|Seasonal affective disorder (SAD) can develop from inadequate bright light during the winter months. Researchers have discovered that bright lights change the chemicals in the brain, and that there is a biochemical imbalance in the hypothalamus due to the shortening of daylight hours. Details of its effects are being studied. It has been found that low levels of Vitamin D in the blood can attribute to this and other depressive disorders.
Some people experience a serious mood change when the seasons change. They may sleep too much, have little energy, and crave sweets and starchy foods. Between 4% and 6% of people in the United States suffer from SAD. Another 10% to 20% may experience a mild form of winter-onset SAD.
Exposure to light may help if it is of sufficient brightness, approximately 25 times as bright as normal room light. This phototherapy does not have to be actual daylight from the sun. What is most important is the quantity, not necessarily the quality of light in the therapy of seasonal affective disorder.
Antidepressant medications, particularly serotonin selective reuptake inhibitor (SSRI) family, have been found to be an effective treatment for seasonal affective disorder. Examples of SSRIs include Prozac, Aoloft, Paxil and Celexa.