Infection-induced proinXammatory cytokines are associated with decreases in positive aVect, but not increases in negative aVect

Infection commonly triggers nonspeciWc psychological and behavioral changes including fatigue and malaise, anhedonia, inability to concentrate, and disturbed sleep that collectively are termed “sickness behaviors”. Converging evidence from several lines of research implicate the activities of proinXammatory cytokines as a cause of sickness behaviors. Here we elaborate upon the Wndings of previous research by examining whether infection-associated elevations in local proinXammatory cytokines are associated with increased negative mood and decreased positive mood. One hundred and eighty-nine healthy adults were experimentally exposed to rhinovirus or inXuenza virus during a 6-day period of quarantine. Infection, objective signs of illness, nasal IL-1 , IL-6, and TNF, and self-reported aVect were assessed at baseline and on each of the Wve post-challenge quarantine days. In the 153 persons who became infected following exposure to the challenge virus, daily production of IL-6, but not IL-1 or TNF, was associated with reduced concurrent daily positive aVect. Oneday lagged analyses showed that daily production of all three cytokines was related to lower positive aVect on the next day. All lagged associations were independent of previous-day positive aVect and objective signs of illness (mucus production, mucociliary clearance function). There were no associations between cytokines and negative aVect. Findings support a causal association between pathogeninduced local cytokine production and changes in positive aVect over a 24-h timeline. © 2006 Elsevier Inc. All rights reserved.