Seasonal Affective Disorder (SAD) is a type of depression that occurs at the same time every year. If you’re like most people with seasonal affective disorder, your symptoms start in the fall and may continue into the winter months. Most severe are December, January & February, sapping your energy and making you feel moody.
SAD can affect people of any age, including children. Sunlight can affect some of the brain’s chemicals and hormones. One theory is that light stimulates part of the brain called the hypothalamus which controls mood, appetite and sleep. These things can affect how you feel. The lack of light is thought to affect: The production of the hormone melatonin. The production of the hormone serotonin. The body’s circadian rhythm (the body’s internal clock, which regulates several biological processes during a 24-hour period).