Patients with ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) and chronic pain report similar level of sickness behavior as individuals injected with bacterial endotoxin at peak inflammation

Background: Chronic sickness behavior is implicated in ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) and chronic pain but the level of subjective sickness behavior in these conditions has not been investigated or compared to other clinical and non-clinical samples, or to the level in experimental inflammation. Furthermore, the relationship between sickness behavior and self-rated health and functioning is not known in patients with ME/CFS and chronic pain. The aim of the present study was to investigate how sickness behavior in patients with chronic conditions differs from that in individuals with experimental acute sickness, primary care patients, the general population and healthy subjects. In addition, we wanted to explore how sickness behavior is related to self-rated health and health-related functioning. Methods: Sickness behavior was quantified using the sickness questionnaire (SicknessQ). Self-ratings were collected at one time-point in 6 different samples. Levels of sickness behavior in patients with ME/CFS (n ​= ​38) and patients with chronic pain (n ​= ​190) were compared to healthy subjects with lipopolysaccharide(LPS)-induced inflammation (n ​= ​29), primary care patients (n ​= ​163), individuals from the general population (n ​= ​155) and healthy subjects (n ​= ​48), using linear regression. Correlations and moderated regression analyses were used to investigate associations between sickness behavior and self-rated health and health-related functioning in ME/CFS, chronic pain and the general population. Results: LPS-injected individuals (M ​= ​16.3), patients with ME/CFS (M ​= ​16.1), chronic pain (M ​= ​16.1) and primary care patients (M ​= ​10.7) reported significantly higher SicknessQ scores than individuals from the general population (M ​= ​5.4) and healthy subjects (M ​= ​3.6) all p’s ​