A street lamp outside your window, the orange charging light on a plug adapter next to your nightstand, a flash of your phone late at night indicating you’ve received an email—these artificial light sources would never occur in nature, and recent studies suggest they harm your brain.

Higher levels of artificial light at night were linked to increased stress-related activity in the brain, inflamed arteries, and a higher risk of heart disease, according to a preliminary study presented at the American Heart Association’s Scientific Sessions 2025.

Artificial light at night, or nighttime light pollution, is a nearly universal feature of modern cities, according to the study. This first-of-its-kind study reviewed brain scans and satellite images to show a biological pathway linking nighttime

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