The holidays are over and everyone seems a little down. Is it the holiday blues or something more serious? According to Dr. Norman Rosenthal, a noted researcher in the field, six percent of the U.S. population, primarily in northern climates, is affected by the most extreme symptoms of Seasonal Affective Disorder or SAD. Another 14 percent of the adult U.S. population suffers from "winter blues" a milder form of the disorder.As the days become longer - particularly after daylight savings time when it gets dark earlier - people with SAD start to slow down and have a hard time waking …