It’s possible that you may be suffering from seasonal affective disorder or SAD.
As we switch seasons into fall and winter, the days get shorter, nights longer and a lack of sunlight goes along with it. This can trigger a certain type of depression known as seasonal affective disorder or SAD. People who are affected by SAD may begin to experience depression, sadness and fatigue. This symptoms begin to fade away in spring, as the days get longer and increase in sunlight.

Studies show that women tend to develop this disorder more than men but children can also show signs of seasonal affective disorder as well. To read more from Harvard Medical School about seasonal affective disorder, symptoms and how to treat it, click here and here.