Sniffle-busting personalities: positive mood guards against getting colds.

People with generally positive outlooks show greater resistance to developing colds than do individuals who rarely revel in upbeat feelings, a new investigation finds.

Frequently basking in positive emotions defends against colds regardless of how often one experiences negative emotions, say psychologist Sheldon Cohen of Carnegie Mellon University in Pittsburgh and his colleagues. They suspect that positive emotions stimulate symptom-fighting substances.

"We need to take more seriously the possibility that a positive emotional style is a major player in disease risk," Cohen says.

In a study published in 2003, his group exposed 334 healthy adults to one of two rhinoviruses via nasal drops. Those who displayed generally positive outlooks, including feelings of liveliness, cheerfulness, and being at ease, were least likely to develop cold symptoms. Unlike the negatively inclined participants, they reported fewer cold symptoms than were detected in medical exams.

The new study, which appears in the November/December Psychosomatic Medicine, replicates those results and rules out the possibility that psychological traits related to a positive emotional style, rather than the emotions themselves, guard against cold symptoms. Those traits include high self-esteem, extroversion, optimism, and a feeling of mastery over one's life.

The latest data also show that among people with a consistently positive mood, well-being doesn't simply reflect physical vigor. All volunteers entered the study in comparably good health.

In that project, Cohen's team interviewed 193 healthy adults by phone each evening for 2 weeks. The participants reported their positive and negative emotions during that day. They then received nasal drops containing a rhinovirus or an influenza virus that causes a coldlike illness.

Each person was quarantined in a separate room and monitored for 5 or 6 days. Although a positive emotional style bore no relation to whether participants became infected, it protected against the emergence of cold symptoms. For instance, among people infected by the influenza virus, 14 of 50 (28 percent) who often reported positive emotions developed coughs, congestion, and other cold symptoms, as compared with 23 of 56 infected individuals (41 percent) who rarely reported positive emotions.

The extent of positive emotions, but not of negative ones, exerted a strong impact on the emergence of cold symptoms, Cohen says. His recent analysis of immune measures from volunteers in the 2003 study, published last March in Brain, Behavior, and Immunity, points to enhanced regulation of an infection-fighting substance, interleukin-6, in people with positive emotional styles.

Cohen's current study offers "an interesting twist" on the relationship between feelings and health, remarks psychologist Janice K. Kiecolt-Glaser of Ohio State University in Columbus. Other research indicates that negative emotions influence immune function and illness development more powerfully than positive emotions do, Kiecolt-Glaser says.

However, psychologist Barbara L. Fredrickson of the University of North Carolina at Chapel Hill notes that the new data agree with her work showing that to a surprising degree, positive emotions can bolster the immune system to improve health.

Studies of the impact of mood on physical health need to account for both positive and negative emotions, Cohen holds. He points to preliminary data from other teams suggesting that among depressed people, a lack of positive emotions is a more accurate predictor of stroke than is the extent of their negative emotions.