Positive emotional style predicts resistance to illness after experimental exposure to rhinovirus or influenza A virus

Objective: In an earlier study, positive emotional style (PES) was associated with resistance to the common cold and a bias to underreport (relative to objective disease markers) symptom severity. This work did not control for social and cognitive factors closely associated with PES. We replicate the original study using a different virus and controls for these alternative explanations. Methods: One hundred ninety-three healthy volunteers ages 21 to 55 years were assessed for a PES characterized by being happy, lively, and calm; a negative emotional style (NES) characterized by being anxious, hostile, and depressed; other cognitive and social dispositions; and self-reported health. Subsequently, they were exposed by nasal drops to a rhinovirus or influenza virus and monitored in quarantine for objective signs of illness and self-reported symptoms. Results: For both viruses, increased PES was associated with lower risk of developing an upper respiratory illness as defined by objective criteria (adjusted odds ratio comparing lowest with highest tertile = 2.9) and with reporting fewer symptoms than expected from concurrent objective markers of illness. These associations were independent of prechallenge virus-specific antibody, virus type, age, sex, education, race, body mass, season, and NES. They were also independent of optimism, extraversion, mastery, self-esteem, purpose, and self-reported health. Conclusions: We replicated the prospective association of PES and colds and PES and biased symptom reporting, extended those results to infection with an influenza virus, and "ruled out" alternative hypotheses. These results indicate that PES may play a more important role in health than previously thought.