Positive affect and peripheral inflammatory markers among adults: A narrative review.

BACKGROUND: Previous research suggests that positive affect (PA) may promote health and longevity and that one potential mechanism involves inflammation. However, it remains unclear to what extent PA is associated with specific inflammatory markers and whether such associations are driven by main effects of PA and/or due to PA operating as a stress-buffer.
METHODS: The present narrative review incorporates studies (N = 28) that have examined the association between PA and peripheral inflammatory markers obtained using venous puncture or dried blood spots. We separate results by whether the study tested direct effects or stress-buffering, and by type of inflammatory marker [including C-reactive protein (CRP), and proinflammatory and anti-inflammatory cytokines], also paying close attention to type of PA assessment (state, aggregated state, or retrospective, the latter involving recall over one to two weeks), and study design (cross-sectional, longitudinal, and experimental).
RESULTS: Limited evidence suggests that studies were more supportive of a stress-buffering association, compared to a relatively direct association. When significant direct associations were observed, results suggested that studies using measures of state/aggregated PA exhibited more consistent associations with inflammatory markers than studies using retrospective PA. When significant, higher PA tended to be associated with lower pro- and anti-inflammatory markers, suggestive of lower overall inflammatory load. DISCUSSION: Recommendations for the field and future research are discussed, including the value of utilizing state/aggregated PA measures and of examining stress-buffering mechanisms.