What is worse than being a lonely college freshman? Being a lonely and sick college freshman.

A study at Carnegie Mellon University of 37 male and 45 female first-year students found that those who felt lonely mounted a weaker immune response after they received flu shots.

Previous studies have shown a link between moods and vulnerability to disease and that social isolation can inhibit the body's ability to fight off infections. This new study by CMU health psychologist Sheldon Cohen and colleagues found that college freshman, who may be unmoored socially as they adjust to a new environment, may also suffer these same ill effects.

The finding, published in the May issue of the journal Health Psychology, might explain why first-year students tend to visit student health centers more often than upperclassmen. Researchers from the universities of Pittsburgh, Rochester and British Columbia also participated in the study.