Everyone may find themselves with a bit of a blue mood every now and then during the long stretches of winter, but seasonal affective disorder, or SAD, is more than just a day or two of the blues. It is a major depressive disorder that strikes certain people typically during certain parts of the year. In the United States, it is most common in the northernmost states, occurring 4 to 5 times more often there than in the southernmost states. (Source: Sarason and Sarason 2005) For the diagnosis of SAD, which is technically called “recurrent mood disorder with seasonal pattern” in the DSM-IV-TR, the diagnostic tool for psychologists, the depressive mood has to occur at a particular time of the year, go completely away or have a complete change in mood pattern at another time of the year and recur in subsequent years for at least two years.