As Daylight Savings Time has kicked in once again this year, now is an important time to discuss the phenomenon known as Seasonal Affective Disorder (SAD). With fewer hours of daylight and more time spent in darkness, combined with colder temperatures and less outdoor time, the human body and mind can be quite affected. This time of year is certainly an adjustment for all, but for some individuals, the fall and winter season can have a big impact.

SAD is currently listed as a type of Major Depressive Disorder, the diagnosis for those experiencing clinically significant depressive symptoms that cause impairment in their daily lives. It is believed that depressive symptoms arise for those with SAD due to the decreased exposure to sunlight. This is thought to be because sunlight boosts serotonin levels, which is believed to play a role in happiness, and conversely – sadness and depression. When longer days and increased sunlight exposure roll around again in spring and summer, the depressive feelings subside. Depressive disorders that do not fit this pattern (absence of symptoms during summer months, or certain months of the year) would not be considered SAD. Additionally, seasonal depressive symptoms that are related to certain events (i.e., school schedule, holidays, seasonal unemployment) are not considered to be SAD.

The symptoms of SAD can include loss of energy, increased need for sleep, increased appetite and/or weight gain, with some researchers believing cognitive functioning is also impacted. They may also include other symptoms commonly seen with depression, including sadness or negative mood, loss of interest in previously enjoyed activities, and hopelessness. SAD affects up to 5% of the U.S. population, including 10% of people living in the Northern U.S. The disorder tends to affect women more than men, which is also true of depression in general. Symptoms of SAD often first appear during one’s 20s and 30s, and younger people tend to be more affected.

While SAD tends to occur most often during the fall and winter months, it is possible for an individual to experience seasonally-based depressive symptoms during the summer months only. The symptoms tend to be the opposite during summer, in which insomnia, low appetite, weight loss, and increased energy/agitation may be present.