The human circadian rhythm system is genetically designed to respond to morning light. People who don't get enough morning light, like overnight shift workers, airplane pilots, people with seasonal affective disorder (SAD) and certain sleep problems, can experience troubling symptoms like weight gain, fatigue and depression. Light therapy can help.
Light and Melatonin
Morning light controls the body's melatonin production, which affects the body's circadian rhythm or sleep/wake cycle.
Symptoms of Seasonal Affective Disorder (SAD)
Twenty-five percent of people living at 38 degrees north latitude and higher, which includes the northernmost parts of California, Nevada, Utah, Colorado, Kansas, Missouri, Illinois, Indiana, Kentucky, West Virginia, Virginia and Maryland (and all U.S. states north of them), have symptoms in fall and winter related to the later sunrise. Symptoms can include weight gain, fatigue, intense carbohydrate craving, difficulty waking on time and depression. These symptoms are collectively known as seasonal affective disorder or SAD.
Light Treatment Retrains the Brain
SAD light treatment early in the morning provides the signal the circadian system is seeking. It alters the body's secretion of melatonin. The result is a more normal sleep-wake cycle and abatement of symptoms.
Light Treatment is Effective
In 2005 an American Psychiatric Association work group agreed that light is a first-line treatment of choice for both seasonal and nonseasonal depression. Fifty to 80 percent of people with SAD get relief treatment.
Light Treatment Scenarios
Shift workers and those with jet lag from light therapy. It trains your brain and internal clock to get in sync with local time. People who fall asleep and wake too early or too late can also benefit.
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