What Is the Scientific Evidence for Hypnotherapy?
It is more difficult to ascertain the effectiveness of a therapy like hypnosis than a drug or a pill for one simple reason: it isn’t easy to design a proper
double-blind, placebo-controlled study
of this therapy.
Researchers studying the herb
St. John’s wort
, for example, can use placebo pills that are indistinguishable from the real thing. However, it’s difficult to conceive of a form of placebo hypnosis that can’t be detected as such by both practitioners and patients. For this reason, all studies of hypnosis have made various compromises to the double-blind design. Some randomly assigned participants to receive either hypnosis or no treatment. In the best of these studies, results were rated by examiners who didn’t know which participants were in which group (in other words, blinded observers). However, it isn’t clear whether benefits reported in such studies are due to the hypnosis or less specific factors, such as mere attention.
Other studies have compared hypnosis to various psychological techniques, including
and cognitive psychotherapy. However, the same issues arise when trying to study these latter therapies as with hypnosis, and the results of a study that compares an unproven treatment to an unproven treatment are not very meaningful.
In some studies, participants were allowed to choose whether they received hypnosis or some other therapy. Such nonrandomized studies are highly unreliable; the people who chose hypnosis, for example, might have been different in another way.
Even less meaningful studies of hypnotism simply involved giving people hypnosis and monitoring them to see whether they improved. Studies of this type have been used to support the use of hypnotherapy for hundreds of medical conditions. However, for at least a dozen reasons, such
prove nothing at all, and we do not report them here. The reasons why are discussed in the article
Why Does This Database Rely on Double-blind Studies?
Note, however, that one criticism of open-label studies discussed in that article does not apply here: concerns regarding the placebo effect.
In studies of most medical therapies, researchers must take pains to eliminate the possibility of a
placebo effect. This concern, however, loses its relevance when hypnotism is in question. It isn’t a criticism of a study on hypnosis if an observed benefit turns out to be caused by the power of suggestion. After all, hypnosis consists precisely of the power of suggestion! (The placebo effect is only one of many problems with open-label studies, however. For more information, see the article referenced above.)
Given these caveats, the following is a summary of what science knows about the medical benefits of hypnotherapy.
The Possible Benefits of Hypnotherapy
At least 20 controlled studies, enrolling a total of more than 1,500 people, have evaluated the potential benefit of hypnosis for people undergoing
Their combined results suggest that hypnosis may provide benefits both during and after surgery, including reducing anxiety, pain, and nausea; normalizing blood pressure and heart rate; minimizing blood loss; speeding recovery; and shortening hospitalization. Unfortunately, many of these studies were of very poor quality.
Hypnosis has also shown some promise for reducing nausea, pain, and anxiety in adults and children undergoing
treatment for cancer.
It also may be useful in breast cancer survivors suffering from hot flashes.
Numerous anecdotal reports suggest that
can sometimes disappear in response to suggestion. In three controlled studies enrolling a total of 180 people with warts, use of hypnosis showed superior results compared to no treatment.
In one of these, hypnosis was also superior to salicylic acid (a standard treatment for warts)!
In that trial, hypnosis was also superior to fake salicylic acid, hinting that the power of suggestion with hypnosis is greater than with an ordinary placebo.
Many smokers have tried hypnotherapy to break the habit. While hypnotherapy benefits some smokers, it does not appear to be superior to other methods. In a review of 9 studies, researchers found no consistent evidence that hypnotherapy was better than a 14 other interventions for
And, a more recent trial found that, when combined with a nicotine patch, hypnotherapy was no better than cognitive-behavioral therapy.
A review of 4 randomized trials with 273 patients found hypnotherapy was over 4 times more effective compared to a control in treating nicotine addiction. The patients, however, were only followed for an average of 6-12 months, indicating that hynotherapy may produce short-term results.
has shown some promise for
irritable bowel syndrome
In one trial, 90 people with IBS were randomized to receive hypnotherapy provided by an experienced psychologist or supportive therapy.
In a related second trial, 48 people with IBS were randomized to hypnotherapy with a less experienced psychologist or to a waiting list. In both trials, which lasted three months, those who received hypnotherapy showed an improvement in their IBS symptoms. In another trial, the addition of hypnotherapy to supportive talks and usual care improved IBS symptoms when compared to supportive talks and usual care alone in a randomized trial of 100 adults suffering from severe IBS. Over 54% of patients receiving hypnotherapy had symptom improvement for up to 15 months compared to 25% in the control group.
Hypnotherapy has also been studied for IBS in children.
Fifty-two children with functional (unknown cause) abdominal pain or IBS were randomized to hypnotherapy or standard care. After 3 months of treatment, those in the hypnotherapy group reported less pain. A follow-up study found that these effects lasted for almost 5 years in about 2/3 of the children.
A review of 7 quasi-randomized and randomized trials with 1,213 pregnant women during labor compared self-hypnosis training or hypnosis therapy to no hypnosis. There were no significant differences in the use of pharmocologic pain relief, anesthesia, or spontaneous vaginal delivery in 7 trials with 1,106 women. Hypnosis significantly reduced cesarean section in 2 trials with 562 women, but had no significant difference in 1 trial with 305 women.
Other conditions for which hypnosis has shown promise in controlled trials include the following:
However, the quality of many of the supporting studies is poor, and their results are frequently inconsistent.
Hypnosis is particularly popular as an aid to
weight loss. However, a careful analysis of published studies throws cold water on the belief that hypnosis has been shown to be highly effective for this condition; at best, the evidence only points toward a marginal benefit.
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