Seasonal affective disorder (also called 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, sapping your energy and making you feel moody. Less often, seasonal affective disorder causes depression in the spring or early summer.
Treatment for seasonal affective disorder includes light therapy (phototherapy), psychotherapy and medications. Don't brush off that yearly feeling as simply a case of the "winter blues" or a seasonal funk that you have to tough out on your own. Take steps to keep your mood and motivation steady throughout the year.
To learn more: Seasonal Affective Disorder - Mayo Clinic