Winter brings with its darker mornings and evenings, and some may feel they hardly see the sunlight at all---going to work in the dark and coming back home in the dark. Many people find themselves feeling sad, blue and even depressed around the winter. The medical name for winter depression is seasonal affective disorder (SAD). It’s fairly common, and it’s more mild than serious. You wake up before the sun even rises, you might start feeling a persistent low mood or lack of energy. The cause of SAD is not fully understood, shorter days seem to be a main trigger for it. Reduced sunlight in winter can disrupt your body’s internal clock, or circadian rhythm. This 24-hour clock responds to cues in your surroundings, especially light and darkness. At night, the brain produces melatonin, helping you sleep. Light stops the brain producing melatonin to help keep you awake. Shortened daylight in winter may increase the production of melatonin and affect the body’s internal clock or circadian rh