The effects of acute psychological stress on circulating inflammatory factors in humans: a review and meta-analysis.

Stress influences circulating inflammatory markers, and these effects may mediate the influence of psychosocial factors on cardiovascular risk and other conditions such as psoriasis and rheumatoid arthritis. Inflammatory responses can be investigated under controlled experimental conditions in humans, and evidence is beginning to emerge showing that circulating inflammatory factors respond to acute psychological stress under laboratory conditions. However, research published to date has varied greatly in the composition of study groups, the timing of samples, assay methods, and the type of challenge imposed. The purpose of this review is to synthesize existing data using meta-analytic techniques. Thirty studies met inclusion criteria. Results showed robust effects for increased levels of circulating IL-6 (r=0.19, p=0.001) and IL-1beta (r=0.58, p<0.001) following acute stress, and marginal effects for CRP (r=0.12, p=0.088). The effects of stress on stimulated cytokine production were less consistent. Significant variation in the inflammatory response was also related to the health status of participants and the timing of post-stress samples. A number of psychobiological mechanisms may underlie responses, including stress-induced reductions in plasma volume, upregulation of synthesis, or enlargement of the cell pool contributing to synthesis. The acute stress-induced inflammatory response may have implications for future health, and has become an important topic of psychoneuroimmunological research.