Cortisol follows a robust circadian pattern in healthy adults: lowest values occur between midnight and 3am, with a sharp rise in the 30–45 minutes after waking (the cortisol awakening response, or CAR) — a physiologically important signal that mobilises glucose for the day ahead, primes immune readiness, and consolidates memory from the prior night's sleep. From its morning peak, cortisol declines steadily through the day to near-baseline by evening.
Supporting the Curve
- Consistent sleep and wake timing
- Morning bright light exposure (amplifies the CAR)
- Avoiding high stress activities in the 2 hours before sleep
- Phosphatidylserine supplementation — shown to blunt excessive cortisol and normalise the curve
- Managing chronic psychological stressors
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