Seasonal affective disorder

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Seasonal affective disorder
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Haleigh Williams, B.S.

Synonyms and keywords: SAD; seasonal disorder; seasonal depression; winter blues; winter depression

Overview

Seasonal affective disorder (SAD), also known as winter depression, is a form of depression that is correlated with changes in the season. In the most common form of SAD, an individual experiences more frequent depressive periods between the late fall and early spring, with no such instances in the late spring and summer months. Less commonly, patients may experience depressive episodes in the summer; this type of disorder is often referred to as reverse seasonal affective disorder.

Historical Perspective

SAD was first described during the 1980s by South African physician Normal Rosenthal, who noticed that he felt significantly less industrious and energetic during the winters following his move to the United States, though he returned to his normal state during the spring.

Classification

Rather than being defined as its own distinct disorder, SAD is classified as a specific type of depression that involves a persistent association between depressive episodes and seasonal changes.

Pathophysiology

Though the physiological basis of SAD is not completely clear, people with SAD seem to suffer from some of the following hormonal/neurotransmitter imbalances more frequently than the general population:

• Serotonin. Studies have shown that individuals suffering from winter-occurring SAD produce more serotonin transporter protein in the winter months than in the summer months, which means serotonin has less of an effect.
• Melatonin. In the winter, as days become shorter and periods of darkness lengthen the production of melatonin increases. This can interfere with a patient’s circadian rhythm and induce lethargy and drowsiness.
• Vitamin D. Patients with SAD tend to produce less vitamin D than their unaffected counterparts; this deficiency may play a role in exacerbating depression through interference in the action of serotonin.

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright light therapy. SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N), where the rate of SAD is 9.5%. Cloud cover may contribute to the negative effects of SAD.

SAD can be a serious disorder and may require hospitalization. There is also potential risk of suicide in some patients experiencing SAD. One study reports 6-35% of sufferers required hospitalization during one period of illness. The symptoms of SAD mimic those of dysthymia or clinical depression. At times, patients may not feel depressed, but rather lack energy to perform everyday activities. Norman Rosenthal, a pioneer in SAD research, has estimated that the prevalence of SAD in the adult United States population is between about 1.5 percent (in Florida) and about 9 percent (in the northern US).

Various etiologies have been suggested. One possibility is that SAD is related to a lack of serotonin, and serotonin polymorphisms could play a role in SAD, although this has been disputed. Another theory is that melatonin produced in the pineal gland is the primary cause since there are direct connections between the retina and the pineal gland. Mice incapable of synthesizing melatonin appear to express "depression-like" behaviors, melatonin receptor ligands produce an antidepressant-like effect Subsyndromal Seasonal Affective Disorder is a milder form of SAD experienced by an estimated 14.3% vs. 6.4% of the U.S. population. The blue feeling experienced by both SAD and SSAD sufferers can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure. Connections between human mood, as well as energy levels, and the seasons are well-documented, even in healthy individuals. Particularly in high latitudes (50°N or S) it is common for people to experience lower energy levels.

Treatment

There are several different treatments for seasonal affective disorder, including light therapies, medication, and ionized-air reception. Bright light treatments are common, though as many as 19% of patients discontinue use because of the inconvenience. Specially designed light, many times brighter than normal office lighting, is placed near the sufferer, and has proven to be effective at doses of 2,500-10,000 lux. Most treatments use 30-60 minute treatments, however this varies depending on the situation. The sufferer sits a prescribed distance, generally between 30 and 60 cm, in front of the box with her/his eyes open but not staring at the light source. Many patients prefer to use the light box in the morning, though it has not been proven any more effective then as compared to any other time of day. Discovering the best schedule is essential because up to 69% of patients find it inconvenient. Dawn simulation has also proven to be more effective in some studies, there is an 83% better response when compared to bright light. When compared in a study to negative air ionization however, bright light was proven to be 57.1% effective vs. dawn simulation, 49.5%. Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks. Most studies found it effective without use year round, but rather as a seasonal treatment lasting for several weeks until frequent light exposure is naturally obtained. SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Bupropion is also effective as a prophylactic. Effective antidepressants are fluoxetine, sertraline, or paroxetine. Both fluoxetine and light therapy are 67% effective in treating SAD according to direct head-to-head trials. Negative air ionization, involving the release of charged particles into the sleep environment, has also been found effective with a 47.9% improvement. Depending upon the patient, one treatment (e.g., lightbox) may be used in conjunction with another therapy (e.g., medication).

Throughout the world

Scandinavia

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 genetically heritable. It was first described by the 6th century Goth scholar Jordanes in his Getica where he described the inhabitants of Scandza (Scandinavia). There are words in Icelandic and Swedish that directly describe seasonal affective conditions. The Icelandic word is "skammdegisthunglyndi." "Skamm" means short, "degi" is day, "thung" is heavy and "lyndi" means mood, although there is some argument as to how long the word existed as the earliest records indicate it appeared in the late 1800s in print.

United States

In the United States, a diagnosis of seasonal affective disorder was first proposed by Norman E. Rosenthal, MD in 1984. Rosenthal wondered why he became muggish 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. In Alaska it has been established that there is an SAD rate of 8.9%, and an even greater rate of 24.9% for subsyndromal SAD.

SAD and bipolar disorder

Most people with SAD experience unipolar depression, but as many as 20% may have or go on to develop a bipolar or manic-depressive disorder. In these cases, people with SAD may experience depression during the winter and hypomania in the summer.

See also

• Depression (mood)
• Circadian rhythm sleep disorder

References

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