Last updated: Thu, Aug 1, 2024
Pain relief as a result of hypnosis provides another tantalizing line of evidence for the role of the mind in pain.
The American Psychiatric Association, it turns out, isn't completely clear about what is going on in hypnosis. They define hypnosis as a procedure in which the subject is guided by the hypnotist to experience changes in subjective experience, thought, or behavior. The Association also recognizes the possibility of self-hypnosis. Studies of hypnosis have found that several elements are involved in hypnosis: 1) a feeling of mental relaxation; 2) sustained attention to a small number of mental "targets"; 3) a perceived absence of judging, monitoring, and censoring on the part of the subject; 4) the sense of automaticity, again on the part of the subject.1
Although hypnosis is accompanied by a feeling of relaxation, electroencephalograms (EEGs) show that subjects in a state of hypnosis experience elevated theta waves, which indicate increased attention. PET studies show increased activity in the cortex, thalamus, and brain stem. Such studies show that networks responsible for vigilance, attention, and self-agency are unusually active during a successful hypnotic experience.2
In guided hypnosis for pain reduction, the hypnotist provides "suggestions" to the subject. A suggestion might be that the subject's sensations are pleasant or neutral rather than unpleasant; that the subject's pain is not threatening or harmful; that the pain is not pain (for example, it may be warmth instead of pain); or that the pain is less intense or altogether absent. Suggestions of these sorts have been used to reduce the aversiveness of painful stimuli in pain hypnosis research.
The effectiveness of the process varies depending on the subject. It is said that 30% of people are highly hypnotizable, 30% moderately, 30% less, and 10% not at all.3 Different suggestions are effective for different people and in different situations. Finally, it is more difficult to lighten intense pain with hypnosis than it is to lighten less-intense pain. (This is in contrast to placebo, which seems to be more effective with more severe pain.)
Theories to explain hypnotic suggestion aren't well-developed or broadly accepted. Some theories rely on a model of the mind that has an executive control function that corresponds roughly to the Freudian idea of the "ego." According to such theories, the subject under hypnotic influence introduces "alternative representations" that compete with and, if successful, displace the problematic representations of reality that include plain old pain. The increased activation seen in various pathways of the mind under hypnosis would then reflect the "psychic energy" (work) needed to displace the plain old pain.4 One might wonder why the pain-plagued subject would not muster these representations and energies on his or her own—that is, why is the hypnotic process necessary? Why is the hypnotist critical to the process? There are many questions unanswered.
Whereas placebo analgesia involves the endogenous opioid-based pain modulating system, hypnotic analgesia appears not to require it. Several studies have shown that hypnotic analgesia isn't defeated by injection of opioid-defeating naloxone.5 Studies that have looked at the signals arriving in the somatosensory cortex during hypnosis of individuals subjected to pain have shown that these signals are reduced. Whatever mechanism is responsible for hypnotic analgesia reduces the amount of pain information that reaches this sensory center and reduces subsequent processing of pain information in the brain.6 This effect extends to the spine, as seen in another study that showed reduced spinal reflexive response to pain in those who responded to hypnotic analgesia.7 Numerous studies have shown that, even when hypnotized subjects deny feeling pain, their heart rate and blood pressure increase as in those who do feel pain.8
The effectiveness of hypnotic treatment for pain depends on the subject, the hypnotist, and the hypnotic routine used by the hypnotist. While there can be strong effects with highly-hypnotizable subjects, they vanish to nothing with the least-hypnotizable subjects. In induced pain (that is, pain caused intentionally in the lab), a reduction in stronger pain requires a more-hypnotizable subject. In one study, hypnotic pain reduction was achieved if the hypnotist maintained contact with the subject throughout the process, but not if this contact was not maintained.9 Some people can be hypnotized effectively enough to undergo dental treatment or even major surgery under hypnosis alone.10
Melzack and Wall related a study of a "fakir" who was able to pierce his own body while in a trance state. He required two hours of intense concentration, after which he reportedly thought about nothing. Once in his trance, his EEG showed increased theta wave activity and heightened sympathetic nervous system activity, just as is the case with hypnotized subjects in hypnotic analgesia studies. Once in his trance, he could repeatedly pierce his body without bleeding and with no sign of pain.11
These characteristics of hypnosis call to mind the Mindfulness Meditation techniques advocated by Jon Kabat-Zinn and many other pain care providers.12 Whatever is going on here, these phenomena indicate that pain is not a simple, invariable process. Our minds, perhaps with additional help from outside, perhaps on their own, are sometimes able to tune in or to tune out or otherwise modify pain signals. Bear in mind, however, that, like the placebo analgesia research, most of what is known scientifically about this has been learned in a lab environment in which pain is meted out in carefully-measured non-harmful doses of very brief duration when compared to typical chronic pain. The limits of these phenomena aren't well understood.