Bright Light Therapy

What is bright light therapy?

Bright light therapy is a treatment for circadian rhythm sleep disorders — conditions where your internal body clock is out of sync with when you need to be awake or asleep.

Your body clock sits in a region of the brain called the suprachiasmatic nucleus (SCN), located just above where the optic nerves meet. It controls your circadian rhythms: body temperature, alertness, and the daily cycle of hormones that regulate when you feel sleepy or awake.

One of the primary signals that sets this clock is exposure to bright light. Light therapy works by exposing your eyes to intense but safe amounts of light at specific times, effectively nudging the clock earlier or later depending on your disorder. In many climates and seasons, natural sunlight isn't available at the right time — artificial light therapy replicates the same effect.

What are the types of bright light therapy?

Light box

This is the most common tool for light therapy. The box houses several tubes that produce extremely bright light and sits on a table or desk. During a session, you stay within 18 to 24 inches of the box — you don't need to look directly into it, just face toward it. You can read, work, or use a computer during the session. Newer models produce 10,000 lux, reducing session time to as little as 15 to 30 minutes. They also filter out harmful UV rays.

Desk lamp

This serves the same purpose as a light box but is designed to look like a normal lamp. It blends in more naturally in an office or home setting.

Light visor

A wearable light source that hangs over the eyes like a tennis visor. It allows you to move around freely during sessions. Light strength varies from 3,000 to 10,000 lux.

Dawn simulator

These lights gradually brighten a dark room over a set period of time, mimicking a natural sunrise. Some people find this helps them wake up more easily. Many models also slowly dim to simulate a sunset.

What disorders does it treat?

Delayed sleep-wake phase disorder — you fall asleep much later than normal and wake up late. Use bright light therapy soon after waking up.

Advanced sleep-wake phase disorder — you fall asleep very early and wake before dawn, sometimes as early as 3:00 or 4:00 a.m. Use bright light therapy in the early evening.

Free-running sleep-wake rhythm disorder — sleep onset shifts later each day. Most common in people who are blind. Light therapy in the early morning may help.

Jet lag — morning light therapy helps when traveling east; evening light therapy helps when traveling west.

Shift work disorder — if you work nights, evening bright light therapy can help align your body clock with your schedule. Avoiding daylight after your shift ends (dark sunglasses can help) reinforces the effect.

What are the possible side effects?

Light therapy has a strong safety record. Minor side effects may include eye irritation or dryness, headache, nausea, or dry skin. Start slowly to give your body time to adjust, and use a humidifier if dryness is an issue. Always consult a sleep doctor before beginning light therapy.