Physiological Effects of Hypnosis

A number of common effects of hypnotic induction were described under the rubric of signs of hypnosis. If conventional methods of Induction, utilizing suggestions of relaxation and sleep are used, these effects commonly include slight to profound muscular relaxation, with consequent alterations in facial expression and posture, eye closure, and lack of spon­taneous movement or speech. Other usual concomitants of the hypnotic state Include a literalness and specificity in the understanding of suggestions (mak ing it imperative that the operator carefully phrase suggestions) and in some cases the development of rapport, a condition in which the subject ignores all suggestions except those made by the operator. It is tempting to describe reactions that result from the induction of the hypnotic state per se, or so-called neutral hypnosis, as general responses to distinguish them from those made only in response to specific instructions. This, however, would be mis leading; these reactions, like any other obtained under hypnosis, are most likely made in response to suggestions. In the case of these general responses, the suggestions are being made explicitly or implicitly in the sug gestions used for trance induction. If an individual subject interprets the hypnotist's exhortation to "respond only to the sound of my voice" as meaning the institution of a state of rapport, he will develop one; if not, he will not.

Thus, although the present author agrees with Edmonston (1977b) that re laxation is a common concomitant of hypnosis, he disagrees with his thesis that it is the equivalent of neutral hypnosis. It results simply because of the usual way in which hypnosis is induced—by suggestions of drowsiness and relaxation—and is not essential to hypnosis, as demonstrated by the work of Gibbons (1974, 1976, 1979). The equating of relaxation and neutral hyp nosis is another common misconception and was the reason that Swartz (l982), in a review of the first edition of this book, took exception to the author's statement that, by itself, hypnosis is neither helpful nor harmful, since he (as the author), believes relaxation is valuable in tension-related conditions.

In this section we consider what physiological reactions can bemodified by suggestions, direct or indirect. Responses involving the autonomic nervous system (ANS) are of special interest since such responses are normally not under voluntary control and hence cannot be produced directly. However they can probably be altered by the mediating action of thoughts, ideation, or goal-directed fantasies.

Crasilneck and Hall (1959), Gorton (1949a, 1949b), and Barber (1961) 1965) have reviewed the literature on the physiological effects of hypnosis This literature is often in conflict because of the absence of adequate controls, especially in the earlier studies. Thus several studies have reported a decrease in heart rate in neutral hypnosis, while others have reported a rise. Probably both effects occur. Heart deceleration may result from the relaxation instruc-tions used to induce hypnosis and heart acceleration from the idiosyncratic reactions of subjects to the subjective feelings aroused by trance-induction procedures. If the subject is frightened by the prospect of hypnosis, may increase. Gorton (1949a, 1949b) reports that except for a slight low. due to relaxation, cardiac activity is about the same for subjects under hypnosis as it is when they are awake. Cardiac rate is much lower during sleep than in either hypnosis or waking.

Bauer and McCanne (1980b) found no significant differences in decrease in heart rate, alpha activity, skin conductivity, or respiratory rate between six hypnotized female subjects and six female simulators.

Barber (1961b, 1965d) reports that hypnotized and waking subjects can increase or decrease their heart rate in response to specific suggestions to do so, but hypnosis does not enhance this effect. It is not possible to determine whether direct suggestions to vary the heart rate are effective without the help of mediating ideation because it is not possible to control what the subject is thinking. Since the autonomic nervous system (ANS) is not under direct voluntary control, if heart rate is to be controlled by a subject, it probably must be done indirectly by an emotional response to ideation produced gestions. Barber also points out that alterations in respiration rate, which can be made voluntarily, can affect heart rate. However, it is difficult to distinguish the direct effects of suggestions, if any, from the emotional concomitants of mediating ideation, goal-directed fantasies, or simply relaxation.

Barber cites a study by Van Pelt in which the latter appeals to have pro-duced cardiac acceleration in a calm subject while controlling for the level of adrenaline in the blood. Raginsky (1959) produced a cardiac block for a brief period by hypnotic suggestion. He also produced extra systoles in labile jects (Raginsky, 1953). Linton and colleagues (1977) found no evidence concordance of heart rate between subject and hypnotist based on empathy as some have suggested, but found some concordance during induction. Morgan and coworkers (1976) reported that suggestions of heavy work produced no alteration in cardiac rate in either hypnotized or waking subjects, but they were effective in producing an increase in ventilation. Barber found that in neutral hypnosis, muscle tension, measured by electromyograph (EMG), was significantly lower, but pulse rate was unchanged. Hilgard and colleagues (1974) reported a significant difference in heart rate following sug-gestions of analgesia that was unrelated to the amount of subjective pain reduction but no significant rise in heart rate with hypnotically hallucinated Electrocardiogram changes have been reported following emotion-producing suggestions (Bennett and Scott, 1949; Berman, Simonson, and Heron, 1954) Blood pressure is affected by both cardiac rate and the peripheral resis-tance in the arterioles produced by the activity of sphincter muscles under control of the ANS. As in the case of heart rate, neutral hypnosis usually neither raises nor lowers blood pressure, but the relaxation effect may reduce the systolic pressure slightly, and any apprehensions that the subject has may raise it. On the other hand, suggestions can produce marked changes of up to 40 millimeters of mercury systolic pressure and 20 millimeters of mercury effect on the systolic pressure, and suggestions of temperature change primarily affect the diastolic pressure. Suggestions of warmth lower the diastolic pressure, and suggestions of cold raise it. Holroyd, Nuechterlein, and Shapiro 982) found that hypnosis reduced systolic blood pressure when bio-feedback did not, but biofeedback was superior to hypnosis in reducing forehead muscle tension. These effects were independent of subjects' hypnotic susceptibility.

A large number of clinical reports are cited by Crasilneck and Hall (1959) to the effect that bleeding can be increased or decreased by hypnotic sug-gestion, although they report a failure to demonstrate such a relationship experimentally. Some clinical sources describe reduction in bleeding as a concomitant of hypnoanesthesia even in the absence of specific suggestions to this effect. Arons believes that only capillary bleeding can be controlled hypnotically because veins have no sphincter muscles. A research difficulty results from the fact that venous, and certainly arterial, bleeding requires immeditate control, so anything less than immediate and total control over them produced by hypnosis is not likely to be experimentally measurable.