The terms winter depression or seasonal affective disorder (SAD) describe a form of depression that occurs in the winter months. The prominent symptoms are low mood and lack of energy usually accompanied by excessive sleeping and overeating. Opinion is divided as to whether this is a separate disease from other forms of depression.

These include:

• low mood that starts in autumn or winter
• lack of energy and lethargy
• increased appetite and weight gain (there is often a craving for carbohydrate food)
• increased sleep and daytime sleepiness.