How common is seasonal affective disorder?
Research indicates that the occurrence of winter-type SAD may vary depending on the latitude at which a person lives, as well as sex and age. Specifically, the disorder is more common in higher latitudes—it is 7 times more common in Washington state than in Florida, and in Alaska, the prevalence rate is 8.9 percent, and higher for subsyndromal SAD, at 24.9 percent. It is also higher for women and among people in their 20s. Generally, estimates of the prevalence of the disorder range from 4 to 6 people out of 100, while 10 percent to 20 percent of the population may have milder forms of SAD. Some studies indicate that it usually doesn’t start in people younger than age 20, however, one study found up to a 5 percent occurrence rate for children in Minnesota (albeit with fewer children experiencing a full depressive episode).
