Psychiatrists, medical doctors and psychologists have used hypnosis for more than two centuries to treat pain and illness. Since World War II, it has slipped quietly into the clinical mainstream. It is employed today to combat phobias, control bad habits and enhance performance. But what is the underlying mechanism by which it works? How do suggestions conveyed under hypnosis change what one feels? Scientists have asked these questions for years, and recently an ever-growing corps of dogged researchers has attacked these questions from every conceivable direction — but we still don't know the answers.
Work on how hypnosis affects the brain has been done recently at research hospitals here and in Canada. In each case, scanners detected increased blood flow in relevant parts of the brains of hypnotized subjects who were put through color and pain tests. Skeptics insist this could be due to the power of suggestion.
With weight loss the evidence is conclusive. Psychologist Irving Kirsch of the University of Connecticut has compared all the studies that have been done and has found that hypnosis does help people reduce. But motivation is crucial. "It's like the joke about how many therapists it takes to change a lightbulb," Kirsch says. "The answer is one, but the lightbulb has to want to change."