Seasonal Affective Disorder (SAD)

SAD is a disorder where depressed feelings will change in response to the season.  The amount of sunlight the person experiences during different periods has a great affect on their mood.  The most common time of year for a person to experience this depression is in the Winter time. 

According to the Diagnostic and Statistical Manual of Mental Disorders, the criteria for SAD are that:

1. The person experiences a regular pattern of depressive episodes, which begin at a certain time of the year.
2. The depressed mood also stops or changes at a regular time each year.
3. It has lasted longer than 2 years.
4. The person has experienced more seasonal types of depression than other types (Major depression for example).

Sometimes people experience the reverse of this effect, having a depressive episode during Summer and starting to feel better towards Winter.  This is known as Summer SAD, and is quiet rare.

In some extreme cases of SAD the sufferer may also experience significant social withdrawal. Eventually, with the onset of spring the sufferer comes out of 'hibernation' and depending on circumstances improvement is almost immediate.  The emotional difficulties that occur with depression also occur with SAD, however instead of insomnia and lack of eating, people with SAD tend to sleep more and eat greater amounts of sweets and carbohydrates  than normal during their depression period. 

In some people the effect of SAD can be quite severe and bring about symptoms of depression that interfere with normal daily functioning.  The good news is that it is usually treated with 'Bright Light Therapy' which has minimal side-effects.  Sunlight entering through the retina stimulates the production of chemicals in the brain and appears to have an antidepressant effect.

People who live at higher latitudes tend to have less sunlight, and therefore experience higher rates of SAD. Australia receives a good amount of sunlight due to its position on the globe, and as such, SAD is rare in this country.   SAD is also more prevalent in people who are younger, and typically affects more women than men.

References:

Pathophysiology of seasonal affective disorder: A review
Journal of Psychiatry and Neuroscience, 25, 469-480
Raymond W. Lam and Robert D. Levitan
2000

The diagnosis, symptomatology, and epidemiology of seasonal affective disorder
CNS Spectrums, 10, 625-634
Andres Magnusson and Timo Partonen
2005

Light therapy for seasonal and nonseasonal depression: Efficacy, protocol, safety, and side effects
CNS Spectrums, 10, 647-663
Michael Terman and Jiuan Su-Terman
2005