Hypnotherapy is the use of hypnosis as a medical intervention, usually for the treatment of pain and other subjective symptoms. It remains controversial, primarily because the evidence for its efficacy is not yet compelling, but also because it is poorly understood. This situation is not helped by the fact that it is often characterized as an “alternative” therapy, a label that can “ghettoize” an otherwise legitimate treatment modality.

What Is Hypnosis?

Any meaningful discussion of hypnosis, or any other phenomenon, needs to start with a specific, and hopefully operational, definition.  If we cannot define hypnosis then it becomes impossible to meaningfully discuss it. The problem of definition plagues the science dealing with many so-called alternative therapies, such as acupuncture.  Good science requires controlling for specific variables, so that we can determine which variables are having what effects. If we don’t know which variables are part of the operational definition of a specific therapy, then we cannot conduct proper studies or interpret their results.

For example, with acupuncture, in my opinion the only meaningful definition of this procedure is the placing of thin needles into specific acupuncture points in order to elicit a specific response. Research has shown, however, that acupuncture points do not exist, that placing needles at specific points is not associated with a specific outcome, and even that sticking needles through the skin (as opposed to just poking the skin superficially) does not correlate with outcome. When these variables are isolated they do not appear to contribute anything to efficacy, therefore one might conclude that acupuncture does not work. Research into acupuncture, however, often does not adequately isolate these variables from the therapeutic ritual that surrounds acupuncture, or even mixes in other modalities, such as electrical stimulation.

Psychologically-based therapies all suffer from this potential failing as well. It is difficult to separate the variables that are specific to a treatment from the non-specific elements of the therapeutic interaction.

What, then, are the variables specific to hypnosis that make it an identifiable intervention? This is not clear, but we can start with a definition of hypnosis based upon our current understanding. Hypnosis, first of all, is not what happens on stage for the purpose of entertainment. It is not about making people act like a chicken. It is also not a deep sleep or trance-like state. Hypnosis, however, is believed to be a specific state of consciousness. We experience different states of consciousness all the time, defined by differences in alertness and focus of attention. Hypnosis, rather than being a sleep-like state, is actually a state of heightened alertness. Attention, however, is focused (usually on the hypnotist or something they are using as a focus of attention). In this state subjects are more responsive to social cues and suggestion.

The above description of hypnosis is fairly superficial, and is still a matter of ongoing debate. There are conflicts between the conceptual definition of hypnosis (what we think is going on in the brain) and the operational definition (how we define it experimentally). Some researchers suggest that the operational definition is simply increased suggestibility following a hypnotic induction procedure. Even this stripped down definition has problems as it is not clear if hypnosis depth scales are just measuring baseline suggestibility, rather than a hypnosis effect.

My understanding of the current state of the research is that the hypnotic induction procedure may place subjects in a state in which they are focusing their conscious attention and are more receptive to unconscious processing of information (suggestibility). Beyond this there are many theories as to what is going on in the brain, but at present we simply do not really know and much more research is needed. There is no consensus as to the theoretical model of hypnosis. This makes clinical research into hypnosis difficult.

Hypnosis as Therapy

Regardless of the conceptual definition of hypnosis, if we have a standardized operational definition then we can study its effects. Systematic reviews of hypnosis for specific indications, however, generally observe heterogeneity of operational definition of hypnosis across trials. In other words — there often is no consistent operational definition of hypnosis and this makes it difficult to interpret study results. This is another way of saying that clinical research often does not adequately control for variables that allow us to isolate something that can meaningfully be called “hypnosis.”

This is all another way of saying that effects seen from hypnosis may all be either placebo effects or non-specific effects from the therapeutic interaction, rather than a specific response to hypnosis itself.

A systematic review of hypnosis for fibromyalgia pain, for example, found that:

The significant effect on pain at final treatment was associated with low methodological and low treatment quality.

CONCLUSION: Further studies with better treatment quality and adequate methodological quality assessing all key domains of FMS are necessary to clarify the efficacy of H/GI in FMS.

Studies used variable definitions of hypnosis and control of what exactly was being delivered, and poor study quality correlated with positive outcome — a trend that always calls into question whether or not there is a real effect present.

Other systematic reviews of hypnosis for pain control generally find positive effects, but they do not always carefully assess for methodological quality (such as for cancer pain). A systematic review of hypnosis for labor pain also found positive effects, but also cited methodological limitations in the research.

The major limitation of much of this research is that it does not adequately control for the effects of relaxation, cognitive therapy, expectation, or the introduction of a novel therapeutic intervention — all phenomena that may “come along for the ride” with hypnotherapy but not be specific to hypnotherapy. In other words — is hypnotherapy a necessary component of a positive therapeutic effect or is it an unnecessary ritual by which other non-specific elements have an effect? Some researchers are trying to tease apart these variables, but that constitutes a minority of the clinical research on hypnotherapy.


My personal current summary of the clinical research is that there is a suggestion of a positive effect from the specific operational elements of hypnosis (specifically increased suggestibility) for the treatment of subjective symptoms, like pain and nausea, that are amenable to suggestibility. However, the research has not yet adequately isolated this variable and therefore more research of better methodological quality is necessary to definitively answer this question. Until then hypnotherapy will remain controversial.

The more basic question as to what hypnosis is also is in an early stage of research, although there do seem to be some promising conceptual theories. The use of fMRI and other techniques may help define hypnosis from a neuroanatomical perspective, and this may further aid in understanding what hypnosis actually is.

Meanwhile, I find it counterproductive to lump hypnosis in with the broad and poorly defined category of “alternative” therapies. A recent article on hypnotherapy, for example, contained this quote from a practitioner:

“You can think of it in the same general healing family as acupuncture, massage [or] Chinese herbs,” he said. “All of these are kind of nonmainstream or alternative or holistic treatments. But they are gaining much more respect and popularity every year in our country. These are things they’ve been doing in China or India for thousands of years.”

You can see how this approach causes only confusion. Hypnotherapy has not been used in China or India for thousands of years, and has absolutely nothing conceptually in common with any of the modalities mentioned. The only possible connection among these various treatments that would put them into a common “alternative” group is the lack of scientific support or the confusion of placebo effects for specific effects. This is exactly what I meant by the “ghettoizing” of hypnotherapy.

It would be unfortunate for this to happen. I would rather see hard scientific research to better define hypnosis and its therapeutic potential.

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the president and co-founder of the New England Skeptical Society, the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also contributes every Sunday to The Rogues Gallery, the official blog of the SGU.