During the winter months, the days get shorter and the nights longer. For many people–an estimated 6 to 10 percent of Americans–this change of schedule triggers a type of depression called seasonal affective disorder [SAD]. Symptoms can appear gradually or come on all at once, beginning in late fall then subsiding in spring–and often returning year after year.
SAD has been linked to biochemical changes in the brain that occur when daylight hours become shorter. Reduced sunlight affects the body’s internal circadian rhythms or biological clock–which tell the body when to sleep or awaken. When there is a lack of sunlight, the body takes it as a signal to increase the production of melatonin, a sleep-related hormone that has been linked to depression. Increased darkness also appears to affect the body’s production of serotonin, a neurotransmitter that affects mood. Low levels of serotonin have been linked to depression.
Symptoms of SAD include eating more than is usual; gaining weight; having difficulty staying awake; sleeping excessively; experiencing a drop in energy; being unable to maintain your regular lifestyle and schedule; having feelings of sadness, hopelessness, depression and irritability; losing interest in social interactions; and suffering a decreased sex drive and lack of enjoyment. Not everyone who has SAD experiences the same symptoms. Symptoms can range from mild to severe. Remission of symptoms usually occurs during the spring and summer months.
Light therapy is the most common treatment for SAD. Light therapy includes exposure to a broad-spectrum light for a minimum of 20 to 30 minutes per day. The light intensity should be at least 10,000 lux. Treatment may also include melatonin supplements, antidepressant medications and psychotherapy.
If you think you or someone you love may be affected by SAD, contact your physician to confirm that you are experiencing SAD. It is better not to diagnose yourself, because your symptoms may be associated with another medical condition, like thyroid disease, hypoglycemia, infectious mononucleosis or other viral infections. SAD can also be confused with major depression and bipolar disorder. Getting treatment that is right for you can help you function better and make a big difference in your life.