Light, Screens, and the Body Clock

Use light strategically without making screens the only explanation for poor sleep.

Light is a timing signal

The circadian system responds to light. Light exposure after waking helps communicate that the day has begun. Bright light late in the evening can make it harder for some people to feel sleepy at the intended time. Timing, intensity, and duration all matter.

Screens are one part of the picture

Phones and televisions expose the eyes to light, but their effect is not limited to the screen itself. Engaging content, stressful messages, games, and scrolling can delay bedtime. A screen used for calm audio at low brightness may have a different effect from an activity that keeps the mind alert.

Create a transition into night

Try brighter natural light earlier in the day and a calmer, dimmer environment as bedtime approaches. Set a realistic stopping point for stimulating activities. People with unusual work schedules or suspected circadian rhythm disorders may need individualized guidance.