A new study at Carnegie Mellon University in Pittsburgh confirms how college challenges both mind and body, by demonstrating that lonely first-year students mounted a weaker immune response to the flu shot than did other students. The study appears in the May issue of Health Psychology, which is published by the American Psychological Association (APA).

The research team, headed by doctoral student Sarah Pressman and pioneering health psychologist Sheldon Cohen, PhD, also found that social isolation, measured by the size of a student's social network, and feelings of loneliness each independently compromised the students' immunity. Thus both objective and subjective aspects of social life appear related to health.

In the multi-faceted study, 37 men and 46 women, mostly 18-19 years old, were recruited in their first term at Carnegie Mellon. They got their first-ever flu shots at a university clinic and filled out questionnaires on health behavior. For two weeks starting two days before vaccination, they carried palm computers that prompted them four times a day to register their momentary sense of loneliness, stress levels and mood. For five days during that period, they also collected saliva samples four times a day to measure levels of the stress-hormone cortisol.

To assess loneliness, the students took questionnaires at baseline and during the four-month follow-up. Researchers calculated social-network size at baseline by having the students provide the names of up to 20 people they knew well and with whom they were in contact at least once a month.

The researchers assessed blood samples drawn just before the flu shot and one and four months later for antibody levels, which indicated how well the students' immune systems mounted a response to the multi-strain flu vaccine, which included three different antigens.

Sparse social ties were associated at a level of statistical significance with poorer immune response to one component of the vaccine, A/Caledonia, independent of feelings of loneliness. Loneliness was also associated with a poorer immune response to the same strain � as late as four months after the shot. This supports the argument that chronic loneliness can help to predict health and well-being.

The independence of social-network size and loneliness as factors in immunity is supported by the observation that, says Pressman, "You can have very few friends but still not feel lonely. Alternatively, you can have many friends yet feel lonely."

The finding could also help to explain why first-year students tend to visit student health centers more than older classmates; they can be unmoored socially as they adjust to their new circumstances.

Researchers will continue to study these interrelated variables to isolate the specific pathway by which social factors can alter immunity. Among other things, they speculate that stress may be a go-between because loneliness is stressful and stress impairs health. In any case, the findings reinforce the knowledge that social factors are important for health, in part because, says Pressman, "they may encourage good health behaviors such as eating, sleeping and exercising well, and they may buffer the stress response to negative events."