Winter brings seasonal affective disorder

Less sunshine in the winter can trigger symptoms of seasonal affective disorder, which strikes between 4% and 6% of the U.S. population and is more common in women in their 20s to 40s. Genetics may play a role in SAD, and for some, light therapy, psychotherapy or medication can help reduce symptoms.

http://www.cnn.com/2008/HEALTH/conditions/11/14/seasonal.affective.disorder/index.html