studies on relationships and the common cold

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Under meticulously controlled conditions, [Sheldon Cohen] systematically exposes volunteers to a rhinovirus that causes the common cold. (23) About a third of people exposed to the virus develop the full panoply of symptoms, while the rest walk away with nary a sniffle. The controlled conditions allow him to determine why.
His Methods are exacting. Cohen's experimental volunteers are quarantined for twenty-four hours before they are exposed, to be ure they have not picked up a cold elsewhere. For the next five days (and for $800) the volunteers are housed in a special unit with other volunteers, all of whom are kept at least three feet from one another, lest they reinfect someone.
During those five days their nasal secretions are tested for technical indicators of colds (like the total weight of their mucus) as well as the presence of the specific rhinovirus, ad their blood samples are tested for antibodies. This way Cohen takes the measure of the cold with a precision that goes far beyond counting runny noses and sneezes.
We know that low levels of vitamin C, smoking, and sleeping poorly all increase the likelihood of infection. The question is, can a stressful relationships be added to that list? Cohen's answer: definitely.
Cohen asigns precise numerical values to the factors that make one person come down with a cold while another stays healthy. Those with an ongoing personal conflict were 2.5 times as likely as the others to get a cold, putting rocky relationships in the same causal range as vitamin C deficiency and poor sleep. (Smoking, the most damaging unhealthy habit, made people three times moe likely to succumb.) Conflicts that lasted a month or longer boosted susceptibility, but an occasional argument presented no health hazard. (24)
While perpetual arguments are bad for our health, isolating ourselves is worse. Compared to those with a rich web of social connections, those with the fewest close relationships were 4.2 times more likely to come down with the cold, making loneliness riskier than smoking.
The more we socialize, the less susceptible to colds we become. This idea seems counterintuitive: don't we increase the lieklihood of being exposed to a cold virus the more people we interact with? Sure. But vibrant social connections boost our good moods and limt our negative ones, suppressing cortisol and enhancing immune function uner stress. (25) Relationships themselves seem to protect us from the risk of exposure to the very cold virus they pose.

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(23) Cohen assessed the emotional quality of their social interactions in one of his groups of volunteers in the days before coming into the lab. Unpleasant interactions, especially prolonged conflicts (as with heightened levels of cortisol), predicted that a person would be more likely to come down with a severe cold.

Sheldon Cohen, "Social Relationships and Susceptibility to the Common Cold," in Ryff and Singer, Emotion, Social Relationships, pp 221-44.

(24) Sheldon Cohen, et al., "Sociability and Susceptibility to the Common Cold," Psychological Science 14 (2003), pp 389-95. This study measured social encounters in the weeks before exposure to the rhinovirus, rather than in the day during and after the exposure (since volunteers were in quarantine by then), and so it does not answer the question of whether pleasant or unpleasant encounters just before and on the day of exposure affect immune defenses. That study remains to be done.

(25) Sociability-- seeking out others in friendly, genial way-- was linked to better moods, better sleep efficiency, and lower levels of cortisol, which in turn predicted less risk of a cold. But, Dr. Cohen notes, searching for a more robust connection might show with greater precision how sociability might "get inside the body"-- a question that remains a mystery in need of a more rigorous solution.

Sheldon Cohen, "Psychosocial Models of Social Support in the Etiology of Physical Disease," Health Psychology 7 (1988), pp. 269-97.

Relationships with a spouse, grandchildren, neighbors, friends, fellow volunteers, or fellow religious congregants al preduct that a person will be less susceptible to colds when exposed to rhinoviruses.

Sheldon Cohen, "Social Relationships and Health," American Psychologist (November 2004), pp 676-84.