[Systemic inflammation, "sickness behavior" and expectations : What role do expectations play in...

Systemic inflammation is accompanied by unspecific physical and psychological symptoms of sickness, including pain and affective symptoms. These symptoms (commonly called "sickness behavior") are mediated by the central nervous effects of immune messengers such as pro-inflammatory cytokines. While adaptive during acute inflammation, sickness symptoms can have detrimental effects on quality of life during chronic inflammation and may contribute to comorbidity in chronic pain conditions. Despite the high clinical relevance of sickness behavior, psychological interventions aiming to modulate sickness symptoms have hardly been investigated. One approach could be the use of expectation effects, since positive and negative expectations (placebo or nocebo effects) have been shown to have an influence on pain and affect-related symptoms.

Herein, we summarize immunological and psychobiological factors that contribute to pain in the context of sickness behavior, with a major focus on findings from experimental endotoxemia. Against this background, we discuss how expectations could help to improve immune-mediated sickness symptoms and outline potential psychological and psychobiological mechanisms underlying this putative effect.