In their first research collaboration, they sought to measure the effect of psychological stress on the immune system. Although earlier studies had established that trauma and other major stress — like the death of a loved one or prolonged sleep deprivation — weakened the immune system, the Glasers wanted to know if lesser forms of stress, like those associated with the workplace or graduate school, had a similar effect.

The Glasers, who worked at Ohio’s State’s medical school, had ready access to an ample supply of stressed-out students, and so they decided to study the toll exacted by school pressure. They took blood samples from a set of students early in the semester and then did so again in the middle of final exams. The Glasers discovered that the stress of examination time seemed to cause a significant weakening of the students’ immune response: by examination time, the medical students showed a significant drop in so-called natural killer cells, a type of white blood cell that battles viruses and helps prevent cancer.

For their second collaboration, the Glasers turned their attention to domestic strife. They wondered about the role that relationships play in health and about the effects of marital stress, which, like school pressure, can be a source of nontraumatic but chronic strain. In what was to be the first of their many studies on marriage and health, the Glasers recruited 76 women, half of whom were married; the other half were separated or had divorced. The Glasers wanted to identify which married women were in troubled relationships as well as which of the women who were separated or divorced from their husbands were emotionally struggling the most. They did this by using marital-quality scales, types of questionnaires that ask couples to indicate agreement or disagreement with statements like “If I had to do it over again, I would marry the same person” or “We often do things together.” Next, using blood tests, the Glasers measured the women’s immune-system responses, tracking their levels of antibody production and other indicators of immunity strength. The results showed that the women in unhappy relationships and the women who remained emotionally hung up on their ex-husbands had decidedly weaker immune responses than the women who were in happier relationships (or were happily out of them).

Though pleased with this study, the Glasers knew that they had succeeded in taking the measure of marital happiness and health only at a single moment. The couple were also curious to study the effect of marital stress as it unfolded in real time. What happens to the body minute by minute, hour by hour, when couples engage in hostile marital disputes? To find this out, they recruited a study group of 90 seemingly happy newlywed couples. Each couple was hooked up to tubes so that blood samples could be drawn from the pair at regular intervals, and the husband and wife were seated face to face. Obscured by a curtain, the researchers watched the couples on video monitors; nurses took the blood samples. The participants, as they had been prompted to do, discussed their most volatile topics of marital conflict, like housework, sex or interference from a mother-in-law. “You wouldn’t think in a study situation that they would tear into each other,” Glaser, who is now the director of the Institute for Behavioral Medicine Research, told me. “But they get into it.” As expected, the couples who exhibited the most negative and hostile behavior during the conflict discussion showed the largest declines in immune-system function during the 24-hour study period.

These data strongly suggested that marital stress could affect the body in striking ways, but the Glaser team had yet to prove that marital conflict had any truly meaningful or lasting effect on health. Kiecolt-Glaser had an idea for another study that would meet this higher standard. She had read about a strange tool used by her dermatology colleagues: a small plastic suction device designed to leave eight tiny blisters on the arm and allow monitoring of the immune-system response at the wound sites. Kiecolt-Glaser’s proposal was to use this blistering device to measure how quickly or slowly physical wounds healed among married couples who had undergone different levels of marital stress.

The experiment had two phases. Each married couple, after their forearms were subjected to the blistering procedure, were asked to talk together for a half-hour: on one occasion they discussed topics chosen to elicit the couples’ supportive behaviors; on another day, after undergoing the blistering procedures again, they discussed topics selected to evoke conflict and tension and tried to resolve them. Before subjecting others to the blistering regimen, each of the Glasers had the device secured to his or her respective forearm to have his or her skin blistered. The sensation is comparable to “someone gently pinching your arm,” Kiecolt-Glaser told me. Nonetheless, the Glasers knew it would be a tough sell to convince others couples to undergo the blistering procedure as well as two weeks of subsequent monitoring of the wounds as they healed. A study grant allowed them to offer $2,000 in total compensation to any couple willing to take part in the experiment. They managed to recruit 42 married couples for the study.

The results were remarkable. After the blistering sessions in which couples argued, their wounds took, on average, a full day longer to heal than after the sessions in which the couples discussed something pleasant. Among couples who exhibited especially high levels of hostility while bickering, the wounds took a full two days longer to heal than those of couples who had showed less animosity while fighting.