What is seasonal affective disorder?

Seasonal affective disorder, or SAD, is a type of depression that occurs in the fall and winter months, when exposure to daytime sunlight is diminished. The lack of natural sunlight may lead to severe symptoms of depression in some people. The symptoms generally go away when spring arrives and do not return until the following fall/winter.

Symptoms of SAD are similar to those of any type of depression, with the addition of some specific somatic (physical) symptoms. They include the following:

Fatigue;
Lack of interest in activities a person once enjoyed;
Withdrawal from social interactions;
Difficulty focusing;
Irritability;
Weight gain;
Craving for foods high in carbohydrates;
Insomnia or oversleeping.

People with SAD may not have all of the symptoms listed above, or some may be severe, whereas others are mild. In rare instances, some people experience SAD during the summer season, due possibly to uncomfortable heat and humidity. In these patients, the SAD involves symptoms such as insomnia, reduced appetite, weight loss and irritability/anxiety.
The more common version of SAD, which occurs in the winter, is thought to be related to a biochemical brain imbalance caused by fewer hours of daylight and sun. The restricted hours of sunlight may induce a change in the body’s circadian rhythms, or biological clocks. Research has shown that the farther a person lives from the equator, the more likely they are to experience SAD.

SAD also is thought to be connected to the sleep-related hormone melatonin. Melatonin, which is generated by darkness, helps trigger sleep. In the winter, when daylight is in shorter supply, melatonin production increases and can lead to depression.

Bright light therapy (phototherapy) through a fluorescent lamp or “light box” is one known treatment for SAD. Although it is not known precisely how this treatment works, researchers have determined that between 30 and 90 minutes of daily exposure to this light may positively affect brain chemistry. Long walks outside or sun exposure through a window also may be useful.

In more severe cases of SAD, light therapy alone may not be enough. For these patients, psychotherapy or an antidepressant medication (or both) may be valuable in getting through the winter months.

Additional information may be found at these websites:

http://www.psychiatry.org/mental-health/seasonal-affective-disorder

http://www.nlm.nih.gov/medlineplus/seasonalaffectivedisorder.html