What is seasonal affective depressive disorder and why is it more common after we move our clocks forward and back?

Seasonal affective disorder, or SAD, is a form of depression that most often occurs during the fall and winter months when daylight hours are shortened. SAD is not just “winter blues” as symptoms can significantly interfere with daily functioning.

Symptoms of SAD include feeling very tired, sleeping too much, overeating (cravings for carbohydrate rich foods), feeling sad or depressed, lack of interest or pleasure in previously pleasurable activities, low motivation, acting withdrawn, restlessness, concentration problems, indecisiveness, and, if severe, thoughts of death or suicide.

Generally, SAD is more common among women than men and affects approximately 5 percent of adults in the United States. Symptoms usually improve in the early spring and summer months although a small percentage of individuals experience SAD symptoms during the summertime. Not surprisingly, SAD is more common in people who live further from the equator where daylight hours are much shorter during the winter months.

The prevailing hypothesis for why SAD occurs relates to our internal biological clock, also called our circadian rhythm. Our circadian rhythm directs our sleep-wake cycle, our mood, our appetite, our hormone levels, and other important functions. An abrupt change in daylight hours may perturb our rhythm and cause our brains to be “out-of-tune.” In other words, as the duration of daylight hours changes, people can experience a shift in their internal clocks which interferes with daily routines.

How can the effects of seasonal affective depressive disorder be minimized?

Fortunately, there are effective strategies for alleviating symptoms of SAD. The first thing to do is create a routine and stick to it. Behavioral strategies such as daily exercise, healthy well balanced diet rich in Vitamin D, and a consistent sleep routine are helpful for many people. Humans are creatures of habit, so going to sleep and waking up at the same time each day is crucial to maintain the integrity of our circadian cycles. Talk therapy can also be very helpful.

Many people have benefited from happy lamps or happy lights, which are special lamps that mimic natural sunlight. However, it is important to consult with your physician before trying this as it can make some psychiatric disorders worse. Medications are usually a last resort, but the most studied medication for this indication is the noradrenergic-dopamine reuptake inhibitor, bupropion (Wellbutrin).

If we stopped moving our clocks twice each year, might we see fewer cases of seasonal affective depressive disorder?

Although there are no studies that prove a causal link between daylight savings and depression, there are studies that show associations between daylight savings time transitions and increased incidence of depressive episodes. While it makes sense theoretically, more research is needed. Based upon what we know, it is plausible that eliminating daylight savings would result in fewer cases of seasonal affective disorder.