What are symptoms of seasonal affective disorder (SAD)?

According to MayoClinic.com, symptoms of winter-onset SAD include feeling depressed and/or hopeless, lacking energy, feeling anxious,  finding it hard to concentrate, feeling like it takes too much effort to socialize or do things you usually enjoy, sleeping more than usual, craving simple carbohydrates (like sweets and fast foods), eating too much and gaining weight.    More information can be found at http://www.mayoclinic.com/health/seasonal-affective-disorder/DS00195/DSECTION=symptoms   

Tomorrow we look at what causes SAD.