Seasonal affective disorder (SAD) is a type of depression that typically occurs each year during fall and winter. Use of a light box can offer relief. But for some people, light therapy may be more effective when combined with another SAD treatment, such as an antidepressant or psychotherapy, also called talk therapy.

Light boxes are designed to deliver a therapeutic dose of bright light to treat symptoms of SAD. There are many different types of light boxes. All light boxes for SAD treatment are designed do the same thing, but one may work better for you than another.

It's best to talk with your health care provider about choosing and using a light box. If you're experiencing both SAD and bipolar disorder, the advisability and timing of using a light box should be carefully reviewed with your health care provider. Increasing exposure too fast or using the light box for too long each time may induce manic symptoms if you have bipolar disorder.

If you have past or current eye problems such as glaucoma, cataracts or eye damage from diabetes, get advice from your eye specialist before starting light therapy.

A light therapy box mimics outdoor light. It's thought that this type of light may cause a chemical change in the brain that lifts your mood and eases other symptoms of SAD, such as being tired most of the time and sleeping too much.

Generally, the light box should:

• Provide an exposure to 10,000 lux of light
• Produce as little UV light as possible

Typical recommendations include using the light box:

• Within the first hour of waking up in the morning
• For about 20 to 30 minutes
• About 16 to 24 inches (41 to 61 centimeters) from your face, but follow the manufacturer's instructions about distance
• With eyes open, but not looking directly at the light

Light boxes aren't regulated by the Food and Drug Administration (FDA) for SAD treatment, so it's important to understand your options.

You can buy a light box without a prescription, but it's best to use it under the guidance of a health care provider and follow the manufacturer's guidelines. Your health care provider may recommend a specific light box. Most health insurance plans don't cover the cost.

Here are some questions to think about when buying a light box for seasonal affective disorder:

• Is it made specifically to treat SAD? If not, it may not help your depression. Some light therapy lamps are designed for skin disorders — not for SAD. Lamps used for skin disorders mainly produce ultraviolet (UV) light and could damage your eyes if used incorrectly.
• How bright is it? Light boxes produce different intensities of light. Brighter boxes will require less time to use each day, compared with dimmer boxes, to achieve the same effect. Usually, the recommended intensity of light is 10,000 lux.
• How much UV light does it release? Light boxes for SAD should be designed to filter out most or all UV light. Contact the manufacturer for safety information if you have questions.
• Can it cause eye damage? Some light boxes include features designed to protect the eyes. Make sure the light box filters out most or all UV light to avoid damaging your eyes. Ask your eye specialist for advice on choosing a light box if you have eye problems such as glaucoma, cataracts or eye damage from diabetes.
• Is it the style you need? Light boxes come in different shapes and sizes, with varied features. Some look like upright lamps, while others are small and rectangular. Smaller light boxes are more portable and easier to pack if you're traveling during fall and winter. The effectiveness of a light box depends on daily use, so buy one that's convenient for you.
• Can you put it in the right location? Think about where you'll want to place your light box and what you might do during its use, such as reading, doing a craft or watching TV. Check the manufacturer's instructions, so you receive the right amount of light at the proper distance.

Talk to your health care provider about light box options and recommendations, so you get one that's best suited to your needs.