Seasonal depression, also known as Seasonal Affective Disorder (SAD), can take a serious toll. Even in otherwise healthy individuals, the onset of winter can bring about severe changes in mood and personal satisfaction. Luckily, a few easy treatments have been shown to minimize the effects of seasonal depression, and to make life more bearable until springtime.

In order to diagnose seasonal depression, the American Psychiatric Association requires that certain criteria be met. Most importantly, SAD demands that depressive episodes begin and end at a certain time of the year (hence, it is seasonal), and patients should display a pattern of this depression over the course of the last two years. In addition, the occurrences of seasonal depression in a person's lifetime should outnumber the number of non-seasonal depressions.

The effects of seasonal depression are little different from classic non-seasonal depression, although symptoms can vary by season. While winter depression may result in oversleeping, depression, weight gain, and social withdrawal, summer depression may incur insomnia, anxiety, weight loss, and even an increased sex drive. Occasionally, these effects can be so severe as to require hospitalization. Rarely, individuals may experience what is known as Reverse Seasonal Affective Disorder. Reverse SAD can result in a minor form of mania, known as hypomania, whose symptoms include hyperactivity and disproportional enthusiasm.

Populations that enjoy significantly less sunlight in winter months (northern countries, or anywhere with heavy cloud cover) have been found to exhibit a increased amount of seasonal depression. Finns, for example, have been diagnosed with SAD at a rate of 9.5%. In the United States, the occurrence of seasonal depression is lowest in Florida, and rises steadily as one moves north. Individuals from Iceland, however (even Canadians with Icelandic ancestors), tend to have markedly lower occurrence of seasonal depression than other Scandinavian people. Scientists suspect this may be due to genetics, or even a fish-heavy diet.

The effects of seasonal depression can be reduced through a few simple acts. Exercise and outdoor activity, on sunny days especially, can prove beneficial. But indoors, light boxes have been credited with producing marked improvements in mood. Since light boxes produce white, full spectrum light similar to natural sunlight, individuals who sit in front of these lamps for 30 to 60 minutes at a time have reported a reduction in their symptoms. These natural remedies are sometimes supplemented with SSRI antidepressant medications, or melatonin.

Some psychologists suspect that seasonal depression stems from an out-of-sync body clock. Advocates of this theory created "dawn simulation," in which the amount of light in the room steadily increases over the course of 30 to 120 minutes. This method of light therapy may provide more flexibility, compared to sitting in front of a light box sometime in the course of a day.