Seasonal affective disorder (SAD) is commonly associated with winter months but some people suffer from the disorder in the summer, reports an article in CNN. People affected by summer SAD tend to lose their appetite and experience insomnia. Summer SAD is less common than the winter version and is often overlooked by researchers who study seasonal affective disorder. Researchers believe that the depression may be caused by the heat or by too much sunlight. Current treatments involve staying inside with the curtains drawn and fans and air-conditioning operating at full blast.