The limited supply of blood in the body is normally differentially routed to the various viscera and skeletal muscles as needed by the action of the AND on the sphincter muscles of the arterioles. The vascularization of the skin is under the exclusive control of the sympathetic division of the ANS. To the extent that both divisions of the ANS are represented in the other regions of the body, they function as antagonists. The effect of the sympathetic system is to put blood into skeletal muscle, while the action of the parasympathetic system is to route it into the viscera.
Although there is conflict in the literature over the issue of whether neutral hypnosis produces any change in the peripheral distribution of blood, the evidence seems consistent that hypnotic suggestions can influence the distribution of blood to the skin and other structures. Many of the effects reported on skin temperature, galvanic skin response (GSR), mammary gland development, and the production and alleviation of skin eruptions are probably explainable in terms of alteration of blood flow to these areas (Barber, 1978c). Timney and Barber (1969) replicated earlier findings that subjects in neutral hypnosis developed a significant increase in oral temperature, while Jackson and Hastings (1981) found no significant difference in oral temperature between hypnotic and simulating subjects. In a second study, they found a marginally greater decrease in oral temperature in high-susceptibility female subjects. By imagining that their hands are in cold or hot water, subjects are able to produce temperature differences of up to 20°F between their two hands. Maslach, Marshall, and Zimbardo (1972) have found that while hypnotized subjects were able to change the skin temperature in their two hands in the opposite direction simultaneously, waking controls were unable to do so. Similar effects have been produced using biofeedback. Piedmont (1981) and Crosson (1980) confirmed that skin temperature is alterable by suggestion under hypnosis, and Raynaud and her colleagues (1984) found that neutral hypnosis did not affect rectal or skin temperature, but the suggestion of the sensation of heat decreased rectal temperature and raised mean skin temperature.
McDowell (1953) reported vasodilation in a subject's leg following suggestions of the leg being immersed in warm water, and Nallapa (1952) reported increasing circulation in a case of Buerger's disease (thromboangiitis obliterans) by hypnotic suggestion. Reiter (1956) reported that suggestions of increasing blood flow to the thyroid gland increased the basal metabolism rate (BMR) to 110, resulting in body weight being reduced to normal in an obese patient.
Hypnosis itself does not affect BMR, but emotions produced by hypnotic suggestions may increase or decrease it (Wallis, 1951; Whitehorn et al., 1932). Posthypnotic suggestions have induced body temperature elevation, but Kline (1957, 1958c) believes that direct suggestions are ineffective and that emotive or hallucinatory suggestions are needed.
Contrary to Pavlov's theory that hypnosis involved vasoconstriction in the cerebrum, Nygard found no difference in cerebral circulation in waking or hypnotized subjects.
The GSR refers to the electrical resistance of the surface of the skin. Skin resistance is lowered by the activity of the sweat glands, which secrete an electrolyte onto the surface of the skin. Crasilneck and Hall (1959) report conflicting studies concerning the effects of neutral hypnosis and suggestions of anesthesia on GSR. Using six subjects, Barber and Coules (1959) found no change in skin resistance during induction and a gradual increase of resistance throughout the remainder of the experiment, which was punctuated by responses to individual suggestions. Since sweating is a response to stress produced by the sympathetic division of the ANS, it is likely that what happens is a function of an individual subject's reactions to suggestions. If the subject views the induction procedure as a relaxing event, he will probably respond with lowered sweat gland activity and a higher skin resistance. If he is apprehensive, either about the procedure in general or about some specific suggestion, he is likely to sweat more and thus have a lowered skin resistance. Often the subject's subjective feeling that he is about to go into an unusual state of consciousness may be enough to frighten him into producing a sudden change in GSR level.
A large variety of skin conditions appear to be affected by hypnotic suggestions. Congenital ichthyosiform erythroderma, a scalelike eruption, has been improved by hypnotic suggestion, and in some cases, results have been reported that were limited to the specific areas of the body to which suggestions were directed (Mason, 1952; Schneck, 1954). Large nevi and warts have been reported successfully treated by hypnotic suggestion (Asher, 1956; Fernandez, 1955; McDowell, 1949). Asher reported 15 out of 25 susceptible patients cured of warts. Barber (1978b) reported a rapid cure in 3 out of 11 patients, but an attempt to limit a cure to warts on only one hand by suggesting an alteration of the blood supply to the warts and "feeling them tingle and dry up" was unsuccessful. Both hands cleared up.
In 1941, Pattie reviewed the literature on blister formation. In a typical experiment of the time, blister development was attempted by telling a subject that he was being touched with a hot iron. Results were mainly negative, and, since many of the cases reported were poorly documented or controlled, there is conflict in the reports. The issue of whether a blister can be produced is still unresolved, but the weight of the evidence is negative. On occasion, erythema or a welt may be produced in a susceptible subject, and these may have been reported as blisters in some studies.
Johnson and Barber (1976) were unable to produce a blister in 40 subjects, although two developed a localized inflammation. One of these reactions was attributed to self-injury, a problem that Pattie noted in this type of research. Evidently some good subjects are so anxious to produce the effect the hypnotist seeks, they will actually injure themselves to produce it. The researcher must be able to observe subjects constantly or make the skin area in question inaccessible to them from the time of the suggestion until the time of observation of effects. Spanos, McNeil, and Stam (1982) age regressed 17 previously burned subjects to the time of their injuries and suggested that a blister was forming. None showed evidence of blister formation or even skin discoloration, but one did develop an elevated skin temperature at the site of the injury compared to the contralateral site.
Barber reports that cold sores can be produced in susceptible subjects by suggestion, and probably even without hypnosis.
Ikemi and Nakagawa (1962), using high school students in Japan who were sensitive to a poisonous plant (similar to poison ivy), had both hypnotized and control subjects touch this plant. Both groups were told that it was not the plant they were allergic to. The vast majority of both groups developed no dermatitis. The study was then reversed; both hypnotized and control subjects were instructed to touch a nonpoisonous plant they were told was poisonous. All subjects in both groups developed a dermatitis from slight to marked. Thus, psychological factors have been demonstrated to affect the course of allergic reactions both with and without hypnosis.
A number of studies suggest that breast size may be increased by hypnotic suggestion. Williams (1974), employing controls for weight gain, phase of the menstrual cycle, and measurement position, reported an average increase of 2 inches in bust size in 13 subjects after 12 weekly treatments involving suggestions of warmth, blood flow, tingling, and so on. Home practice sessions were also employed. Willard (1977) replicated this experiment and reported an average gain of 1.5 inches in nine sessions. Staib and Logan (1977) found these gains were retained after 7 months. Erickson (1977b) reported successful hypnotic breast development in a clinical setting.
Respiration rate can be changed by direct or indirect emotion-producing suggestions (Crasilneck and Hall, 1959). Hypnosis per se probably lowers the respiration rate. Reiter (1956) reports that suggestions of pain, anxiety, and grief increase both the depth and frequency of respiration.
Arterial oxygen level is increased by the induction of a pleasant emotion under hypnosis and decreased by the induction of an unpleasant one (Lovett, 1953a, 1953b). Hypnosis per se decreased the waking levels of oxygen saturation. The blood glucose level is closely related to the level of arousal and can be varied by hypnotic suggestion (Barber, 1961b). Olness and Conroy (1985) found that nine out of eleven children between the ages of seven and seventeen were able to increase tissue oxygen in response to taped suggestions. Eight children were experienced in self-hypnosis; three were not. Of the children successful in this task, only one had no previous self-hypnosis training; two children without this training were unable to increase their tissue oxygen.
Hypnosis has often been reported as a treatment for an asthmatic attack (Franklin, 1957; Solovey and Milechnin, 1957; Van Pelt, 1953). Thome and Fisher (1978) found that high- and medium-susceptibility subjects who were given hypnotic suggestions of experiencing an asthmatic attack were convinced that they had experienced one, though physiological measures failed to "'veal a typical asthmatic pattern. Low-susceptibility subjects were unconvinced of the effect.
In a book published in 1953, the same year that Aserinsky and Kleitman published their paper on rapid eye movements (REMs) in sleeping infants that was to revolutionize concepts concerning the stages of sleep and dream research, Weitzenhoffer concluded that hypnosis resembled a stage of light sleep more than either deep sleep or the waking state. In an early article, Barber (1956a) came to the same conclusion. More recent evidence indicates that EEG records obtained during hypnosis are about the same as are obtained in the waking state or in stage 1 sleep (the lightest stage). The EEG record in stage 1 sleep is identical to a waking EEG record except for the appearance of periodic REMs, which is why this stage is sometimes referred to as paradoxical sleep.
No change in a preexisting alpha level is noted on induction (Dynes, 1947). On the other hand, alpha waves were inhibited in nine out of eleven subjects who were given suggestions for visual hallucinations while under deep hypnosis with their eyes closed. Such disruption in an alpha pattern would normally be produced by a subject either thinking or opening his eyes and permitting a visual pattern to stimulate his occipital cortex.
In addition to being capable of producing deep relaxation of the voluntary muscles, hypnosis may be capable of increasing the capability of muscle. Weitzenhoffer (1951) concluded that hypnotic transcendence of voluntary muscular capability is a valid phenomenon. Mead and Roush (1949) noted a significant increase in strength during hypnosis when measured by an arm dynamometer but not when measured with a hand dynamometer. Watkins (1949) suggests that this enhanced muscular ability may be due to the anesthetic effect of hypnosis on pain and fatigue.
Barber and Calverley (1964e), using 60 female volunteers, found that strength of grip was not increased by hypnotic suggestion or by task-motivational instructions. On the other hand, hypnosis per se depressed weight-holding endurance, but task-motivational instructions, with or without a preceding hypnotic induction, increased endurance. In a review of the literature on the subject in 1966, Barber concluded that hypnosis by itself does not increase either strength or endurance, but motivational instructions increase both—with or without hypnosis. Albert and Williams (1975) examined the effects of posthypnotic suggestions on physical endurance. Endurance was found to be lowered with posthypnotic suggestions of fatigue but not increased with facilitating instructions. Nonhypnotized control subjects were not affected by either suggestion. The Borge ratings of perceived exertion indicated that the subjects subjectively perceived the effects suggested subjects, and a control group. When tested posthypnotically, high-susceptibility subjects given motivating suggestions under hypnosis and subjects given waking motivating suggestions performed equally well and better than control subjects. Low-susceptibility subjects given motivational suggestions under hypnosis and subjects exposed to neutral hypnosis did not improve their performance.
Performance on a pursuit rotor task was significantly improved equally by posthypnotic or waking suggestions (Pearson, 1982).
Abramson and Heron (1950) found a significant reduction in labor time with hypnotic analgesia during childbirth, suggesting that hypnosis may produce a more effective contraction of the uterine muscles, a more effective cervical dilation, or both.
Neutral hypnosis depresses gastric secretion, while emotion-producing suggestions under hypnosis may alter it in either direction (Crasilneck and Hall, 1959). Suggestions of eating a delicious meal increased gastric acidity and secretion in 34 of 36 subjects.
Barber (1965d) makes the point that in most of the studies investigating the physiological effects of hypnosis or hypnotic suggestions, no evaluation was made of the relative effects of the specific suggestions, the positive motivation on the part of the subjects, general suggestions of relaxation, or defining the situation as hypnosis. In cases where these parameters are investigated, he asserts, it is usually found that direct, indirect, or even waking suggestions are effective.