Normally, morning light appears to signal the brain to suppress production of melatonin, a hormone which regulates sleep. Light also may regulate production of brain chemicals which control our mood. When hours of darkness are prolonged, we may not get enough light to stimulate these reactions. Many people with SAD respond to bright light therapy. The most common device is a bank of white fluorescent lights with a metal reflector and a plastic screen to diffuse the light.
Most people begin to feel better within two to four days of therapy.
Light therapy should be used under the guidance of a physician because it can have side effects, such as headache, fatigue, irritability, insomnia, and excitability. Patients with certain eye conditions, such as macular degeneration and diabetic retinopathy, should only use light therapy under the guidance of an eye care professional. Researchers have developed a new device for treatment of SAD, called the Derma-Lux light Pad. In the morning, the patient unplugs the pad from the charger, wraps it around the leg behind the knee, and relaxes for about an hour. The device contains a band of diodes which shine light on the skin.