Seasonal affective disorder (SAD) is a type of major depression that cycles with the seasons. It increases in intensity from fall through winter, then lessens in severity (or goes away entirely) during spring and summer.

Symptoms of Seasonal Affective Disorder

Because SAD is a type of major depression, its symptoms are similar. The person with SAD loses interest in their everyday activities. They feel “down” most of the time. They might sleep too much or not enough — oversleeping is more typical for winter SAD. It’s common to experience feelings of guilt, worthlessness, frustration, and fatigue. In some cases, people with seasonal affective disorder contemplate suicide or self-harm.

What Causes Seasonal Affective Disorder?

Researchers don’t know the exact cause of SAD, but they do have theories based on years of studying the disorder. In some cases, those with seasonal affective disorder can’t properly regulate serotonin. They have higher levels of serotonin transporter protein during winter months, making less serotonin available for mood regulation. Researchers have also linked a lack of vitamin D with depression. During winter months, the days are shorter, and the sunlight isn’t typically as strong. This makes it more difficult for the body to synthesize vitamin D.

The shorter days may also throw off a person’s natural circadian rhythms and melatonin levels.

Treatment for Seasonal Affective Disorder

Three main treatment options exist for SAD: medication, light therapy, and counseling. Light therapy uses a special device called a light-box, which emits light that’s about 20 times stronger than ordinary indoor lamps. Using a light-box on a daily basis helps to replace the lack of sunshine associated with fall and winter. A doctor can determine how long and when to use the light-box for optimal results. In general, people with SAD use them from half an hour to as much as two hours a day.

Antidepressants might be necessary in some cases. Doctors often prescribe SSRIs — selective serotonin reuptake inhibitors. Buproprion, a norepinephrine-dopamine reuptake inhibitor (NDRI), is sometimes prescribed, particularly in patients with bipolar disorder.

Counseling, especially cognitive behavior therapy, can be helpful for SAD. This type of therapy focuses on identifying negative behaviors and thoughts and replacing them with more positive, helpful ones.