Date Published: December 16, 2013
Publisher: Public Library of Science
Author(s): Paul Enck, Jochen Hefner, Beate M. Herbert, Nazar Mazurak, Katja Weimer, Eric R. Muth, Stephan Zipfel, Ute Martens, Marcus Gray.
The effects of hypnosis on physiological (gastrointestinal) functions are incompletely understood, and it is unknown whether they are hypnosis-specific and gut-specific, or simply unspecific effects of relaxation.
Sixty-two healthy female volunteers were randomly assigned to either a single session of hypnotic suggestion of ingesting an appetizing meal and an unappetizing meal, or to relax and concentrate on having an appetizing or unappetizing meal, while the electrogastrogram (EGG) was recorded. At the end of the session, participants drank water until they felt full, in order to detect EGG-signal changes after ingestion of a true gastric load. During both conditions participants reported their subjective well-being, hunger and disgust at several time points.
Imagining eating food induced subjective feelings of hunger and disgust as well as changes in the EGG similar to, but more pronounced than those seen with a real gastric water load during both hypnosis and relaxation conditions. These effects were more pronounced when imagining an appetizing meal than with an unappetizing meal. There was no significant difference between the hypnosis and relaxation conditions.
Imagination with and without hypnosis exhibits similar changes in subjective and objective measures in response to imagining an appetizing and an unappetizing food, indicating high sensitivity but low specificity.
Hypnosis is a tool used to induce deep relaxation that has been around since Charcot . Hypnosis has maintained a questionable reputation not only because hypnotic quackery has determined its public appearance and opinion , but also since many different schools and traditions have confused professionals . However, over the last 30 years, hypnotherapy has become a serious therapy in many medical, especially in psychiatric and psychotherapeutic areas, partially because of well-controlled clinical trials showing its efficacy [4-6].
The study was conducted during the summer of 2010. The study protocol was approved by the ethics board of the Medical Faculty Tübingen, and all volunteers gave written informed consent prior to participation.
Our study examined whether hypnosis induces gastrointestinal physiological effects, and if so, whether these effects are specific to hypnosis. Efficacy was examined by hypnotically suggesting eating an appetizing and unappetizing meal, and the specificity tested by using a concentration task as a control condition. While hypnosis was able to induce expected changes in the EGG (specifically a decrease in tachygastria) indicating high sensitivity, similar changes were seen with unspecific relaxation, indicating poor specificity of hypnosis. Susceptibility to hypnosis and “absorption” did not influence the outcome.