Brain Check; Scientists are mapping the pathways that link emotion to health. The challenge for the rest of us is to put the discoveries to work.(Cover Story)

Byline: Herbert Benson, M.D., Julie Corliss and Geoffrey Cowley (Benson is the Mind/Body Medical Institute Associate Professor of Medicine at Harvard Medical School and founding president of the Mind/Body Medical Institute in Boston. Corliss is a medical writer at Harvard Medical School. Cowley is NEWSWEEK's health editor. For more information go to health.harvard.edu/NEWSWEEK. Graphic by Josh Ulick)

Imagine you're allergic to the oil of the Japanese lacquer tree--so allergic that the brush of a leaf against your skin provokes an angry rash. Strapping a blindfold over your eyes, a scientist tells you she's going to rub your right arm with lacquer leaf and your left arm with the innocuous leaf of a chestnut tree. The rubbing commences, and before long your right arm is covered with burning, itchy welts. Your left side feels fine. No surprise, until you learn that your left arm--not the right--is the one that got lacquered.

Or imagine that Parkinson's disease has reduced your walk to a shuffle and left your hands too shaky to grasp a pencil. You enroll in a study and receive an experimental surgical treatment, which dramatically improves both your gait and your grip. You're ready to declare it a miracle of modern medicine, when you discover that the operation was a sham. The surgeons merely drilled a small hole in your skull and then patched it.

That thoughts and feelings can affect our health is hardly news. In the span of a few decades, mind-body medicine has evolved from heresy into something approaching cliche. So why is NEWSWEEK devoting this Health for Life report to the mind-body connection? Because the relationship between emotion and health is turning out to be more interesting, and more important, than most of us could have imagined. Viewed through the lens of 21st-century science, anxiety, alienation and hopelessness are not just feelings. Neither are love, serenity and optimism. All are physiological states that affect our health just as clearly as obesity or physical fitness. And the brain, as the source of such states, offers a potential gateway to countless other tissues and organs--from the heart and blood vessels to the gut and the immune system. The challenge is to map the pathways linking mental states to medical ones, and learn how to travel them at will.

That effort is now burgeoning. The U.S. government's five-year-old Integrated Neural Immune Program will spend $16 million on mind-body research next year, and private foundations will spend millions more. Patients aren't waiting passively for the results. Throughout the industrialized world, millions are embracing complementary and alternative therapies that incorporate mind-body techniques. At least 2 million Britons and 1 million Japanese now practice yoga, according to the International Association of Yoga Therapists. In the United States--where yoga has spread from health clubs into hospitals and even shopping malls--one recent survey found that nearly half of all adults now use mind-body interventions. They embrace practices ranging from deep breathing and progressive muscle relaxation to meditation, hypnosis and guided imagery. Close to half of them also said they pray--perhaps the oldest and most basic form of mind-body medicine.

They have plenty to pray for. Modern life is rife with potential stressors, and there is now little question that uncontrolled stress can kill. Harvard physiologist Walter Cannon recognized 90 years ago that when confronted by a threat--physical or emotional, real or imagined--the body responds with a rise in blood pressure, heart rate, muscle tension and breathing rate. We now know that this physiological stress response (chart) involves ...