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Seasonal Affective Disorder (SAD) - Treatment, Symptoms, Cause and Light Therapy of Seasonal Affective Disorder


Seasonal Affective Disorder form of depression always occurs during the winter months, which is why it is termed seasonal affective disorder. It is thought to occur because the daylight hours are so short in our winter.

Seasonal Affective Disorder affects about half a million Britons quite severely and others have it to a lesser degree. In the summer a lot of light enters the eye and then travels to the brain. Here it probably acts in two ways: it reduces the production of melatonin, which causes sleepiness and apathy; it also increases the production of serotonin, the feel-good chemical (low levels of serotonin are thought to be the basis of depression).

Therefore when there is little daylight in the winter we have more melatonin, making us sleepy and also increasing apathy, and lower levels of serotonin, making depression more likely.

People who become depressed and apathetic in the winter often benefit from extra light exposure. Ideally this would mean migrating to a sunny climate, but a special light box may completely prevent the symptoms of depression.

Disclaimer: This site is for educational purposes only. The information provided should not be used for diagnosing or treating a health problem or disease. If you have, or suspect you have a health problem, you should consult your health care provider.