Can bright bedroom lights at night trigger early puberty in children?

What's actually in it

Modern bedrooms are rarely truly dark. Night lights, device screens, standby LEDs, and light leaking from hallways and streetlamps all contribute to the amount of light hitting a child's eyes during sleep. This artificial light at night (ALAN) suppresses melatonin, the hormone that regulates sleep and also helps control the timing of puberty.

Puberty is starting earlier in children worldwide, and researchers have been looking for environmental causes beyond diet and body weight.

What the research says

A 2026 longitudinal study in JAMA Netw Open followed children over two years and measured bedroom light levels along with puberty markers. Children who slept in brighter bedrooms entered puberty earlier than those in darker rooms.

The connection runs through melatonin. Light at night suppresses melatonin production in the pineal gland. Since melatonin normally puts a brake on the hormones that trigger puberty (like gonadotropin-releasing hormone), less melatonin means that brake is released too soon.

The study measured light with sensors placed in children's bedrooms, so it captured actual light exposure, not just screen time. Even low-level ambient light, like a nightlight or open door with hall light on, made a measurable difference.

Early puberty is linked to higher risks of depression, early sexual behavior, and certain cancers in adulthood. Make your child's bedroom as dark as possible with blackout curtains, remove or cover device LEDs, and keep nightlights as dim as possible. Red or amber light disrupts melatonin less than blue or white light.