Seasonal affective disorder (SAD) affects over 10 million Americans. The effects of SAD can be devastating. It can affect your quality of life, and 6% of sufferers require hospitalization. Another 10 or 20 per cent of Americans may have a mild form of the disease, which affects women four times as often as men. The symptoms are wide-ranging and can include:

• Feelings of hopelessness and sadness
• Oversleeping
• Cravings for sweet and starchy foods
• Weight gain
• Heaviness in the arms or legs
• Reduced energy
• Difficulty concentrating and irritability
• Suicidal thoughts

There is no known cause, but SAD, sometimes known as winter depression, may be linked to a lack of sunlight. Because of this, light therapy is often offered as a treatment, either as an alternative to other treatments or in combination with other treatments. Here is what you need to know about light therapy for seasonal affective disorder.

What is Light Therapy?

Light therapy, also known as phototherapy, helps alleviate SAD symptoms and other conditions through exposure to artificial light. The artificial light is often provided through a device known as a light box, which emits a bright light meant to mimic natural outdoor light.

How it Works

Light therapy can be conducted at home. The patient will sit or work near the light therapy box at a distance of about 16 to 24 inches (41 to 61 centimeters). Your eyes should remain open. Physicians will often restrict patients who are new to this kind of treatment to shorter exposures until it is clear how much light exposure they can tolerate. Initially, this will mean 10 or 20 minutes. Times can be increased to 30 minutes or up to two hours, depending on the intensity of the light box you are using.

For a 10,000-lux ("lux" refers to a measure of light intensity) light box, daily sessions are usually about 20 to 30 minutes, but they may be much longer for a lower intensity box.

The time of day for using the light box also varies with each patient. Light therapy is generally recommended for early morning, but some people who suffer from SAD and awaken early on their own are encouraged to do one to two hours in the early evening instead.

Side Effects and Risks

Light therapy is generally considered safe. Most side effects are mild and do not last long. Eye strain is one possible risk with using light therapy. If you already suffer from eye problems, it is recommended that you speak with your ophthalmologist before proceeding with the treatment.

Other possible side effects can include:

• Headache
• Nausea
• Irritability or agitation

Mania, euphoria, hyperactivity or agitation associated with bipolar disorder are also risks for specific patients.

Light therapy is not something you should try on your own. It's best to be under the care of a physician so that you can avoid any potential issues and side effects. This is especially true if you have a history of skin cancer. Specific conditions and medications may also make you sensitive to light. For example, some antibiotics, anti-inflammatories and St. John's Wort may increase your sensitivity to light.

What to Expect

Your first exposure to light therapy should give you a good idea of what you can tolerate and whether you need to adjust the therapy's intensity or duration. Many people respond within three to five days, although it can take several weeks or months for some individuals to see positive light therapy results.

Ensuring Effectiveness

Light therapy will not cure SAD, but it can alleviate many SAD symptoms, improving your energy and mood. You could start to see an improvement within a few days, but more likely, it will take several months of treatment. You can help ensure effectiveness by being consistent with your routine of light therapy sessions. Try to fit it in every day.

You should also ensure that you keep track of when you're using your light therapy lamp, for various reasons. For example, you may not need light therapy in the summer, but if you track when you stop and when your symptoms begin to return, you can ensure you stop and start at the right times the following year.

Also note that light therapy by itself may not be enough for you. If you need to, include other treatments, but discuss these first with your doctor.

How to Choose a Light Therapy Box

Since light boxes are not regulated by the Food and Drug Administration (FDA), it is important to know what to look for. There are many products on the market that are either ineffective or inappropriate for use in alleviating SAD symptoms. Here are a few things to consider:

• Look for a lamp that filters out UV light and is glare-free or can be positioned to reduce glare.
• Don't get a light box that is designed to treat skin conditions as these are often ineffective with SAD.
• Look for a lamp that generates 10,000 lux of white light. White light is the type that has been studied the most.
• The surface area of the lamp should be twelve to fifteen inches. If it is too small it will not be effective.
• Consider where you will be positioning the lamp and the activity you will be doing while you use it.

Light therapy can be an effective treatment for an illness that affects many in North America. Alone, or in combination with other interventions, it can alleviate many of the more persistent symptoms that are associated with SAD, potentially improving quality of life for millions.