Illness expectations predict the development of influenza-like symptoms over the winter season.

<bold>Objective: </bold>This study explores the hypothesis that cognitive expectations of catching influenza-like symptoms increase the chances of developing the symptoms over the winter season.<bold>Design: </bold>Self-reported data from 247 healthy volunteers were obtained twice, before and after the winter season. In the first assessment, expectations about developing influenza-like symptoms in the incoming months were charted. This data was matched with a post-winter assessment of the actual development of the symptoms.<bold>Results: </bold>The odds of developing symptoms were highly associated with the expectations declared months before (OR = 1.776), and the association remained stable (OR = 1.453) even when accounting for previous influenza-like illnesses and the perception of general health. In contrast with previous findings, perceived stress was not associated with symptom development.<bold>Conclusions: </bold>These results support the hypothesis of a self-fulfilling prophecy mechanism related to influenza-like symptoms. [ABSTRACT FROM AUTHOR]