Myths vs facts: Cortisol and sleep

Myths vs. Facts: Cortisol and Sleep Cortisol, the "stress hormone," follows a natural circadian rhythm: high in the morning, low at night. A common myth is that cortisol alone causes sleep problems. In reality, the relationship is bidirectional: chronic stress can elevate cortisol and disrupt sleep, but poor sleep also dysregulates the cortisol axis. Another myth is that cortisol-lowering supplements (e.g., ashwagandha, phosphatidylserine) reliably improve sleep. Evidence is limited and mixed; most studies are small or lack proper controls. For most people, lifestyle measures—consistent sleep schedule, reduced evening light exposure, stress management—are more effective and evidence-based. Genetic variants in cortisol-related genes (e.g., NR3C1) have small effects and do not warrant specific supplement use. If sleep issues persist, a medical evaluation is recommended to rule out underlying conditions like sleep apnea or depression.