Evening exposure to blue light suppresses melatonin release through sustained elevation of cortisol levels, leading to impaired sleep onset and maintenance.

Study: Home lighting, blue-light filtering, and their effects on melatonin suppression

The study shows that bright, blue-like evening lights (like from cool LEDs) reduce the sleep hormone melatonin more than warmer, dimmer lights. This supports the idea that blue light at night can mess with sleep.

Study: Managing Blue Light Exposure: Impacts on Sleep Quality and Circadian Health

The study shows that too much blue light at night can make it harder to fall asleep by reducing a sleep hormone called melatonin. This supports the main idea in the claim, though it doesn’t mention the stress hormone cortisol.

Study: Effect of evening blue light blocking glasses on subjective and objective sleep in healthy adults: A randomized control trial.

The study looked at whether blue light blocking glasses help people sleep better, but found little real improvement in sleep, even though people felt slightly better. It didn’t check the hormones involved, so it doesn’t prove the idea that blue light messes with sleep through cortisol and melatonin.

Study: Effect of daylight LED on visual comfort, melatonin, mood, waking performance and sleep

The study looked at blue-enriched light during the day and found it didn’t lower melatonin levels or hurt sleep — in fact, people felt more alert and slept more deeply. This goes against the idea that blue light in the evening messes up sleep by affecting melatonin and cortisol.