This is the image many people have of meditation: "You sit in a full lotus posture and pretend you're a Buddha."

So laments Jon Kabat-Zinn, PhD, director of the University of Massachusetts Medical Center's relaxation program. "The real essence of meditative practice," he says, "is how you keep your mind from moment to moment, right through your day."

Meditation, once considered mystical mumbo-jumbo by most Western scientists, is slowly emerging as a legitimate medical treatment.

In clinics around the country, the technique is being used to calm hypertense cardiac patients, soothe the anxiety of chronic pain sufferers and teach coping skills to people with a wide range of stress-related ailments. A 1984 report by the National Institutes of Health recommended that relaxation (a byproduct of meditation), along with salt restriction and weight loss, be prescribed for mild hypertension -- before resorting to drugs. "Stress management" clinics are currently in vogue at several university hospitals, often in conjunction with cardiac rehabilitation programs. Some insurance companies even pick up the tab for outpatient stress reduction/relaxation programs.

"While it's still controversial, people today are far more receptive to the notion that meditation is clinically useful than they were 15 years ago," says Kabat-Zinn.

What brought about this change in meditation's reputation is years of careful research documenting its physiological effects, coupled with the growing acceptance of the psychological components of disease, so-called mind/body interactions.

In the late 1960s, maverick Harvard cardiologist Herbert Benson hooked up heart, brain and skin monitors to practitioners of transcendental meditation (TM) -- a yoga tradition brought to the West in the 1960s by Indian guru Maharishi Mahesh Yogi. He discovered that the act of meditating -- sitting quietly with the eyes closed, silently repeating a sound, word, prayer or phrase, and passively disregarding other thoughts for 15 to 20 minutes at a time -- brings about significant physiological changes: The heart rate slows, the body's metabolism and oxygen consumption are reduced, brain waves shift from an alert beta rhythm to a relaxed alpha rhythm, blood levels of lactate -- a chemical associated with anxiety -- decrease, and blood flow to the muscles declines; instead, blood flows to the brain and skin, producing a feeling of warmth and quiet mental alertness. In short, the body and mind are in a state of deep relaxation.

In his ground-breaking 1975 book, "The Relaxation Response," Benson wrote that, in addition to TM, "any form of mental concentration that distracts the individual from the usual cares and concerns of the mind" -- autogenic training (self-hypnosis), prayer, progressive muscular relaxation -- can evoke the "relaxation response." Practiced regularly, he hypothesized, these techniques can reduce high blood pressure and otherwise counteract the debilitating, health-draining effects of chronic stress -- the frequent activation of the "fight or flight" response, the physiologic opposite of the relaxation response.

(Any perceived threat can activate the fight or flight response: When one does, the sympathetic nervous system responds by secreting hormones that mobilize the body's muscles and organs for defense; the heart beats faster, blood pressure rises, muscles tense and blood flow shifts from the limbs to the organs. The body is now primed to face its attacker or to flee. Usually, however, there is no attacker, simply the everyday worries and pressures of modern life.)

Since the mid-1970s, hundreds of studies -- some good, some not so good -- have been published illustrating the connections between stress and illness, as well as the profound physiological changes associated with deep relaxation. Last summer, the Esalen Institute Study of Exceptional Functioning in Sausalito, Calif., released a massive report that reviews more than 1,000 scientific papers on meditation's effects.

Among the most recent, rigorous and clinically relevant ones, studies by Kabat-Zinn, who is also an assistant professor of medicine at the University of Massachusetts at Worcester, have shown that meditation can help reduce the pain of headaches (including migraines), backaches, arthritis and pain of cancer. About 400 physicians in the central Massachusetts area refer patients to the program, Kabat-Zinn says.

Kabat-Zinn's program consists of an eight-week course that teaches participants -- outpatients with ailments ranging from migraines and panic attacks to heart disease and cancer -- to take better care of themselves; they learn gentle yoga exercises and meditation, both practiced from the perspective of "mindfulness."

Kabat-Zinn says: "Mindfulness involves maintaining awareness in the present moment. Techniques for developing it include scanning the body for sensations and focusing on slow, rhythmic breathing. This has to do with mental training, learning how to relax . . . watch your thoughts and feelings without reacting, as if you were a 'detached observer.' "

According to Duke University Medical Center researchers, relaxation methods also can help people with adult-onset diabetes to regulate glucose and thereby reduce their need for insulin. Benson's associates at the Harvard Medical School have found that regular sessions of a simple meditation technique lowered the body's response to norepenephrine, a stress-related hormone, and mimicked the action of beta-blocking drugs used to control blood pressure. Research by Dean Ornish, director of San Francisco's Preventative Medicine Research Institute, has shown that relaxation training improves blood flow to the heart. Perhaps most provocative are studies conducted by Janice Kiecolt-Glaser and others at Ohio State University revealing that medical students who practiced relaxation had better immune function than those who didn't, and that an elderly population's immune function improved significantly, compared to a control group, after just one month of practicing relaxation techniques.

Patients at another Massachusetts hospital -- Boston's New England Deaconess -- are also learning the practical benefits of meditation and relaxation. Joan Borysenko, a cancer cell biologist, clinical psychologist and colleague of Herbert Benson's, runs the Mind/Body Clinic there.

Like Kabat-Zinn's stress reduction program, the Mind/Body Clinic teaches mindfulness meditation, along with the relaxation response. "We're very interested in people learning to develop the capacity to bring down their autonomic arousal, literally in one or two breaths," says Borysenko, who years ago cured herself of debilitating migraines through meditation. "We focus on breathing and the shift in physiology it produces to create a distance between you and what goes on in your mind. What generally causes us stress is that we become completely caught up in the contents of our minds. We teach people to stop worrying; that helps relieve their symptoms, it reduces their hostility, and it generally improves their lives."

Nearly 2,000 people have been through the Mind/Body Clinic's 10-week program, says Borysenko, who just published a book about the clinic's work called "Minding the Body, Mending the Mind" (Addison Wesley). The mindfulness technique also appears to improve one's memory, Borysenko adds. "By learning to concentrate on what's going on in the moment, people find they can remember more." Across the country, a San Francisco internist and assistant professor of medicine at the University of California Medical Center, Dean Ornish, has undertaken an ambitious study to see if meditation and life style changes can reverse coronary heart disease. He is comparing the health of 25 heart patients who change their life styles for a year to 25 patients who don't change their life styles. The subjects eat a low-fat, low-cholesterol diet; they are given take-home meals, which account for about half of their food, and take special cooking classes to learn how to prepare their own at home. They also practice meditation and yoga for at least an hour a day, and they walk for an hour at least three times a week.

Although the study is not yet over, subjects have already made striking gains, says Ornish. Their average cholesterol level -- an important predictor of heart attacks -- has dropped 39 percent, from 230 to 141 milligrams per 100 milliliters of blood. Even more impressive, their levels of low-density lipoprotein (LDL) cholesterol, the undesirable form, have plummeted an average of 59 percent.

The improvements cannot be credited to meditation alone, because so many life changes are involved in the study. But Ornish believes meditation plays a role. "Most cardiologists still can't believe that stress has much to do with heart disease," he says. "These aren't things we're taught in medical school, you know." But, he adds, such ideas are slowly becoming more accepted.

"I'd say meditation is at the point that exercise was 15 to 20 years ago," Ornish adds. "As more scientific data came out supporting exercise's benefits, doctors themselves began to run and to recommend exercise to their patients. The same thing is starting to happen with meditation."

Eleanor Smith is a free-lance writer in California.