April 1994. UC Santa Cruz. I lie in bed in my campus apartment, exhausted after a week of incessant coughing. Coils of pain compress my head and lymph-swollen neck. Their familiar grip transports me back two thousand miles and an emotional eternity to the winter of 1992-3.

I had visited my parents in Michigan for Thanksgiving that year. I knew then that I was stressed, but I thought my state reflected nothing more than academic anxiety compounded by the painful fraying of a dating relationship. I'd get it under control just as I always had, I was sure.

After I returned home to Wisconsin, where I was in the throes of writing a master's thesis in biochemistry, I got a letter from my physician mom: "Alisa, let me tell you what I saw when you visited. You've lost weight. You've stopped caring for your face and hair. You are dressing in a careless, haphazard manner and wear drab, old clothes rather than your usual bright colors. You don't eat much (yes, we noticed). You cry a lot. Your sleep is restless. These are classic symptoms of depression."

She recognized the start of the problem long before I allowed myself to recognize it. As I read her letter, I thought, No, I was too strong, too disciplined, too healthy to let emotional stress make me sick. But I was wrong. For the next six months, colds, flu, and infections alternated their hold on me.

A relentless string of stressful events strengthened that hold. Two months after my visit with my parents, a truck rammed the back of my car as I waited for a pedestrian to cross in front of me. I was badly shaken, but suffered only a stiff neck. Five days later, I skidded down an icy hill into a tree. The car was totaled and I was hysterical.

"Just calm down, young lady. You'll be fine," the policeman said as he drove me to the hospital to be checked for injuries.

"Now be sure to take extra good care of yourself," he said. "Keep up with your vitamins and get lots of rest. People often get sick after they have an accident--your body is just so upset by the whole thing."

Within a week I was bedridden with one of the most severe flu cases my doctor had seen that year. For the first time in my life, emotional stress yielded major physical symptoms.

Now, I am a victim of this phenomenon for a second time. A new set of stresses has exhausted my body's defenses, allowing a virus to wedge itself into my weakened cells. My body, strained by academic busyness, an overcrowded schedule, and never-ending errands, was already at the breaking point. Then, for two consecutive nights, I pushed myself beyond the limit, driving long distances and getting very little sleep. The next day I had a sore throat. Coughing and congestion soon followed.

Five days after the sore throat started, I went to the UC Santa Cruz health clinic. The nurse took my temperature and blood pressure and asked routinely, "Have you had a fever? Are you coughing up anything? Are your ears bothering you?" No, I said, to all three.

Then she asked a question that, before February 1993, would have made me scoff: "Are you stressed?"

I looked at the floor as my eyes filled suddenly and involuntarily with tears. "Yes," I muttered.

To my relief and comfort, this gentle nurse was not the only one who believed in the invisible connection between mind and body. My doctor, whom I saw later, concurred. "The medical community is realizing that the brain and emotions have a direct line to the heart, stomach, and kidneys," she said. "Many of us are going back to a holistic look at life, rather than dividing the body into different parts and viewing them as independent of each other."

The next day, wanting to learn more about this strange connection between mind and body, yet too sick to go to the library, I logged on to a database of scientific literature from home. There, I learned that researchers studying the phenomenon call their field "psychoneuroimmunology," meaning the study of the link between psychological or environmental stress and the body's immunity to disease. I discovered a spate of new journals in the field: Health Psychology, Somatosensory Research, and Brain, Behavior, and Immunity, to name just three. Psychoneuroimmunology even held a prominent place in the 1993 and 1994 issues of the conservative, prestigious Annual Review of Psychology.

According to these review articles, many scientists during the last decade have become convinced that stress promotes diseases ranging from colds to cancer. Researchers have published hundreds of papers supporting the theory. Despite the controversy that some of these papers have generated, the investigators now generally agree on a basic tenet--the links between stress and health are not mystical and intangible, but are forged by specific proteins, receptors, and hormones. Laboratory studies show that stress alters the body's production of dozens of substances, many of which the body needs to combat viruses, bacteria, and cancers.

Researchers discovered, specifically, that the so-called stress hormones, glucocorticoids, are present at higher levels in people under stress. Glucocorticoids suppress the production of white blood cells, which are part of the body's defense against viruses, bacteria, and the cancerous growth of the body's own cells.

Other studies show that significant events in one's life, such as getting married, having a baby, taking a new job in another city, or losing a spouse or close relative, weaken our defenses even more than everyday high pressures do. One study showed that people who had experienced significant events during the previous year, either joyful or distressing, developed colds more readily than did people under ordinary stress.

Now I better understand my poor health this year. After recovering from the depression and illnesses of last winter, I have been careful to exercise regularly, eat well, and get enough sleep. And yet I have been sick three times in the past five months. Perhaps my immune system has not yet recovered from the events of that dark winter: a broken relationship, oppressive roommate conflicts, the car accidents, the death of a relative, and writing my master's thesis.

Another review article taught me even more about how my body responds to stress. The article discussed a 1990 study of the effects of stress on 13 medical students. The study dealt with a source of stress with which I am all too familiar--final exams. It was the first investigation that traced stress to the molecular level.

The scientists examined the students' white blood cells one month before final exams and again during the exams. They found that when the students' bodies were highly stressed, the white blood cells, which are normally summoned into battle by the presence of a foreign protein in the body, were rendered unable to hear the body's call for help.

Specifically, in the more stressful period, during the exams, the cells contained fewer genetic templates for a protein, called IL-2 receptor, that enables the white blood cells to receive a chemical distress signal from other cells. With fewer templates available, the cells make less of the IL-2 receptor protein, suggesting that the students' immune systems were left poorly prepared to combat invaders.

Though the researchers didn't record whether the students actually developed colds, I've noticed I often get sick immediately following exams. Now I know one reason why.

Other published research suggests that stress might do more than simply make people catch a cold more easily. It may promote cancer. Although the results vary widely depending on which cancer and which stress the investigators examine, many scientists are now convinced that stress promotes or complicates cancer. Some physicians have even reported that patients with malignant breast or skin cancer live longer if their stress is reduced through psychotherapy, counseling, or group therapy.

Other researchers hotly deny that emotional status has anything to do with cancer. They point to studies that show that depressed people are no more likely to develop tumors than those who are not depressed. They also argue that scientists have failed to identify any psychological or personality traits that can reliably predict whether any patient will recover from cancer.

The controversy will doubtless continue for years as researchers refine their understanding of the complex relationships between emotions, stress, and disease. But as I lie in bed today, surrounded by Sudafed, cough syrup, and mugs sticky with the residue of honey-laden tea, I know why I got sick. The connection between stress and disease has become as real to me as the virus that sears my throat and fills my nights with racking coughs.