A tale of two mechanisms: A meta‐analytic approach toward understanding the autonomic basis of cardiovascular reactivity to acute psychological stress

A series of meta‐analyses was undertaken to determine the contributions of sympathetic and parasympathetic activation to cardiovascular stress reactivity. A literature search yielded 186 studies of sufficient quality that measured indices of sympathetic (n = 113) and/or parasympathetic activity (n = 73). A range of psychological stressors perturbed blood pressure and heart rate. There were comparable aggregate effects for sympathetic activation, as indexed by increased plasma epinephrine and norepinephrine, and shortened pre‐ejection period and parasympathetic deactivation, as indexed by heart rate variability measures. Effect sizes varied with stress task, sex, and age. In contrast to alpha‐adrenergic blockade, beta‐blockade attenuated cardiovascular reactivity. Cardiovascular reactivity to acute psychological stress would appear to reflect both beta‐adrenergic activation and vagal withdrawal to a largely equal extent.