Wang T, Delahanty D L, Dougall A L, Baum A
Department of Psychology, University of Pittsburgh, University of Pittsburgh Cancer Institute, Pennsylvania 15213-3142, USA.
Health Psychol. 1998 Sep;17(5):428-35. doi: 10.1037//0278-6133.17.5.428.
To assess possible diurnal variations in natural killer reactivity to acute laboratory stressors, this study investigated changes in natural killer cell activity (NKCA) during and after three stressors (mental arithmetic, speech, and the Stroop) at 3 times of the day (08:00, 12:00, and 16:00) in 30 healthy men. NKCA activity increased during mental arithmetic and speech tasks at all 3 times of the day. Change in NKCA was greatest in the afternoon. Differences in the magnitude of mood changes were also observed at the 3 times of day, parallel to immune reactivity. These findings suggest that the dynamics of stress-related NKCA are more complex than previously believed and that time of day may affect the way they are generated or interpreted.
