Why is bright light at night bad for sleep?

Bright light at night is detrimental to sleep because it can shift our circadian rhythm and suppress the release of melatonin, the hormone that promotes sleepiness 1. Exposure to light late at night can make it harder for us to wake up early and go to bed early due to the phase delay it causes, which tells our bodies to get up and go to sleep later than we should 2.

Additionally, artificial bright light between 10 PM and 4 AM has been found to negatively impact the dopamine circuits in the brain, which can lead to lower mood and affect learning 3. Andrew Huberman advises avoiding bright light at night and dimming any artificial lights we use during this time to promote better sleep quality and mood regulation.