Morning Light and the Cortisol Rise

You keep hearing 'get morning light' and it sounds too small to matter. It isn't. It's the only free intervention with this much evidence behind it.

What the researchers actually did

Scheer and Buijs exposed healthy participants to bright light early in the morning and measured the effect on the cortisol response, while Czeisler's group established the dose-response relationship between light intensity, timing, and the resetting of human circadian rhythms.

What they found

• Bright morning light increases the post-waking cortisol response.
• The human clock resets in response to light timing and intensity, with morning light advancing the rhythm earlier.
• Indoor lighting is usually an order of magnitude too dim to do the job.
• The effect depends on when the light arrives, not just how much of it there is.

What it means for you

An earlier, sharper morning rise means an earlier evening fall — which is what actually produces sleepiness at a sane hour. Women who fix mornings often report the 3 AM wake-up loosening within two weeks without changing anything at night.

What to do with it this week

• Take your coffee outside, or stand at an open door, for 10 minutes.
• On dark mornings, get the light later in the morning rather than skipping it.
• Pair it with something you already do — the dog, the mail, a phone call.
• Sunglasses off for those ten minutes; the signal goes through your eyes.