Placebo and hypnosis

Etzel Cardeña
Center for Research on Consciousness and Anomalous Psychology (CERCAP), Department of Psychology, Lund University

Irving Kirsch
Program in Placebo Studies, Harvard Medical School

Keywords: placebo, hypnosis, hypoalgesia

Definitions of placebo often disparage it as a procedure to humor a patient. The American Heritage English Dictionary (2022) provides a better description: “A substance that has positive effects as a result of a patient’s perception that is beneficial rather than as a result of a causative ingredient” and points out that placebo may be used as a control condition when researching the effectiveness of a medical procedure. The “placebo effect” represents the actual effect of the substance or procedure, which can vary from none to substantial, and be positive or negative (“nocebo”).

Placebo effects vary depending on procedure used, neurotransmitter site affected, and so on (Kirsch, 2018). Placebos can be effective even when the person knows that s/he is receiving an inert treatment (i.e., open-label placebo; Carvalho et al., 2021), and their effects depend on the condition treated (e.g., larger effects for major depressive disorder than for schizophrenia; Bschor et al., 2024).

Research has evaluated potential links between the placebo effect hypnotizability, and hypnotic techniques. Earlier studies evaluating hypnotizability and placebo response found that a correlation between the two may be at most modest and become non-significant when controlling for other variables (reviewed in Sheiner et al., 2016). A more recent paper with two studies found that a significant placebo response did not correlate significantly with hypnotizability in the first one, whereas in the second a non-significant placebo effect correlated significantly with non-hypnotic suggestibility (Parsons et al., 2021). There was a similar, equivocal pattern when evaluating a placebo sedative and hypnotizability. In one study, hypnotizability predicted drowsiness but not physiological responses such as heart rate (Sheiner et al., 2016), yet a similar design could not replicate that relation (Lifshitz et al., 2017).

Another line of research has compared the effectiveness of placebo and hypnotic interventions, usually in regard to pain. In an early study, McGlashan et al. (1969) tested high or low hypnotizables and found that hypnotic analgesia was greater than placebo for high hypnotizables (who did not respond to placebo), whereas low hypnotizables responded modestly and similarly to both hypnotic analgesia and placebo. They concluded that there are two components in hypnotic analgesia: a nonspecific placebo effect, and a hypnotic perceptual distortion effect. Milling et al. (2005) reported that the effects of placebo was better than no-treatment and equivalent to hypnoanalgesia when it followed the hypnotic suggestion, not when it preceded it.

For a different condition (wart removal) a study found that although at first placebo and hypnotic procedures were similarly effective, at six-weeks only the hypnosis condition showed a better outcome than no treatment (Spanos et al., 1990). Considering that for various psychological and medical conditions hypnotic techniques are effective and may produce similar (or better) effects than placebo, Kirsch (1999) advocated using them as a nondeceptive strategy. Yet, it is clear that the relation between hypnosis and placebo is an under-researched area. Programmatic lines of research need to test complex models of placebo and hypnotic interactions before we can gain a clear understanding.

References

The American Heritage Dictionary of the English Language, Fifth Edition (2022). HarperCollins. https://ahdictionary.com/word/search.html?q=placebo

Baker, S. L., & Kirsch, I. (1993). Hypnotic and placebo analgesia: Order effects and the placebo label. Contemporary Hypnosis, 10, 117–126. Retrieved from http://psycnet.apa.org/psycinfo/199416344-001

Bschor, T., Nagel, L., Unger, J., Schwarzer, G., & Baethge, C. (2024). Differential Outcomes of Placebo Treatment Across 9 Psychiatric Disorders: A Systematic Review and Meta-Analysis. JAMA psychiatry, e240994. Advance online publication. https://doi.org/10.1001/jamapsychiatry.2024.0994

Carvalho, C., Pais, M., Cunha, L., Rebouta, P., Kaptchuk, T. J., & Kirsch, I. (2021). Open-label placebo for chronic low back pain: a 5-year follow-up. Pain, 162(5), 1521-1527.

Kirsch, I. (1999). Clinical hypnosis as a nondeceptive placebo. In I. Kirsch, A. Capafons, E. Cardeña, & S. Amigó (Eds.), Clinical hypnosis and self-regulation: Cognitive-behavioral perspectives (pp. 211-226). Washington, DC: American Psychological Association. https://doi.org/10.1037/10282-008

Kirsch, I. (2018). Response expectancy and the placebo effect. International review of Neurobiology, 138, 81. https://doi.org/10.1016/bs.irn.2018.01.003

Lifshitz, M., Sheiner, E. O., Olson, J. A., Thériault, R., & Raz, A. (2017). On suggestibility and placebo: A follow-up study. American Journal of Clinical Hypnosis, 59(4),385–392.

McGlashan, T., Evan, F., & Orne, M. T. (1969). The nature of hypnotic analgesia and placebo response to experimental pain. Psychosomatic Medicine 31(3), 227-246.

Milling, L. S., Kirsch, I., Allen, G.J., & Reutenauer, E.L. (2005). The effects of hypnotic and nonhypnotic imaginative suggestion on pain. Annals of Behavioral Medicine, 29, 116-127. https://doi.org/10.1207/s15324796abm2902_6

Parsons, R. D., Bergmann, S., Wiech, K., & Terhune, D. B. (2021). Direct verbal suggestibility as a predictor of placebo hypoalgesia responsiveness. Psychosomatic Medicine, 83(9), 1041–1049. https://doi.org/10.1097/PSY.0000000000000977

Spanos, N. P., Williams, V., & Gwynn, M. I. (1990). Effects of hypnotic, placebo, and salicylic acid treatments on wart regression. Psychosomatic Medicine, 52(1), 109–114. https://doi.org/10.1097/00006842-199001000-00009