On the mornings she undergoes chemotherapy, Jeanne Safer hypnotizes herself en route in the taxi.

She starts by closing her eyes, then rolling them up to the top of her head and down, all the while breathing deeply. "As I'm doing that, I'm saying to myself, 'This is a procedure that will save my life. I'm not going to fight it. I'm going to make it as easy on my body as possible,' " she said.

Safer, a New York psychologist who has a rare but curable form of leukemia, started out as a skeptic, but found that hypnosis helped put her at ease before biopsies, MRIs and several surgeries. She now uses it with some of her patients as well. "It's an excellent self-management technique," she said. "It gives me a feeling of mastery, a sense that I am participating in my own care rather than just being passive."

Hypnosis has been the subject of fascination, intrigue and ridicule for centuries. Now, researchers are getting closer to understanding why and how it can work. The mechanism may be similar to the placebo effect—in which patients' expectations play a major role in how they feel. Hypnosis, in turn, can help patients adjust those expectations to minimize pain, fear and disability.

The image of a stage hypnotist swinging a stopwatch and commanding a volunteer to squawk like a chicken has led to misunderstandings, experts say. Real hypnosis for therapeutic purposes gives subjects more control over their minds and bodies, not less.

"We can teach people how to manage pain and anxiety, " said Dr. David Spiegel, a psychiatrist and director of the Center for Health and Stress at Stanford University who has studied hypnosis for 40 years. "There's been this mistake in medicine that if you have a certain amount of tissue damage, you should feel this amount of pain. But many things can alter how much pain you feel."

Indeed, scientific evidence is mounting that hypnosis can be effective in a variety of medical situations, from easing migraine headaches to lowering blood pressure, controlling asthma attacks, minimizing hot flashes and diminishing side effects from chemotherapy.

Last week, two studies from Sweden found that one hour a week of hypnotherapy for 12 weeks eased symptoms of irritable-bowel syndrome in 40 percent of patients (compared with 12 percent in a control group) and that the positive effects can last as long as seven years.

Such scientific findings still catch skeptics by surprise—in part because many claims haven't been carefully studied. "Hypnosis is like a good kid with a bad reputation. Everybody is interested, but in the back of their minds, they're thinking of Bela Lugosi," said Dr. Guy Montgomery, director of the Integrative Behavioral Medicine program at Mount Sinai Medical Center in New York who has led many of the studies. "It's not mind control. We can't make somebody rob a bank," he says.

Hypnotherapy does typically begin with the therapist instructing patients to relax deeply—often with long, slow breaths—then focus their attention intently. Some versions have patients imagine being on a beach or in another pleasant setting and enjoying all the sights, sounds and sensations.

Once patients are relaxed and focused, practitioners give them soothing messages and suggestions, such as, "You have no urge to smoke" or "There is nothing to fear." Theoretically, those thoughts remain even after the patient is focusing on the real world again.

However it works, a hypnotic suggestion in the mind can have measurable effects in the body.

One Stanford study asked subjects to imagine that they were eating, and their secretions of gastric acid increased by 70 percent. In a study from Harvard Medical School published in the Lancet in 2000, patients who had 15 minutes of hypnosis before surgery not only needed less pain medication afterward, but also took less time in surgery, saving an average of $331 each.

"There is a strong link to physiology—and it's getting stronger, the more research is being done," said Tanya Edwards, director of the Center for Integrative Medicine at the Cleveland Clinic. She said about half of the center's patients are referred by other Cleveland Clinic physicians, particularly gastroenterologists, oncologists and primary-care physicians looking for ways to help reduce patients' pain.

Brain-imaging studies have shown that while parts of the brain that register painful sensations are still active, the anterior cingulate cortex, which reflects attention, is less engaged. That observed brain effect is greater in the 10 percent to 15 percent people who are "highly suggestible" to hypnosis. About 30 percent of people are resistant—particularly those who are deeply skeptical.

Whether patients are actually in a "trance" is a matter of debate. Montgomery said the notion is upsetting to some people, and he finds that being relaxed and at ease is sufficient to benefit.

Spiegel counters that "you get more bang for your buck if you're in a trance," which he describes as being completely absorbed—like being engrossed in a great book or movie. But he notes that people can enter and exit that state at will.

Experts say there are few harmful side effects to hypnosis, although some hypnotists who claim to help clients "recover" lost memories have been charged with implanting false ones, which can be highly destructive to real relationships.

Finding a hypnotherapy practitioner can be confusing. There are no state regulations for lay practitioners, and the term "certified hypnotherapist" has little meaning, since some groups that issue certificates have very lax standards. (Psychologist Steve E. Eichel caused a stir in 2002 by obtaining hypnotherapist credentials for his cat, Dr. Zoe D. Katze, from several associations.)

Seeking help from a medical or mental-health professional who has a state license in that field and offers hypnosis along with other services is a safer choice, many experts say. Any medical or psychological issues should be fully evaluated before a patient tries hypnosis.

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