Experimental induction and termination of acute psychological stress in human volunteers: effects on immunological, neuroendocrine, cardiovascular, and psychological parameters.

The present research investigated the effects of controlled experimental manipulations of stress on biological and psychological reactions. Fifty young adult male volunteers were exposed to a 12-min period of stress induced by the threat of an unavoidable, painful electric shock. A 12-min period without this threat preceded or followed the stress period. Blood was drawn during the 4th and the 12th minute of each period. Anticipatory threat led to significant elevations in the proportions and cytotoxic activity of natural killer (NK) lymphocytes, plasma epinephrine levels, pulse rate, and reported level of tension, and to a reduction in the CD4/CD8 ratios. The no-threat period induced a return to baseline values for epinephrine, pulse rate, and tension, and lower than baseline levels for cytotoxic activity of NK lymphocytes, within a similarly short time span. The findings underline the rapidity with which physiological changes may transpire in the course of a brief and acute period of psychological stress, and the rapidity of their reversal upon relief from the stressor.