Seasonal affective disorder (SAD), a mood disorder that causes depression during the winter months, occurs much more commonly in some geographic locations than in others.
SAD occurs two to four times as often in women as in men.
People affected by SAD usually begin experiencing symptoms in their 20s. Some people outgrow this condition, while others suffer for life.
Although children and the elderly can experience SAD, it is much less common than in young or middle-aged adults.
Often referred to as “the winter blues” or “winter depression,” SAD seems to be related to a lack of sufficient exposure to daylight and an upset with the body’s internal clock, although the exact cause is currently unknown.
Symptoms of SAD, which usually begin during the month of October and continue until April, include:
- crying spells
- food cravings (especially sweets and starches)
- increase or decrease in appetite
- lack of concentration and focus
- withdrawal from family and friends
- weight gain or loss.
A Matter of Degree
In tropical regions close to the equator, cases of SAD are extremely rare. In fact, almost no one who lives right around the equator (from 0 to 29 degrees north or south of the equator) suffers from seasonal affective disorder.
However, once you travel 30 degrees away from the equator, either to the north or south, you begin to find statistically measurable occurrences of SAD.
Researchers estimate that this condition affects:
- 1 percent of Florida residents
- 4 percent of Washington, D.C., residents
- 9 percent of Alaska residents.
While percentages of SAD increase as you travel further north or south of the equator, once you reach latitudes where SAD is very common, it doesn’t seem to matter how much further from the equator you go.
For example, the rate of SAD in Fairbanks, Alaska, is about 9 percent, which is almost identical to the incidence of SAD in New Hampshire.
Although studies are still being conducted to figure out the exact number of SAD sufferers, researchers estimate that between 2 percent and 6 percent of Americans suffer from moderate to severe SAD.
An additional 10 percent of people in the United States may suffer from a milder form of the winter blues.
SAD and Temperature
While many people may associate SAD with bitter cold winters, temperature doesn’t seem to play a part in the frequency of this condition.
Parts of North America with mild winters, such as Vancouver and Seattle, still have a problem with SAD. This is because their latitudes are high enough that light exposure is decreased during the winter months.
Cloudy Day and Office Blues
In addition to latitude, prolonged overcast skies in any geographic location can increase the problem of SAD.
When the skies are cloudy, our exposure to sunlight is limited. Long periods of dark, cloudy weather may bring on symptoms of SAD or worsen them for people already suffering from this problem.
Many people in geographic locations worldwide think their jobs are making them depressed, but they may actually be suffering from a form of SAD.
In fact, working indoors without nearby windows for an extended period of time can produce year round SAD symptoms due to a lack of exposure to natural light.