induction and to the suggestion of analgesia.
Subjects were then solicited for an experiment involving pain tolerance, and during a baseline session their tolerance for ischemic pain was established. The experimental population consisted of 12 highly hypnotizable and 12 unresponsive subjects who were convinced of their ability to experience hypnotic analgesia successfully. They were required to perform work that was quantified by the length of time pain was tolerated as well as by the amount of water they were able to pump while blood flow was occluded by means of a blood pressure cuff inflated to 200 nun Hg. Subjects were urged to pump as long as they could, and the initial pain threshold (when the sensation in the arm was first noticeably painful) and pain tolerance (when pain was so unbearable that they were unable to continue) were noted.
After the initial baseline session, all subjects returned and were tested by an experimenter who was not familiar with their previous hypnotic experiences in a session where a relaxation method of hypnotic induction was employed and analgesia was induced in one arm. The same technique was employed of assessing pain threshold and tolerance that was used during the first session for testing hypnotically induced analgesia.
All subjects were asked to return for yet a third session. It was explained to them that during this session a drug would be used to help establish how effective hypnotic; analgesia really was. It was pointed out that a powerful new analgesic drug was being employed that was known to suppress ischemic muscle pain. It was implied that the drug would work well and that this would allow us to see how closely
221 Cognitive Factors in he Control of Pain
hypnotic analgesia could approximate the drug effect. The experimenter himself believed he was administering dextropropoxyphene (Darvon) and placebo in a double-blind manner. The pharmacy, however, had delivered two bottles, both of which were in fact placebo: one had been labeled Darvon and one placebo. The secretary then made up the usual envelopes from these bottles. Since no one in the laboratory other than myself was aware that there was no active drug, we created a firm belief in the experimenter that he was carrying out a drug study. I However, all subjects received placebo, making the entire sample available for analysis.
Figure 1 summarizes our findings of the effect on pain threshold: the more sensitive, albeit less reliable, measure of analgesic, response
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clearly shows that both groups responded to the hypnotic induction procedure. Although the pain threshold of the highly hypnotizable group is raised considerably more than that of the insusceptible group, the increment in pain threshold of the insusceptible group is nonetheless significant. In contrast, the change in pain threshold to placebo is identical in the groups. The pain tolerance findings show little change in the nonhypnotizable as opposed to a dramatic change in the hypnotizable group in response to posthypnotic suggestion.
The relationship between the response to hypnosis and the response to placebo is particularly interesting. Contrary to what is generally believed, there was no difference in the placebo response between the highly hypnotizable subjects and those who were insusceptible. On the other hand, the relationships between the placebo response and the effect of hypnotic analgesia were very different in these two groups. Thus in the unhypnotizable subjects the response to hypnotically induced analgesia correlated with the response to placebo 0.76, p < 0.01. In the highly hypnotizable group the correlation was totally insignificant, r=0.06. These data strongly support our view that if the hypnotic procedure is expected to he effective by the subject it can exert a nonspecific placebo effect on his response to a painful stimulus. Note that the level of response to placebo in unhypnotizable subjects is, on the average, the same as that to hypnosis. The highly responsive subject, on the other hand, derives more benefit from hypnosis than he does from placebo. Moreover, the fact that the amount of relief yielded is uncorrelated with the amount of relief obtained with placebo in this group strongly suggests that two independent mechanisms are involved.
The placebo effect stems from the patient's belief in the drug's effectiveness, and it follows therefore that any other procedure that, can evoke analogous patient expectancies will produce relief because of the same mechanism. In this sense it is appropriate to speak of a placebo effect of hypnosis that will occur in hypnotizable and un hypnotizable individuals alike, provided they both share the conviction that the procedure will he helpful. We were able to show that the nonspecific effect that is a function of the hypnotic procedure and independent of the patient's response to hypnosis results in a modest but nonetheless highly significant analgesic action. On the other hand, the specific effect of suggestions of hypnotic analgesia in the highly hypnotizable individual will result in a much more profound level of analgesia, which we expect will he additive with the nonspecific placebo component that can occur in all individuals.
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ANOTHER FORM OF COGNITIVE CONTROL OF PAIN
Though we have discussed experimental evidence indicating that there are at least two independent mechanisms in the hypnotic control of pain-the specific effect of hypnotic suggestion and the nonspecific placebo effect-it should also be clear that in a clinical context the use of hypnosis often causes a great many other changes in the dentistpatient interaction which may profoundly affect the patient's reaction to painful stimuli. Rather than bore you with yet another lecture on the importance of the dentist-patient interaction-a lecture which might be mildly interesting but unlikely to be compelling-I would rather have us examine the effect of such changes on pain perception in the context of a once widely used technique: audio analgesia.
In the late 1950s Dr. Wally Gardner' invented a technique to suppress pain. It involved the delivery of high levels of white noise to patients during dental procedures. He had found that increasing the level of white noise stimulation served to prevent the patient's appreciation of pain. This observation was highly congruent with the emerging view that it was possible by flooding the reticular formation with auditory stimuli to block pain impulses from reaching the cortex. The notion that the input to nervous system could be blocked at the periphery as well as at higher levels by stimuli which would interfere with the usual pathways of transmission had. been demonstrated by the pioneering study of Hernandez-Peon, Jouvet, and Scherrer." They recorded the nerve potentials in the auditory nerve of a cat produced by a simple, rapid auditory click. However, when a mouse was presented to the cat, the same click no longer produced the potential changes that had previously been observed. These changes returned once the mouse was no longer present. Thus, it was shown that stimuli originating in the cortex were capable of blocking auditory perception at the level of the cochlea. It was an extension of this concept to the area of pain which ultimately led to the widely known Melzack-Wally gate theory which provided a neurophysiological basis for an understanding of audio analgesia. "'
The observation that white noise seemed to block pain was highly compatible with the view then prevalent within the neurophysiological community that flooding the reticular formation with auditory stimuli could serve to prevent pain impulses from reaching the cortex. The leading consulting group, Bolt, Beranek, and Newman, devoted to the study of sound and its application, evaluated the device for safety and effectiveness and ultimately designed the audio analgesia equip-
224 Trill MECHANISM AND CONTROL OF PAIN
ment offered to the dental profession by the Ritter Company. Here at last appeared to be a safe, nonchemical, scientifically documented procedure for the suppression of pain.
I happened to he working in Boston at that time and was consulted about, and became involved in, some of the early studies of this method. There is no doubt in my mind that the techique was indeed effective. Rather skeptically, I talked with some of Dr. Gardner's patients and then asked him to try the technique on me, at which time I experienced considerable relief subjectively. However, Dr. Gardner was not only impressive as an individual but was also absolutely convinced about the effectiveness of his technique; one could not help wondering whether it was really audio analgesia or whether one had been "Gard-nerized" by his charisma! I However, the technique also proved to be effective in the hands of others.
At the tune I argued strongly against the explanation of audio analgesia primarily in terms of flooding the reticular formation. Instead, I felt that it involved processes partly linked to hypnosis and partly linked to the changes it brought about in the relationship between dentist and patient, giving the latter some control over the behavior of the former. The failure of animal studies to show an effect of white noise on the aversiveness of pain stimuli and related observations eventually supported my conviction that we were not dealing with a straightforward neurological mechanism whereby an intense white noise stimulus blocked pain perception. However, my own views which likened audio analgesia to hypnosis were equally far from the mark insofar as hypnotizability did not seem closely related to an individual's response to audio analgesia. Only much later, after we had begun to understand the distinction between hypnotic effects and placebo effects, slid it become possible for me to more appropriately reconceptualize audio analgesia. To understand this phenomenon, it is necessary to look at aspects which were typically overlooked, but in retrospect can be seen to have been crucially important in making the technique work.
The patient who was to receive audio analgesia was provided with a set of ear phones and a rheostat. Classical music at a comfortable listening intensity was played through the earphones. When one turned the rheostat, white noise would become audible and become increasingly intense as the rheostat was turned until it reached a level where it became quite uncomfortable-though we were assured by specialists that it was still safe. The patient was instructed to relax and listen to the music. However, if he felt any discomfort, he was told that he need only turn up the rheostat, and by making the white noise sufficiently loud,
225 Cognitive Factors in the Control of Pain
he would he able to control any discomfort. A crucial part of the procedure, however, was that the dentist also wore an earphone in one of his ears which indicated, albeit at a lower level of intensity, the level of white noise stimulation chosen by the patient. The patient was told that while he should turn up the white noise sufficiently to block out any pain sensation, once the sensation was at its optimum the white noise should gradually be reduced. As a consequence, the level of white noise tended to track the patient's feeling of discomfort, getting louder as he became uncomfortable and softer as he no longer felt discomfort.
In practice, the level of white noise served as a feedback system for the dentist, indicating when the patient was uncomfortable, and since this typically involved discomfort associated with drilling and the like, the dentist would tend to ease off almost unwittingly as he became aware of his patient's discomfort. While under normal circumstances the level of discomfort for most patients had to be fairly considerable before they would begin to grimace and ask the dentist to stop, the patient's use of white noise ostensibly to control discomfort would serve as an early warning to the dentist that the patient was beginning to find the sensation troublesome, causing him to stop before the stimulus became severely painful. At the same time, the earphones also served other useful purposes. For example, the noise from the dental drill was for most patients the conditional stimulus for the sensation of pain; even when classical music was being played through the earphones, it nonetheless served to diminish greatly the intrusive sound quality of the drill, and even a relatively low level of white noise would serve to shut out the noise of the drill entirely. Those patients who found this to be helpful tended to keep the level no higher than that necessary to eliminate drilling noises. Most important, however, was the fact that turning up the white noise actually served to diminish the discomfort, though this was, of course mediated by the dentist's behavior. As this occurred several times, the patient's confidence in the white noise as an analgesic would increase and it would indeed begin to have an analgesic quality. Finally, the patient had the illusion-partly a correct perception-that he could actually control the level of sensation. Similarly, in laboratory studies subjects will tolerate a higher level of shock if they have control over the stimulus than if they have no such control. At one time, some dental drills were made with a switch which the patient could use to turn off the drill-a device designed to take advantage of the increased pain tolerance associated with the feeling of some control over the stimulus. While this innovation was found useful with some patients, others would interrupt the drilling so frequently that this modification soon became unpopular
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among dentists. The audio analgesia procedure, on the other hand, gave patients the feeling of control while leaving actual control of drilling in the dentists' hands.
It should be noted that it was a number of combined factors in the audio analgesia procedure which caused the patient's pain threshold to go up considerably. A large number of these machines were sold, and many practitioners initially reported considerable success with their use.
In retrospect, one of the important factors which served to convince dentists that this equipment was effective involved what appeared to be a sound neurophysiological explanation of the mechanisms by which pain was suppressed. Dentists using it felt comfortable in assuming that they had a technique which worked on the basis of a straightforward physiological principle. I vividly recall a conversation with a dentist who was very enthusiastic about the equipment and described how effective it was but who was not quite convinced by the gate theory. Consequently, he decided to test it properly, and when patients turned up the equipment, he would increase his drilling activities. It is hardly surprising that he soon found audio analgesia to be worthless. Indeed, as the scientific basis for the use of audio analgesia became less tenable, fewer and fewer dentists chose to employ the procedure. The process that is instructive to note here is that the dentists had paid a goodly sum for the equipment, were initially convinced that its effectiveness had a sound physiological base, and were impressed by patients who were typically highly laudatory concerning its effectiveness; after using the mechanism successfully for some time, however, they became skeptical of the procedure and, I suspect, increasingly aware of the psychological background upon which the success of the technique depended, and consequently began to experience more and more difficulty with the use of audio analgesia.
What are the implications of these findings? It seems clear that the dentist is capable of profoundly influencing the level of patient discomfort by the manner in which he approaches the relationship and by his attention to a number of psychological variables in the manner in which he deals with patients. The audio analgesia procedure would be as helpful to patients today as it was in the early 1960s, provided that dentists were willing to recognize the mechanism by which it works and still use it with conviction since, for the majority-of patients, it is
227 Cognitive Factors in the Control of Pain
effective. It is worth noting that acupuncture, which as yet lacks any meaningful neurophysiological rationale, is seriously considered as a possible treatment procedure though, as Kroger" pointed out, it is a phenomenon closely related to hypnosis and, as Moore and Berk 12 have shown, subjects who are incapable of hypnosis do not tend to profit from acupuncture. However, so long as the mechanism of action is seen as neurophysiological-even if not understood-it is somehow more acceptable than psychological mechanisms which are understood! Indeed, we might consider acupuncture as the Chinese counterpart of audio analgesia.
The history of hypnosis and dentistry reflects the problems to which I have alluded throughout this discussion. The fact that highly responsive subjects are capable of undergoing major surgical procedures without any anesthesia has legitimized hypnosis in the dentists' view as a technique which must have a profound neurophysiological basis, since the notion that such effects may be mediated by psychological mechanisms is simply not accepted as possible by the average dentist. Indeed, it is hypnotic anesthesia that has been the phenomenon which has attracted a goodly number of dentists to the study of hypnosis, which has now become the bridge to the study of psychological influences in dental practice.
Thus, I have tried to explain the paradox that, at most, only 20% of the population are sufficiently responsive to hypnosis to make it possible to carry out major surgery-dental or otherwise-with hypnosis as the sole anesthetic, yet dentists have reported well over 90'% of their patients benefit' from hypnosis. Both observations are correct. Because the dentist who uses hypnosis interacts with his patient in a far more intimate fashion and because the dentist must of necessity attend carefully to the patient's needs if he hopes to have him respond, the entire relationship changes. Further, the dentist who is persuaded to try hypnosis will typically be careful to stop any pain-inducing activity at the first sign of discomfort since he will be very closely attuned to his patients' reaction. This leads to a successful feedback system not dissimilar to that built into the audio analgesia procedure. Finally, the aspect of the patient's behavior which is most troublesome to the dentist is not his response to pain, but rather his phobic response to the fear of pain. Even light hypnosis is usually effective in controlling this type of behavior and in permitting the patient to relax sufficiently to allow suitable local anesthesia to be administered. As a consequence, a modest amount of analgesia makes a world of difference in the patient's subjective experience and resultant behavior in the dental chair.
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While as a scientist I have long sought to understand the hypnotic phenomenon, I believe that the importance of hypnosis for dentistry is not so much as an anesthetic but rather as a compelling demonstration that psychological mechanisms can bring about the most profound changes in fear of pain and pain perception. Once the power of psychological interventions is accepted by the practicing dentist, it will become possible for him to take advantage of a number of cognitive and learning processes which affect the pain experience, and thus will allow him to make dental treatment a more tolerable experience for virtually all of his patients.
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3. James, W. (11111!1). Automatic writing. Prise Ant Soc Psych Res, 1:5413-564. 4. Kaplan, V. A. (1960). Hypnosis and pain. Arch Gen Psychiatry, 2:567-568.
5. ilgard, E. R. (1973). A neodissociation interpretation of pain reduction in hypnosis. Psycho) Rev, 80:396-411.
6. McGlashan, T. H., Evans, P. I., and Orne, M. T. (1969). The nature of hypnotic analgesia and placebo response lo experimental pain Psychosom Med, 31:227-240.
7. Gardner, W. C. and Licklider, J. C. (1959) Auditory analgesia in dental operations, j Am Dent Assoc, 59:1144-1149.
8. Hernandez-Peon, R., Scherrer, I1., and Jun vet, M. (1956). Modification of electric activity in the cochlear nucleus during "attention" in unanesthetized cats. Science, 123: 331-332.
9. Melzack, It. and Walt, 1'. I). (1965). Pain mechanisms: A new theory, Science, 150:971979.
10. Melzack, R., Weisz, A. Z, and Sprague, L.'1'. (1963). Stratagems for controlling pain: Contributions of auditory stimulation and suggestion. Exp Neural, 8:239-247. 11. Kroger, W. S. (1976). Behind Chinese acupuncture-hypnosis? In Pain: Research and Treatment, 13. 1.. Crue (Ed.), Academic Press, New York.
12. Moore, M. and Berk, S. N. (1976). Acupuncture for chronic shoulder pain: An experimental study with attention to the role-of placebo and hypnotic susceptibility. Ann In Med, 84:31H-3114.
The substantive research on which this paper is based was supported in part
by grant #MH 19156 from the National Institute of Mental Health and in part
by the Institute for Experimental Psychiatry.
The preceding paper is a reproduction of the following book chapter (Orne, M. T. Cognitive factors in the control of pain. In L. I. Grossman (Ed.), Mechanism and control of pain. Transactions of the Sixth International Conference on Endodontics. New York: Masson Publishing USA, Inc./Raven Press, 1979. Pp. 213-228.). It is reproduced here with the kind permission of Lippincott Williams & Wilkins; Raven Press is an imprint of Lippincott Williams & Wilkins.