Introduction

Key points

Bright light therapy is an effective treatment for seasonal affective disorder (SAD). 1, 2
Light therapy is easy and safe. It has few side effects and can be done at home.
People who have eye problems or take medications that cause sensitivity to light should not use light therapy without first consulting a health professional.
What is light therapy?
Why is light therapy used to treat SAD?
How is light therapy done?

What is light therapy?

Light therapy is treatment with a special type of light that is much brighter than a lamp or other light fixture in your home. The most common form of this therapy is done with a light box that contains fluorescent—not ultraviolet or full-spectrum— lights.

To use light therapy, you sit at a prescribed distance from the light box. The amount of exposure you need depends on the intensity of light you use and could range anywhere from 15 minutes to 2 hours. The intensity of light usually ranges between 2,500 and 10,000 lux (10,000 lux is about 20 times as bright as normal indoor lighting).

Although light boxes are the most common type of light therapy, dawn simulation is also used. With dawn simulation, a low-intensity light gradually comes on while you're sleeping, about 2 hours before you usually wake up. Some studies suggest that dawn simulation may not be as effective as light box therapy. 1

Test Your Knowledge

The amount of time you need to sit in front of a light box depends on how strong of a light you use.
True
The answer is correct

The amount of exposure you need depends on the intensity of light you use and could range anywhere from 15 minutes to 2 hours.

False
The answer is incorrect

The amount of exposure you need depends on the intensity of light you use and could range anywhere from 15 minutes to 2 hours.

Why is light therapy used to treat SAD?

Most people with seasonal affective disorder become depressed in the fall and winter, when days are shorter and sunlight is limited. Although researchers are still studying the exact cause of SAD, some believe the body's 24-hour biological clock (circadian rhythms), which controls sleep/wake cycles, may be affected by seasonal changes of light and darkness and that subsequent biochemical changes in the brain may cause depression. Light therapy helps to "reset" your biological clock.

Light therapy, which has few side effects, is also an alternative to taking medications to treat depression. It can also be used with medications and counseling.

Test Your Knowledge

Light therapy is used to offset changes in the body's 24-hour clock that may cause depression.
True
The answer is correct

Seasonal cycles of light and darkness may trigger changes in the body's 24-hour clock and lead to depression.

False
The answer is incorrect

Seasonal cycles of light and darkness may trigger changes in the body's 24-hour clock and lead to depression.

How is light therapy done?

Most light therapy is prescribed at 10,000 lux for about 30 to 60 minutes in the early morning. Studies vary as to whether light therapy at other times of the day is less effective, but some people with SAD (perhaps those who wake up normally in the early morning) should do their light therapy for 1 to 2 hours in the evening, ending 1 hour before bedtime.

Most research shows that light box therapy is more effective than dawn simulation. However, some people who find it inconvenient to use a light box may want to try dawn simulation.

Once you begin light therapy, your initial response will determine whether you need the intensity or duration adjusted. Many people respond to light therapy within 3 to 5 days, but they may relapse back into depression if they miss treatment for 3 days in a row during winter. 1 If you don't respond to treatment within the first week, you may notice improvement in the second week.

The most common side effects of light therapy include headache, eye strain, and nausea. You may be tired during the first week because of changes in your sleep/wake patterns, but this will usually go away after about a week.

Light therapy is usually started in the fall and continued through spring.

Your health professional can help you decide which light exposure schedule will work best for you. Most lights used in light therapy can be found on the Internet. Beware of manufacturers that market inexpensive light therapy devices that have not been researched for effectiveness or documented for safety. The safest light is fluorescent, not full-spectrum or ultraviolet light.

If you have any eye problems, talk with your ophthalmologist before beginning light therapy. Make sure your health professional knows all of the medications you are taking as well.

Test Your Knowledge

Answer the following question.

I should receive 10,000 lux of light therapy each morning for about 30 to 60 minutes every day.
True
The answer is correct

Your health professional will help you determine the most effective amount of time you need to be exposed to light therapy daily. You may want to start with 60 minutes of light therapy daily and adjust the time based on your initial reaction and reduction of symptoms. You should not use a lamp that puts out more than 10,000 lux of light at a distance of 12 to 18 inches.

False
The answer is incorrect

Your health professional will help you determine the most effective amount of time you need to be exposed to light therapy daily. You may want to start with 60 minutes of light therapy daily and adjust the time based on your initial reaction and reduction of symptoms. You should not use a lamp that puts out more than 10,000 lux of light at a distance of 12 to 18 inches.

Talk with your health professional

Take this information with you and work with your health professional to create a treatment plan that works for you.

Related Information

Depression
Melatonin
Seasonal Affective Disorder (SAD)