Happiness and other positive emotions play an even more important role in health than previously thought, according to a study published in the journal Psychosomatic Medicine by Carnegie Mellon University Psychology Professor Sheldon Cohen. The paper is available online at www.psychosomaticmedicine.org.

This recent study confirms the results of a landmark 2004 paper in which Cohen and his colleagues found that people who are happy, lively, calm or exhibit other positive emotions are less likely to become ill when they are exposed to a cold virus than those who report few of these emotions. In that study, Cohen found that when they do come down with a cold, happy people report fewer symptoms than would be expected from objective measures of their illness. In contrast, reporting more negative emotions such as depression, anxiety and anger was not associated with catching colds. That study, however, left open the possibility that the greater resistance to infectious illness among happier people may not have been due to happiness, but rather to other characteristics that are often associated with reporting positive emotions such as optimism, extraversion, feelings of purpose in life and self-esteem.

Cohen's recent study controls for those variables, with the same result: The people who report positive emotions are less likely to catch colds and also less likely to report symptoms when they do get sick. This held true regardless of their levels of optimism, extraversion, purpose and self-esteem, and of their age, race, gender, education, body mass or prestudy immunity to the virus.

"We need to take more seriously the possibility that positive emotional style is a major player in disease risk," said Cohen, the Robert E. Doherty Professor of Psychology at Carnegie Mellon.