10/21/2025
Melatonin and stress hormones (especially cortisol and adrenaline) have an inverse relationship because they are regulated by opposing systems in the brain. Here’s how it works in simple terms:
✅ Key Reason: Survival Biology
Your body is wired for survival first, sleep second.
When stress or anxiety rises, your brain signals the HPA axis (hypothalamic–pituitary–adrenal system) to release cortisol and adrenaline. These hormones keep you alert and ready to respond to perceived threats.
But melatonin is a hormone that promotes sleep, rest, and darkness signals. High melatonin means "it's safe to rest." So when stress hormones go up, melatonin naturally goes down — because your brain decides it’s not a good time to rest if it believes there is danger.
🧠 The Biological Mechanism
Cortisol and melatonin follow opposite circadian rhythms:
• Cortisol peaks in the morning to wake you up
• Melatonin peaks at night to help you sleep
When you're stressed, cortisol stays elevated into the evening, which suppresses melatonin and disrupts your sleep cycle.
🧩 Simple Example
If your brain thinks:
"I’m stressed, worried, or threatened"
It reacts with:
⚠️ Cortisol up → stay awake
🌙 Melatonin down → no sleep right now
This is why people with chronic anxiety, trauma, or high stress levels get insomnia, especially wired-but-tired energy at night.
🔄 Vicious Cycle
Stress → High Cortisol → Less Melatonin → Poor Sleep → More Cortisol → More Stress → Repeat