Got the winter blues? Maybe you're SAD. That's Seasonal Affective Disorder. S.A.D. is a type of depression that affects some people every winter between September and April, especially between December and February. It was first described in the 6th century by a scholar, Jordanes, to describe the people of Scandinavia (modern day Norway, Sweden, Finland and Denmark). In the USA the diagnosis of seasonal affective disorder was first proposed by Dr. Norman Rosenthal in 1984; he referred to it as "an energy crisis". He wondered why he became depressed during the winter after moving from sunny South Africa to New York. He started experimenting increasing exposure to artificial light, and found this made a difference.

Some people have the depression in winter accompanied by abnormally increased mood and activity (mania) for periods in the spring or autumn. As many as 20% of sufferers may go on to develop bipolar or manic-depressive disorder.

S.A.D. is thought to be due to altered melatonin metabolism that results from decreased daylight in the winter months. Melatonin is a chemical produced by the pineal gland in the brain, which regulates sleep-wake cycles, sometimes called "circadian rhythm". The pineal gland has connections to the retina in the back of your eyes, and may respond to light. Melatonin is released in the dark, during sleep. Besides S.A.D., melatonin is also implicated in jet lag. Mice incapable of making melatonin show depression-like behaviour. On the other hand, some mice with enhanced melatonin receptors on their brain cells respond as they would to anti-depressants.

Besides depressed mood and apathy, people with this condition have increased sleep accompanied by daytime drowsiness, anxiety, social withdrawal, and irritability Patients also describe increased craving for and intake of carbohydrates as well as weight gain. They can also experience slowing of thought and movement. This slowing is called "psychomotor retardation". Some sufferers may have increased infections in the winter due to weakened immune system response. A diagnosis can be made after the seasonal pattern of these symptoms occurs for 2 years. Prolonged periods of cloudy weather can worsen symptoms. Decreased temperature is not a cause of S.A.D.

S.A.D. can occur at any age but often first strikes between the ages of 18 and 30. People who live in the Arctic are especially susceptible because of the long "polar nights". It is quite rare in people who live within 30 degrees of the equator, where daylight hours are consistently long.

For mild decreased mood in the winter, or "winter blues" as it is sometimes called, the best option is outdoor exercise, particularly on sunny days.

The best treatment for full-on S.A.D. is light (phototherapy). Patients need to get a specially designed light box that is 10 times as intense as normal indoor lighting, and sit in front of it for 2-4 hours a day. If this seems bright, you may be surprised to learn that a bright summer day is 200 times as bright as indoor lights! The light should be used every day in winter starting in early autumn. Sometimes light therapy can be used in combination with antidepressant medication, counseling, or psychotherapy.


Jordanes, Getica, ed. Mommsen, Mon. Germanae historica, V, Berlin, 1882. Uz et al, J Pineal Res 2001 Apr, 30 (3): 166-70 Sumaya et al, J Pineal Res 2005 Sep, 39(2): 170-7 Diagnostic and statistical manual of mental disorders. 4th ed. Washington, D.C.: American Psychiatric Association, 1994:390 Rosenthal, Norman Winter Blues: Everything You Need to Know to Beat Seasonal Affective Disorder.Revised edition ,Guilford Press; New York, 2005.

Dr. Hasini Reddy is a Rhodes Scholar whose PhD research focused on brain imaging techniques (University of Oxford, England). She completed her medical degree at Memorial University (St. John’s, ND), and is now a medical resident at the University of Western Ontario specializing in neurology and pathology. She enjoys reading, traveling and horseback riding.


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