In the  interest of science, researchers recruited lonely people, infected them with the cold virus, and isolated them in a hotel room to see what happened.

What they learned was indeed interesting: Lonely people felt sicker when they had a cold than did people who were happier with the quality of their friendships.

It didn't matter how many people a study subject knew.  What seemed important was whether people felt lonely, which can happen whether you know a lot of people or only a few.   "High quality relationships can occur within any size social network," the research team wrote.  People who felt lonely said their cold symptoms felt more severe. The researchers did not  measure how sick people actually were.

Christopher Fagundes, a psychology professor at Rice University who is senior author on the new study, said it feeds into growing interest from the National Institutes of Health in "patient-reported outcomes" in addition to the more objective measures that dominate research.

For example, cancer researchers often focus on measures like recurrence or progression, but patients are also very interested in how treatments affect quality of life. In primary-care practices, knowing that patients who are lonely may feel symptoms more intensely could make doctors more likely to address underlying mental-health problems. In the long run, that could reduce the number of times a patient visits the doctor and decrease costs.

"A little bit of prevention on the mental-health side can save massive amounts of money," he said.

The new study, published Thursday in the American Psychological Association's journal, Health Psychology, was part of a parent study investigating the common cold, said Angie S. LeRoy, a Rice graduate student. The study participants were recruited by Carnegie Mellon University. (A University of Delaware researcher, Lisa Jaremka, also was part of the loneliness study.)

The loneliness research analyzed data for 213 study subjects who were given nasal drops containing rhinovirus; 160 of them got sick. Lonely people were no more likely to develop symptoms than less lonely individuals, but they were 38.5 percent more likely to report higher severity of symptoms.

Asked whether quarantining people in hotel rooms for five days might have made them feel even lonelier, Fagundes said the important thing, from a research perspective, was that loneliness was measured before people got sick. The study participants had access to phones and computers.

One thing that may have made them feel better: Study subjects were paid $1,060 for completing the study.