Effects of psychological stress on neutrophil phagocytosis and bactericidal activity in humans--a meta-analysis

Several authors have reviewed the effects of psychological stress on lymphocyte activity. However the effect of psychological stress on neutrophil functions has not been reviewed. The present meta-analysis summarizes evidence of the effects of psychological stress on neutrophil phagocytosis and bactericidal activity collated from a MEDLINE search of the English literature. We searched the database to identify the relevant studies through April 30, 2013. Eleven studies met our inclusion criteria and we divided them into those addressing transient acute stress (3 studies, n=74), academic examinations (4 studies n=101) and chronic stress/life events (4 studies, n=193). We performed a meta-analysis of the data and calculated total standardized mean differences (SMD) to evaluate the effects of chronic stress. Transient acute stressors might both enhance and decrease these neutrophil functions. Academic examinations tended to elevate neutrophil functions. On the other hand, the total SMDs of neutrophil phagocytosis and bactericidal activity altered by chronic stress/life events were -0.589 (95% CI: -0.908 to -0.270, p<0.05) and -0.547 (95% CI: -0.845 to -0.248, p<0.05), respectively, indicating suppressive effects on these neutrophil functions. Further systematic review of more pooled studies is warranted to confirm that academic examinations might enhance, whereas chronic stress/life events might suppress these neutrophil functions.