The Effect of Circadian Rhythm on Cortisol and Perceived Stress Correlations

Stress is a known trigger of the Hypothalamus-Pituitary-Adrenal (HPA) Axis which leads to the production and secretion of the catabolic steroid cortisol by the adrenal gland. Since cortisol production is affected by stress, it follows that a high self-perception of stress would be correlated with high blood and saliva cortisol levels. Literature generally shows a gap in identifying this correlation, perhaps because of the interconnected nature of endocrine pathways. New experimental methods that control for the effects of circadian rhythm have shown limited success in demonstrating this correlation. Our purpose is to continue exploring the relationship between cortisol, perceived stress, and circadian rhythm. This will be done by comparing the results of the Trier Inventory for Chronic Stress (TICS) survey, to the cortisol concentration in saliva samples taken during the cortisol awakening response (CAR). When these results are analyzed, based on individual chronotype (whether someone is a morning or evening person based on the Lark or Owl Questionnaire), we hypothesize that a stronger, positive correlation between perceived stress and cortisol concentration change will be exhibited. When the salivary cortisol concentration changes, during the CAR, were compared to participant perceived stress and chronotype, no statistical significance was determined. Despite conflicting correlative trends, based on comparing results from different time points during the CAR, this research has shown evidence towards a negative correlation between perceived stress and CAR reactivity, and parallel correlative trends between perceived stress and chronotype