What is Seasonal Affective Disorder?
Seasonal affective disorder* is a form of depression also known as SAD, seasonal depression or winter depression. People with SAD experience mood changes and symptoms similar to depression. The symptoms usually occur during the fall and winter months when there is less sunlight and usually improve with the arrival of spring. The most difficult months for people with SAD in the U.S. tend to be January and February. While it is much less common, some people experience SAD in the summer.
SAD is more than just “winter blues.” The symptoms can be distressing and overwhelming and can interfere with daily functioning. However, it can be treated. About 5 percent of adults in the U.S. experience SAD and it typically lasts about 40 percent of the year. It is more common among women than men.
SAD has been linked to a biochemical imbalance in the brain prompted by shorter daylight hours and less sunlight in winter. As seasons change, people experience a shift in their biological internal clock or circadian rhythm that can cause them to be out of step with their daily schedule. SAD is more common in people living far from the equator where there are fewer daylight hours in the winter.