Seasonal affective disorder

From Academic Kids

Seasonal affective disorder, or SAD, is an affective, or mood disorder. Most SAD sufferers experience normal mental health throughout most of the year, but experience depressive symptoms in the winter. SAD is rare, if existent at all, in the tropics, but is measurably present at latitudes of 30°N (or S) and higher.


Cause and treatment

Connections between human mood, as well as energy levels, and the seasons are well-documented, even in normal humans. Particularly in high latitudes (50°N or S) it is common for people to experience lower energy levels during the winter. Colds and flu also peak during this time, and most people get less outdoor exercise than in the summer.

Seasonal mood variations are believed to be related mostly to daylight, not temperature. For this reason, SAD is prevalent even in mid-latitude places with mild winters, such as Seattle. Prolonged periods of overcast weather can also exacerbate SAD. Normal "winter blues" can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure. SAD, however, is a more serious disorder, sometimes triggering dysthymia or clinical depression. It may require hospitalization.

Various etiologies have been suggested.2 One possibility is that SAD is related to a lack of serotonin and that exposure to full-spectrum artificial light may improve the condition by stimulating serotonin production although this has been disputed.3, 4 Another theory is that melatonin produced in the pineal gland is the primary cause.5, 6 There are direct connections between the retina and the pineal gland however some studies show that melatonin levels do not appear to differ between those with and without SAD. Light therapy appears to be effective in treating SAD, but the exact mechanism of the effect is still unknown.

Full-spectrum bulbs and "sunlight lamps" can be purchased as speciality lighting products for those suffering from SAD. The most validated of the light therapies is the use of a bright light box for 30-60 minutes daily in the mornings. These light boxes are many times more bright than regular indoor lighting7.

One recent trial seemed to indicate that shining a bright light behind the sufferers' knees would be beneficial, but when the trial was duplicated on a larger scale, the results were negative.

Medication is a more recent treatment and selective serontonin reuptake inhibitors (SSRI's) have proven effective in treating SAD. Examples of these antidepressants are fluoxetine (Prozac), sertraline (Zoloft), or paroxetine (Paxil)8.

Several controlled studies have shown dawn simulation to be as effective as bright lights in treating SAD, with fewer side effects and greater convenience. A specialized control device called a dawn simulator gradually brightens ordinary bedside lights during the hour before the patient awakens.9


Winter depression (or winter blues) is a common slump in the mood of Scandinavians. Doctors estimate that about 20% of all Swedes are affected, and it seems to be hereditary. It was first described by the 6th century Goth scholar Jordanes in his Getica where he described the inhabitants of Scandza (Scandinavia). In the USA the diagnosis of seasonal affective disorder was first proposed by Norman E. Rosenthal, MD on the basis of a depressive syndrome the native of sunny South Africa experienced during his first winter of his graduate training in New York.


1 Shakespeare, W. Life and death of King Richard III (Act I, Scene i)

2 Seasonal affective disorder: autumn onset, winter gloom - board review (

3 Johansson C, et al, (2001), Seasonal affective disorder and serotonin-related polymorphisms. Neurobiol Dis. 2001 Apr;8(2):351-7. (

4 Johansson C, et al. (2003), The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality. Psychol Med. Jul;33(5):785-92. (

5 The Merck manual (

6 National mental health association article (

7 UBC FAQ for SAD (

8 SAD Information from the WSC Counseling Center (

9 Avery DH et al, (2001) Dawn simulation and bright light in the treatment of SAD: a controlled study. Biol Psychiatry. Aug 1;50(3):205-16.  (

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