06 | The effects of motion sickness and social stress on salivary cortisol responses

Cortisol is an indicator of hypothalamic pituitary adrenal (HPA) axis neuroendocrine functioning. Cortisol regulates the body's response to stress and maintains homeostasis and overall health. Investigations of cortisol response often employ psychological stress elicited by the Trier Social Stress Test (TSST). Motion sickness also provokes elevation of cortisol. The aim was to compare the effects of motion sickness versus TSST on cortisol. Healthy participants (16 Males), mean age 35.7 (SD 11.4) years, were tested twice, one week apart in the afternoon. Design was 2-period cross-over counter-balanced for order. Psychological stress was induced by the Trier Social Stress Test (TSST) in front of an interview panel. Motion sickness to moderate nausea was provoked by cross-coupled Coriolis motion on a turntable with head movements (Motion). Salivary cortisol was measured at baseline and 2,15, 25, 60 minutes post-test. Stress/Anxiety and Arousal/Alertness (Stress Arousal Checklist: SACL) were measured in both conditions. Overall rise from baseline in salivary cortisol (M+SD nmol/l) was averaged 15-60 minutes, and was higher for Motion (6.08+7.52) than TSST (2.20+2.87) (p<.05). The cortisol peak for Motion at around 25min was later than TSST at around 15min (p<0.05). The increases in Stress/Anxiety were almost identical for both motion sickness and TSST (p=ns). Arousal/Alertness decreased to a small extent after Motion versus TSST (p<0.05). Although Motion produced similar increases to TSST in subjective Stress/Anxiety, cortisol increased almost three times more with Motion. This may imply an additional stress mechanism for the effects of motion sickness on HPA axis functioning.