In research at the Harvard Medical School, associates of Dr. Benson found that regular sessions of a simple meditation technique decreased the body's response to norepenephrine, a hormone released in reaction to stress. Although the endocrine system continued to emit the hormones, they did not seem to have their usual effects.  ''Ordinarily, norepenephrine stimulates the cardiovascular system,'' Dr. Benson said. ''But regular relaxation training resulted in less blood pressure increase to norepenephrine than is usually seen. Relaxation seems to mimic the action of the beta-blocking drugs used to control blood pressure.''  Research by Dean Ornish, director of the Preventive Medicine Research Institute in San Francisco, has shown that relaxation training improves blood flow to the heart. Silent ischemia, which chokes off that blood flow, can damage the heart without causing noticeable pain. He also found that relaxation lowered cholesterol levels and lessened the severity of angina attacks.  In 1984, a National Institutes of Health report recommended the use of relaxation, along with salt restriction and weight loss, as the first therapy for mild hypertension, before resorting to drug treatments. Nevertheless, many cardiologists have been slow to use the relaxation techniques.  ''Most cardiologists still can't believe that stress has much to do with heart disease, or that relaxation can help in more than a minor way,'' Dr. Ornish said. ''They don't learn about relaxation techniques in medical school, so they ignore them. But, slowly, relaxation is making more sense to them.'' Diabetes and Chronic Pain  Diabetics can benefit from relaxation, according to research by Richard Surwit, a psychologist at the Duke University Medical Center. In a series of studies, Dr. Surwit found that relaxation improved the body's ability to regulate glucose in patients with the most common type of diabetes, which has its onset in adulthood. It is the body's inability to control glucose, or blood sugar, that ultimately leads to the damage done by the disease.  Relaxation seems to offer relief to many asthmatics by diminishing both the emotional upsets that can trigger attacks and the constriction of air passages that chokes breathing, according to a report by Paul Lehrer of Rutgers Medical School in the current issue of the Journal of Psychosomatic Research. The effects have been more pronounced for those who suffer chronic asthma, rather than those whose asthma is seasonal.  One of the major boons of relaxation training has been in lessening or alleviating chronic, severe pain. Such pain can arise from many different causes, including backache and chronic migraine or tension headaches, diseases such as cancer, and even as the unintended outcome of operations to control pain.  In a recent article in the Journal of Behavioral Medicine, Dr. Kabat-Zinn reported a sharp decrease in pain and related symptoms in patients trained in relaxation at the University of Massachusetts Medical Center in Worcester. The patients in the study, who included the full range of those typically seen in pain clinics, were able to lessen or, in some cases, stop altogether their use of pain drugs.  Four years after their training ended, the majority of patients were still faithful in their use of the relaxation practice, and still reported a decrease in pain and less reliance on drugs to control it, Dr. Kabat-Zinn said.  Relaxation is being used clinically in a much larger range of medical problems than the research so far has been able to assess. These include the management of the side effects of such medical procedures as kidney dialysis and cancer chemotherapy, gastrointestinal problems like irritable bowel syndrome, and insomnia, emphysema and skin disorders. Evaluating Overall Effectiveness  Although clinical successes have been reported in individual cases with these disorders, research is now under way at Harvard and other centers to evaluate the overall effectiveness of relaxation in their treatment.  ''It's not yet clear that relaxation will help with every kind of stress reactivity,'' Dr. Kabat-Zinn said. ''And we've just begun to sort out which relaxation techniques work best with which medical problems. Most may be interchangeable, because of their general neuroendocrine effects, but we do not know yet for sure.''  In research at Harvard, students who were identified as being easily engrossed in thoughts and images were trained in muscle relaxation and then asked to visualize certain specific images. Relaxation alone increased defenses against upper respiratory infections. The added imagery, however, enhanced the effect. The research was done by Mary Jasnoski, a psychologist, who reported the findings at a recent meeting of the Society of Behavioral Medicine in San Francisco.  Although their biological effects are essentially similar, the relaxation techniques are very different. In Dr. Kabat-Zinn's ''mindfulness'' training, for example, patients pay careful attention to the sensations in their bodies, sweeping slowly from head to foot. They do not try to change those sensations, but note them precisely, with a neutral awareness. They are also taught a set of gentle yoga movements and stretches, which they do with the same careful attentiveness. Patients are encouraged to extend a relaxed mindfulness into the rest of their daily lives, especially when stressed.  In progressive relaxation, Dr. Lehrer's patients learn to recognize the often-subtle signals of tension in the major muscles of the body, and to systematically release that tension, leaving their whole body in a state of deep relaxation.  And Dr. Benson has found that for many of his patients the relaxation response can be evoked by their sitting quietly with eyes closed for 15 minutes twice daily, and mentally repeating a simple word or sound. ''Eighty percent of patients choose a simple prayer to repeat,'' Dr. Benson said.  The experts caution that intensive training, followed by regular use of the techniques, may be required before many medical benefits appear. Most training programs last several weeks. And, according to Dr. Lehrer, relaxation may be better when it is taught in person rather than learned from a tape.  The benefits seem to come from the physiology of relaxation rather than from mere suggestion, according to Dr. Lehrer. In a recent study, he found that asthmatic patients who were highly open to suggestions and hypnosis actually benefited the least from his relaxation training.  ''Just feeling relaxed may not be the same as being truly relaxed physically,'' Dr. Lehrer said.  Not everyone is helped by the relaxation training, said Joan Borysenko, who directs the relaxation program for outpatients at Beth Israel Hospital in Boston. ''Some people don't change much, some do a little, some a lot. And there are a few whose lives turn around totally.''
THE simple act of becoming relaxed can have surprising health benefits, new research is showing. In addition to the obvious psychological effects of relieving stress and mental tension, the new findings indicate, deep relaxation, if practiced regularly, can strengthen the immune system and produce a host of other medically valuable physiological changes.   In asthmatics, for example, relaxation training has been found to widen restricted respiratory passages. In some diabetics, relaxation can reduce the need for insulin. In many patients with chronic, unbearable pain, the training has brought about significant relief.   Moreover, the research shows, relaxation may help ward off disease by making people less susceptible to viruses, and by lowering blood pressure and cholesterol levels.