The effects of stress and relaxation on the in vitro immune response in man: a meta-analytic study

The purpose of the present meta-analytic study was to combine and integrate the results of stress and relaxation studies for their reported changes in the in vitro immune response. Twenty-four stress studies and 10 relaxation studies with a (quasi)-experimental design with pre- and postintervention measurements were selected. Twenty immunological variables tested in stress studies and five immunological variables tested in relaxation studies could be further analyzed. The meta-analysis of the results of the stress studies indicated that the observed changes in interleukin-2 receptor expression on lymphocytes and antibody titers against Epstein Barr virus (EBV) were consistent for the direction of change and globally significant, whereas the observed changes in percentage of natural killer (NK) cells, salivary immunoglobulin A (sIgA) concentration, and antibody titers against Herpes simplex virus (HSV) were not consistent and not significant. Analysis of the results of the relaxation studies indicated that the observed changes in sIgA concentration were consistent for direction of change and significant, the results for white blood cell count were consistent but not significant, and the results for percentage of monocytes were neither consistent nor significant.