Interleukin-6 levels in relation to psychosocial factors: Studies on serum, saliva, and in vitro production by blood mononuclear cells

Psychosocial factors and interleukin-6 (IL-6) levels are both related to risk of morbidity and mortality. The aim of this study was to investigate how a broad range of psychosocial factors related to levels of IL-6 in different media. Fifty-nine men and women aged 30–65 were recruited from a larger study and selected to cover a broad range of psychosocial status. IL-6 levels were analyzed in serum, in saliva collected at home at three different time points during a day, and in the supernatant of cell cultures stimulated in vitro with lipopolysaccharide. After adjustments for age, gender, self-reported health problems, and lifestyle factors, IL-6-levels in serum were negatively correlated with coping and self-esteem, and positively correlated with cynicism, hostile affect, hopelessness, depression, and vital exhaustion. In saliva samples, at all time points, IL-6 levels were positively correlated to cynicism, and IL-6 levels 30 min after awakening were also positively correlated with hopelessness, depression, and vital exhaustion. After adjustment for age and gender, cynicism, depression, and vital exhaustion were negatively correlated to IL-6 levels in the supernatant of cell cultures stimulated in vitro with lipopolysaccharide, but this effect was lost after control for self-reported health problems and lifestyle factors. In conclusion, we found that IL-6 levels in serum and saliva were negatively related to psychosocial resources and positively related to psychosocial risk factors. These data strengthen the argument that IL-6 is involved in mediating the risk for disease development that has been associated with psychosocial factors.