That's according to a study by Sheldon Cohen, Ph.D., and colleagues. Cohen is the Robert E. Doherty Professor of Psychology at Carnegie Mellon University in Pittsburgh.
"We need to take more seriously the possibility that positive emotional style is a major player in disease risk," Cohen's team writes in Psychosomatic Medicine.
Of course, anyone can get sick. Happiness isn't a magic bullet that guarantees health, and the researchers aren't blaming illness on negative emotions. But the effect emotions have on health may be more complicated than previously thought, the researchers note.
Cohen and colleagues studied 193 healthy adults aged 21-55 (average age: 37). Participants got medical checkups and completed surveys on their emotional style.
Positive emotional-style traits included being lively, happy, or calm. Negative traits included being tense, anxious, sad, depressed, angry, or hostile.
Participants noted how often they had experienced those emotions in the previous two weeks. The goal was to gauge their typical mood, not temporary ups and downs.
Based on the surveys, the researchers gave participants scores for both positive and negative emotional style.
Positive emotional style scores were low for 64 people, medium for 64 other participants, and high for 65 people. Meanwhile, negative emotional style scores were low for 66 people, medium for 62 people, and high for 65 people.
With the participants' consent, the researchers exposed them to viruses that cause colds or flu. The participants were then quarantined for five to six days to see who got a cold or flu.
People with high scores for positive emotional style were more likely to resist colds and flu, the study shows. But people with high scores for negativity weren't especially vulnerable.
In other words, being positive was a plus against colds and flu, but negativity wasn't a hazard.
It's not clear why or how happiness guarded against the diseases.
The study only covered colds and flu. But the findings may have broader meaning.
"These results indicate that positive emotions play a larger and more important role in disease risk and health complaints than previously believed," the researchers write.
For instance, they note that depression is a mix of high negative emotions (like sadness) and low positive emotions (like happiness).
Most research on depression and health has focused on high negative emotions, not low positive emotions, the researchers write.
SOURCES: Cohen, S. Psychosomatic Medicine, November/December 2006; Vol. 68: pp. 809-815. News release, Carnegie Mellon University.
By Miranda Hitti
Reviewed by Brunilda Nazario