The cortisol awakening response, seasonality, stress and arousal: A study of trait and state influences

Summary 

The aim of this study was to investigate the relationship between the cortisol awakening response (CAR) and two key state variables (morning stress and arousal) and the trait-like variable of seasonality as recent evidence suggests that the CAR is subject to both state and trait influences. The CAR was examined across two consecutive winter days in 50 healthy participants. Participants collected saliva samples in the domestic setting immediately on awakening, then at 15, 30 and 45min post-awakening on the two study days. Concomitant trait and state measures were examined, notably seasonal changeability in mood as a trait, and self-reported stress and arousal as state measures. Although there was correlational stability for measures of the CAR across days, there was a significant difference in the magnitude of the increase in cortisol levels following awakening between the two study days, being greater on the first sampling day. This reduction in the magnitude of cortisol increase was significantly associated with an observed reduction across the 2 days in self-reported arousal assessed at 45min following awakening. Participants reported greater arousal (more alert, active, energetic and stimulated, less drowsy, tired and sluggish) on the first study day than the second. Average CAR across days was associated with seasonality score, greater propensity for seasonal changes in mood being associated with smaller average CAR. High seasonality scorers were also more likely as a group to show a strong association between daily changes in state arousal and CAR. This study supports the view that the CAR is, in part, susceptible to short-term changes in state variables, notably perceived arousal, while observing a novel link between CAR and the trait variable of perceived seasonality. Finally a tentative finding suggests the importance of examining for possible interaction between trait and state effects, evidenced by a significantly greater association between state arousal changes and cortisol response changes in those with high (trait) seasonality.

Keywords: Cortisol, Saliva, Cortisol awakening response (CAR), State arousal, State stress, Seasonality