Cortisol in Arctic residents is linked to the timing of circadian behavior, with population-specific drivers: Nonnatives integrate both photic and behavioral cues, while the indigenous population relies on behavioral rhythms. MTNR1B polymorphism further modulates cortisol, indicating that environmental timing and genetic background regulate activity of the Hypothalamic-Pituitary-Adrenal axis in extreme photic environments.
Gubin et al. (Wed,) studied this question.