Cytokines and Sickness Behavior

Abstract

Non-specific symptoms of infection and inflammation include fever and profound physiological and behavioral changes. Sick individuals experience weakness, malaise, listlessness and inability to concentrate. They become depressed and lethargic, show little interest in their surroundings and stop eating and drinking. This constellation of non-specific symptoms is collectively referred to as "sickness behavior". In recent years, evidence has rapidly accumulated to demonstrate that the necessary synchrony between metabolic, physiological and behavioral components of the systemic response to infection is dependent on the same molecular signals than those that are already responsible for the local inflammatory response. These signals are pro-inflamatory cytokines, such as interleukin-1, interleukin-6, tumor necrosis factor, and interferons. Sufficient evidence is now available to accept the concept that cytokines are interpreted by the brain as molecular signals of sickness. Sickness can actually be considered as a motivation, that is, a central state that organizes perception and action in face of this particular threat that is represented by infectious pathogens. A sick individual does not have the same priorities as a well one, and this reorganization of priorities is mediated by the effects of cytokines on a number of peripheral and central targets. The elucidation of the mechanisms that are involved in these effects should give new insight on the way sickness and recovery processes are organized in the brain. (PsycInfo Database Record (c) 2022 APA, all rights reserved)