Seasonal Affective Disorder is a mood disorder subset in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year, most commonly in winter. Common symptoms include sleeping too much, having little to no energy, and overeating. The condition in the summer can include heightened anxiety. Circadian Clock-Related Polymorphisms in Seasonal Affective Disorder and their Relevance to Diurnal Preference