In the spring and summer, when you wake up with the sun and go to bed when it's dark, your body's internal clock is in synch with the sun. However, in the winter, when most people must force themselves to wake up while it's still dark, the sleep-wake circadian rhythm is thrown off-kilter from all of the body's other rhythms. For nearly 25 million Americans, this internal imbalance means their autumn and winter months are spent suffering from the many symptoms of Seasonal Affective Disorder (SAD), including depression, low energy, chronic anxiety, weight gain, social withdrawal, and an increased need for sleep.

If you are diagnosed with SAD, your doctor or therapist may suggest you try light therapy to treat your symptoms. Light therapy involves daily exposure to high-intensity, artificial sunlight (full-spectrum light minus the ultraviolet) delivered by either a specially made desk-type light box or a light visor that you wear on your head like a cap. Light treatment usually begins with a single 10 to 15 minute session per day, gradually increasing the duration to 30 or 45 minutes. In some cases, the light therapy sessions are increased to twice a day if the symptoms continue to persist or worsen.

If your therapist or physician prescribes light therapy, you should be prepared to maintain your light treatment sessions daily from October through April, since the symptoms of SAD will recur quickly and abruptly if light therapy is discontinued before the onset of Spring brings more available natural light. Although some people experience almost immediate relief from light therapy, it usually takes two to four days to experience a sustained antidepressant response.

It's important to note that tanning beds should not be used to treat SAD. The light sources for tanning beds are high in ultraviolet (UV) rays and can be very harmful to the eyes, cause sunburn, and significantly increase the risk for skin cancer.

When properly administered, light therapy appears to have few side-effects--and none that are irreversible. Even so, there are some potential side-effects you should be aware of:

• Eye strain



• Photophobia (sensitivity to or intolerance of light)



• Headache



• Fatigue



• Irritability



• Inability to sleep (especially when light therapy is used too late in the day)

Because light boxes can be purchased without a doctor's prescription, many mental health experts are extremely worried that people will erroneously self-diagnose themselves with SAD and that light boxes will then be tried by those who are actually suffering from a serious mental disorder that will then go untreated and become even worse. If you or someone you know thinks they may be suffering from SAD, it's very important to seek a professional diagnosis from either a doctor or therapist.

Although light therapy can be a uniquely effective type of treatment for SAD, treatment plans should always include consideration of all the treatment options, including therapy (behavioral therapy is especially helpful), medication (antidepressants or monoamine oxidase inhibitors) or a combination of therapy, light, and medication.