Technically speaking, Season Affective Disorder is not a separate diagnosis but is actually one of the sub-types of Major Depressive Disorder. But, for practical purposes, it can be useful to think about Seasonal Affective Disorder as an actual diagnosis. As the name implies, Season Affective Disorder is a mood disorder that goes along with the seasons. Often it's considered and associated with winter blues and the idea is that people get depressed when the days get shorter. But, actually, it can be any season and some patients have symptoms in the summer or in the spring and the key factor with the Seasonal Affective Disorder is that it happens every year around the same time time of year, and manifests with the same symptoms. Usually symptoms that look just like a depressive episode, but again, they're triggered specifically by the changing of the season. We know that they have something to do with the length of the days because the incidents of Seasonal Affective Disorder is more common in places like New Hampshire where they have longer winters and shorter summers and the incidents are lower in places like Florida where they have longer summers and shorter winters. Seasonal Affective Disorder can be treated just like major depression and once it's diagnosed, it's useful because the treatment can be started in anticipation of when the symptoms are going to come. So, for example, if you tend to have winter blues, treatment can be started in the Fall and treatment can consist of medications but also light therapy can be very useful to manage Seasonal Affective Disorder. And that's a basic introduction on Seasonal Affective Disorder.