Seasonal affective disorder

Seasonal affective disorder (SAD), also known as winter depression, 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 or summer. The condition in the summer is often referred to as Reverse Seasonal Affective Disorder.

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Pathophysiology

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright light therapy.^[1] SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N) where the rate of SAD is 9.5%^[2] Cloud cover may contribute to the negative effects of SAD.^[3]

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.^[3] 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.^[1] 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.^[3]

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,^[4] although this has been disputed.^[5] Another theory is that the cause may be related to melatonin which is produced in dim light and darkness by the pineal gland, 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.^[6]

Subsyndromal Seasonal Affective Disorder is a milder form of SAD experienced by an estimated 14.3% vs. 6.4% of the U.S. population.^[7] 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.^[8] Connections between human mood, as well as energy levels, and the seasons are well-documented, even in healthy individuals.

Treatment

  There are many different treatments for seasonal affective disorder, including light therapies, medication, and ionized-air reception. Bright light treatments are common, however as many as 19% of patients stop use because of the inconvenience.^[2] A specially designed lamp, many times brighter than normal indoor lighting, is placed near the sufferer, and has proven to be effective at doses of 2500 - 10,000 lux.^[7] Most treatments use 30-60 minute treatments, however this varies depending on the situation. The sufferer sits a prescribed distance, commonly 30-60 cm, in front of the box with her/his eyes open but not staring at the light source.^[2] Many patients use the light box in the morning, however it has not been proven any more effective than any other time of day.^[7] Discovering the best schedule is essential because up to 69% of patients find it inconvenient.^[2] Dawn simulation has also proven to be more effective in some studies, there is an 83% better response when compared to other bright light therapy.^[2] When compared in a study to negative air ionization however, bright light was proven to be 57.1% effective vs. dawn simulation, 49.5%.^[9] Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks.^[2] 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.^[1] SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Bupropion is also effective as a prophylactic.^[3] Effective antidepressants are fluoxetine, sertraline, or paroxetine.^[1][10] Both fluoxetine and light therapy are 67% effective in treating SAD according to direct head-to-head trials.^[1] Negative air ionization, involving the release of charged particles into the sleep environment, has also been found effective with a 47.9% improvement.^[9] Depending upon the patient, one treatment (ie. lightbox) may be used in conjunction with another therapy (ie. medication).^[1]

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 Scandinavians are affected, and it seems to be genetically heritable.^{[citation needed]} It was first described by the 6th century Goth scholar Jordanes in his Getica wherein he described the inhabitants of Scandza (Scandinavia).^[11]

Iceland

A study of more than 2000 people in Iceland found the prevalence of seasonal affective disorder and seasonal changes in anxiety and depression to be unexpectedly low in both sexes.^[12] The study's authors suggested that propensity for SAD may differ due to some genetic factor within the Icelandic population. A study of Canadians of wholly Icelandic descent also showed low levels of SAD.^[13]

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 sluggish 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 a SAD rate of 8.9%, and an even greater rate of 24.9%^[14] for subsyndromal SAD.

Ireland

Around one in five Irish people are affected by SAD, according to a survey conducted in 2007. The survey also shows women are more likely to be affected by SAD than men. ^[15]

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.^[16] In these cases, persons with SAD may experience depression during the winter and hypomania in the summer.

Famous sufferers

• Natalie Imbruglia, a famous Australian singer, suffered from SAD during a longer stay in London, England.^[17]
• Science fiction-fantasy author Barbara Hambly suffered with undiagnosed SAD for many years.^[18]

See also

• Depression (mood)
• Circadian rhythm sleep disorder
• Wilson's Thyroid Syndrome

References