Seasonal Affective Disorder (SAD) is a mood disorder felt by many in the winter. It is characterized by a seasonal depression, 'the blues', a desire to oversleep or withdraw, and often a craving for starchier foods. While the 'winter blues' have long been recognized, Seasonal Affective Disorder has only been studied since the 1980s. Its mechanism is still not understood, but intuitively, it seems to be an evolutionary holdover from a more close-to-nature past. When the days grow short and the nights are long, our ancestors might have expected to curtail their activities, retreat to a cozy shelter and sleep a good portion of the time, spending their waking hours perhaps effecting repairs to their hunting equipment and telling stories around a communal fire pit.
Since our modern lifestyle doesn't make room for the need to hibernate like this, people can find themselves dealing with the stress of being forced into day-to-day activities when they only want to tell stories and sleep. Thus, Seasonal Affective Disorder is a very real physiological phenomenon, and one that can be treated. It is thought that shorter days and lack of daylight may cause overproduction of melatonin, a hormone related to sleep that is created in the pineal gland; overproduction of melatonin is often followed by depression. Current treatment for Seasonal Affective Disorder uses full-spectrum lights for a few hours -- even as little as an hour -- a day, which suppress the secretion of melatonin and thus elevate the SAD-sufferer's mood.
If you typically go through a period of depression in the wintertime, particularly in January and February, which lack holidays to lift the mood, and you do not suffer depression any other time of the year, chances are good that you are affected by Seasonal Affective Disorder. Some studies claim that as many as ten to thirty percent of adults in countries with significant season changes are affected by Seasonal Affective Disorder to some degree. Most Seasonal Affective Disorder sufferers may find that simply walking out of doors for an hour a day gives them sufficient daylight to reduce symptoms. Others may need to try indoor light therapy, or even medication. It is perhaps unfortunate that we can no longer simply retreat to the cave for some quality oversleeping and starch snacking.
