The Effect of Circadian Photoreceptors Stimulation on the Stress Response of Subjects with High Anxiety: A Pilot Study

The circadian and stress-realizing systems are interconnected, and the balance of their interaction determines the state of human health. The objective of this study was to investigate the modulating effect of activating the circadian system on heart rate variability in female medical students with high anxiety while performing a cognitive task. After 20 min of adequate stimulation of circadian photoreceptors with a monochromatic blue light, the cognitive task performance resulted in a decrease in sympathetic impact. During the session of monochromatic blue light exposure, a trend of increasing heart rate variability was observed in a state of relative rest (especially in the first 5 min). A comparative analysis of the parameters of the letter cancellation test before and after light exposure revealed a statistically significant increase in the indexes reflecting mental productivity, work accuracy, and concentration of attention. The results suggest an essential physiological role of the human circadian system in modulating the autonomic and psycho-emotional conditions, as well as cognitive functions of individuals with high anxiety. Our findings indicate the possibility of quickly correcting the balance in human systemic regulatory mechanisms using the activation of retinal circadian photoreceptors by blue light.