SAD Causes and Risk Factors
Seasonal affective disorder (SAD) is a mood disorder that occurs with changes in the seasons, most commonly during the winter months. Symptoms often involve feeling depressed, sleeping too much, having little energy and craving sweet or starchy foods.
The specific causes of SAD are unknown, though researchers believe that genetics, age and the natural chemical makeup of a person’s body may all play a role in developing seasonal affective disorder. Although winter SAD is most common, seasonal affective disorder can also occur as a result of heat and humidity during the summer months.
Biochemical Imbalance and SAD
Although what causes SAD is unclear, researchers have linked SAD to a biochemical imbalance in the brain triggered by shorter daylight hours and a lack of sunlight in winter. Possible biological changes that may cause SAD include:
- Disruption of a person’s biological clock: Reduced sunlight may disrupt the body’s internal clock (circadian rhythm) that tells you when to sleep or be awake. Cortisol levels, which play a role in stress responses, fluctuate with disruption of the biological clock.
- Melatonin levels: The change in seasons can cause an imbalance in the body’s levels of melatonin, a natural hormone that plays a role in sleep patterns and mood. The body produces melatonin when it’s dark, and increased melatonin levels have been linked to depression.
- Serotonin levels: Less sunlight exposure can cause a drop in serotonin levels, a brain chemical (neurotransmitter) that affects mood.
Research has shown that bright light affects brain chemistry, although exactly how is not yet known. Light therapy — exposure to lights about 20 times brighter than a standard light bulb — is therefore a common treatment to help relieve the symptoms of SAD.
Risk Factors for Seasonal Affective Disorder
Some people are more likely to develop seasonal affective disorder, including women, people who live far from the equator and people with a family history of SAD.
SAD may begin at any age, but must often starts between ages 18 and 30. Also, according to researchers at Penn State, college freshmen with a history of problematic seasonal changes are at a higher risk for developing SAD.
Summer SAD
The causes of SAD in the summer are even less well understood than those of wintertime SAD, but may include high heat and humidity. Only about 1 percent of Americans experience summer SAD.
Resources
American Psychiatric Association Staff. (n.d.). Seasonal affective disorder. Retrieved May 5, 2010, from the American Psychiatric Association website: healthyminds.org/Main-Topic/Seasonal-Affective-Disorder.aspx.
Mayo Clinic Staff. (2009). Seasonal affective disorder. Retrieved May 5, 2010, from the Mayo Clinic website: www.mayoclinic.com/health/seasonal-affective-disorder/DS00195/METHOD=print.
Penn State Erie The Behrend College Staff. (n.d.). Has winter white turned you blue? Retrieved May 5, 2010, from the Penn State Erie website: www.pserie.psu.edu/student/counseling/SAD.htm.