Stress appraisal is associated with sympathetic neural reactivity to mental stress in humans

Muscle sympathetic nerve activity (MSNA) responsiveness to mental stress is highly variable between individuals. Although stress perception has been posited as a contributor to the MSNA variability during mental stress, prior studies have been inconclusive. Furthermore, the importance of stress appraisal and coping on MSNA reactivity to mental stress has not been investigated. We hypothesize that appraisal of mental stress as a threat (i.e., perceived demands of stress exceed coping resources) versus a challenge (i.e., perceived coping resources sufficient for demands of stress) would be associated with greater MSNA reactivity. Twenty healthy adults (11 males, 9 females, 21 ± 3 yr, 23 ± 3 kg/m²) participated. Beat-by-beat blood pressure (finger plethysmography), heart rate (electrocardiography), and MSNA (microneurography) were recorded during a 10-min quiet rest followed by the Trier Social Stress Test (TSST). After each phase of the TSST (i.e., speech prep, speech, and mental arithmetic), participants reported threat versus challenge appraisal. Endorsement of a threat appraisal was positively associated with changes in MSNA burst frequency (<i>r</i> = 0.548, <i>P</i> = 0.018), burst incidence (<i>r</i> = 0.599, <i>P</i> = 0.009), and total MSNA (<i>r</i> = 0.697, <i>P</i> = 0.037) during the speech stress period. Moreover, increases in threat appraisal across tasks was associated with elevated MSNA burst frequency (<i>r</i> = 0.531, <i>P</i> = 0.023), incidence (<i>r</i> = 0.512, <i>P</i> = 0.030), and total MSNA (<i>r</i> = 0.727, <i>P</i> = 0.027) responsiveness. These findings support an association between stress appraisal processes and postganglionic sympathetic neural reactivity to psychosocial stress and may partially explain interindividual variability in MSNA responses to mental stress.<b>NEW & NOTEWORTHY</b> The present study investigated the association between stress appraisal and muscle sympathetic nerve activity (MSNA) reactivity to the Trier Social Stress Test. Appraisal of the stress task as a threat (i.e., perceived inability to cope with the demands of the task) was associated with exaggerated MSNA reactivity to mental stress in humans. Threat appraisal is associated with exaggerated sympathetic reactivity to stress, potentially underlying the commonly observed interindividual variability in MSNA responsiveness to mental stress.