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What is it?

Light therapy is a treatment used for people who suffer from circadian rhythm sleep disorders. Your body has an internal clock that tells it when it is time to be asleep and when it is time to be awake.

This clock is located in the brain just above an area where the nerves travel to the eyes. This area is called the SCN. Your clock controls the “circadian rhythms” in your body. These rhythms include body temperature, alertness and the daily cycle of many hormones.

The word “circadian” means to occur in a cycle of about 24 hours. Circadian rhythms make you feel sleepy or alert at regular times every day. Some people have a circadian rhythm sleep disorder. This causes their natural sleep time to overlap with regular awake activities such as work or school.

Among other factors, your clock is “set” by your exposure to bright light such as sunlight. Exposure to bright light or “light therapy” is one method used to treat people with a circadian rhythm sleep disorder.

The goal for treating patients who have circadian rhythm problems is to combine a healthy sleep pattern with an internal clock that is set at the right time. This will allow them to enjoy the benefits of good sleep.

Light therapy can help someone “re-set” a clock that is off. Regular sleep patterns help to keep the clock set at the new time. Light therapy is only part of a treatment plan that should be guided by a doctor who is familiar with sleep disorders.

Light therapy is used to expose your eyes to intense but safe amounts of light for a specific and regular length of time. In many places, sunlight is not available at the proper time to be used as treatment.

Artificial light may be used to affect the body clock in the same way that sunlight does. New advances continue to be made in this field. Currently, products that are used for light therapy fit into four basic groups:

1. Light Box

This is the most common tool that is used in light therapy. The box houses several tubes that produce extremely bright light. It sits on top of a table or desk and plugs into the wall.

During a treatment session, you have to keep within a certain distance of the box. Usually, you will be about 18 to 24 inches away from it. It does not require you to look directly into the light. Instead, you simply face in the direction of the box.

You are able to do other activities during the session. Ideally, you would work on papers or read something that is in the area being lit up. This will allow the light to be received by your eyes. Your body takes in this information and uses it to regulate the rhythms that control when you sleep and when you wake.

Earlier models of light boxes put out 2,500 to 5,000 lux of light. Lux is a measure of how much light falls on your eyes. These sessions could take two or three hours. Now, many boxes produce 10,000 lux of light. This allows sessions to take as little as 15 to 30 minutes.

More than one session may be needed each day. It depends upon your body, your need, and the strength of light being used. The key is to use the light at the right time of day and for the right amount of time. This is based upon the sleep disorder you want to correct.

New models are also safer, protecting you from harmful UV rays. Some models are now focusing on a specific bandwidth of light. Light boxes can be purchased in a variety of makes and models. Some are now being made much smaller so they are easier to take with you. General prices range from $200 - $500 per light box.

2. Desk Lamp

This serves the same purpose as a light box, but it is made to look like a normal lamp. It blends in better when used in an office setting.

3. Light Visor

This is a light source that is worn on your head and hangs over your eyes. It looks much like a tennis visor. It is made so that you can move around during sessions. The strength of visor lights also varies from 3,000 to 10,000 lux.

4. Dawn Simulator

These lights gradually make a dark room brighter over a set period of time. This is meant to mimic the sunrise. Some people may find that this helps them wake up in the morning. Models may also slowly dim to copy a sunset.

Who gets it?

Bright light therapy is used for people who suffer from circadian rhythm disorders. The time of day when the light is used will depend upon the disorder it is meant to correct. These disorders include the following:

1. Delayed sleep phase disorder

This causes people to fall asleep much later at night than is normal. As a result, they also wake up later in the morning. This sleep pattern can interfere with their schedule of activities for the day. To correct delayed sleep phase, light treatment takes place during the early morning hours.

2. Advanced sleep phase disorder

This causes people to fall asleep much earlier at night than is normal. They also wake up earlier in the morning. To correct it, light treatment takes place early at night.

3. Free-running or Non-24-hour sleep-wake rhythm

People with this disorder fall asleep at a different time each day. For example, you may fall asleep at 10 p.m. one day, Midnight the next day, 2 a.m. the next, etc. This most often occurs in people who are blind. Light therapy may help blind people, even if they can't perceive visible light. Studies show that light treatment may be useful in the early morning hours.

4. Jet lag

Jet lag causes people to have problems with sleep when they have crossed many time zones on a flight. Light therapy in the morning may help when traveling east. For travel to the west, bright light in the evening may help reduce jet lag.

5. Shift Work

This sleep disorder occurs due to a work schedule, such as night shift, that takes place during the time when most people are sleeping. This schedule requires you to work when your body wants to sleep. Then you have to try to sleep when your body expects to be awake. Correcting it can be a hard problem to solve. Changing work schedules, days off, and social activities can alter your exposure to light from day to day. Frequent changes in your sleep times make it hard to re-set your internal clock. In general, using light treatment in the evening should help someone who regularly works nights. In this case, you would also want to avoid daylight when you come off work and go to bed. Dark sunglasses or special goggles can help.

6. Seasonal affective disorder (SAD)

SAD is a mood disorder that can cause people to feel sad and lack energy during the dark months of winter. A similar and milder version is often called the “Winter Blues.” In severe forms, sadness may be caused by depression. Light therapy is thought to be useful as one of the treatments for seasonal mood disorders and depression. Depression is also treated with medications. You should consult your doctor if you are having serious problems with sadness.

Possible side effects?

Light therapy has a good record of safety. It does not seem to produce any major side effects. Light therapy should always be used within the proper limits for intensity and time. Minor side effects may include the following:

• Eye irritation and dryness
• Headache
• Nausea
• Dryness of skin

To reduce these side effects, begin the light therapy very slowly. Give your body time to get used to it. The use of a humidifier can also help with irritations caused by dryness. Talk to your doctor or a sleep specialist before beginning use.

Reviewed by Norman J. Wilder, MD
Updated on May 11, 2006