The Truth About Seasonal Affective Disorder

Nassir Ghaemi, MD, MPH

February 03, 2011

The Saddest Time of Year

December 21 was the winter solstice: the shortest, hence darkest, day of the year. January 17 (some claim) is the "saddest day of the year," factoring in bad weather, postholiday withdrawal, and the usual effect of return-to-work Mondays on our moods. I believe that this belief is false. Winter is not the saddest time of the year; in fact, springtime is much worse.

Seasonal Affective Disorder vs Depression

Many see seasonal affective disorder (SAD) as synonymous with winter depression. However, depression is only half of the problem; spring and summer mania tend to be ignored. Beginning with winter depression, core symptoms resemble hibernation. People sleep more, eat more, and are less interested in usual activities. They are not sad in mood, typically, and may be unaware that their slowed down, uninterested behavior reflects a kind of depression.

A number of misconceptions are harbored about winter depression. The most frequent, perhaps, is that it has to do with coldness of temperature. Winter depression is not about shivering and freezing. These do not cause depression; decreased light does. It doesn't matter whether it's 70°F or 20°F outside; if there are 10 hours of light in a day rather than 14, then seasonal depression will follow. When I worked in Atlanta, Georgia, many people who used to live in Florida came to me with SAD. Georgia had notably less light than Florida, even though temperatures were only slightly colder.

Moreover, light itself is not the only cause of depression. Light interacts with a person's own sensitivity to depression. Some people, especially those with bipolar disorder or recurrent unipolar depression, are sensitive to changes in light, and will develop winter depression even in areas with reasonable light levels, such as Georgia or Italy. Others are insensitive to light, and will not develop SAD even in areas with low light levels, such as New England or Scandinavia.