Seasonal Affective Disorder

For winter SAD, the most effective treatment is bright light therapy.

Verla Chatsis, BScPharm, Drug Information Pharmacist, Regional Drug Information Centre, University of Alberta Hospital

Seasonal affective disorder is a form of depression that is associated with a particular season. In northern countries like Canada, the depression generally starts in the fall or winter, and ends in spring or summer. Signs and symptoms of SAD include a lack of energy, sadness, anxiety, irritability, a lowered sex drive, overeating, weight gain, and cravings for sugars and starchy foods. People with SAD are relatively inactive and withdraw from normal social activities. They have trouble sleeping, which makes them want to sleep longer.

To be diagnosed with SAD, a person must be depressed during a specific season over at least two years. The depression is not considered to be SAD if it caused by sources of stress which occur at the same time annually such as seasonal unemployment or going back to school. SAD mostly affects adults and usually starts from ages 20 to 30. Men are more likely to experience a more severe form of SAD than women.

The cause(s) of SAD are not fully understood. Shorter days associated with winter may trigger SAD by disturbing normal body rhythms. Changes in rhythm affect the levels of substances in the body like melatonin and serotonin, which may cause the depression.

For winter SAD, the most effective treatment is bright light therapy. The light must have a brightness of at least 2500 lux (the average home is around 100 lux). Patients receive light treatment for 1 – 2 hours daily. Patients usually start to improve after one to two weeks of treatment. If the light therapy works, the treatment is continued throughout the winter season at least 5 times per week. Although most people tolerate light therapy well, they may have some side effects like eyestrain, headache, and hypomania (persistent elevated mood, hyperactivity, inflated self esteem).

Antidepressant medications may be used in patients that don’t respond to light therapy. These drugs are helpful in those who are severely depressed. Other treatments including negative ion treatments, dawn therapy (which mimics dawn by raising light levels in the morning), and aerobic exercise with sleep deprivation have been tried in SAD but they are not as effective as light therapy.