Seasonal Affective Disorder (SAD), also known as winter depression or winter blues, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or, less frequently, in the summer, spring or autumn, repeatedly, year after year. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), SAD is not a unique mood disorder, but is "a specifier of major depression".
The US National Library of Medicine notes that "some people experience a serious mood change when the seasons change. They may sleep too much, have little energy, and crave sweets and starchy foods. They may also feel depressed. Though symptoms can be severe, they usually clear up." The condition in the summer is often referred to as Reverse Seasonal Affective Disorder, and can also include heightened anxiety. It has been estimated that 1.5-9% of adults in the US experience SAD.
There are many different treatments for classic (winter-based) seasonal affective disorder, including light therapy with sunlight or bright lights, antidepressant medication, cognitive-behavioral therapy, ionized-air administration, and carefully timed supplementation of the hormone melatonin.
Symptoms
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Symptoms of SAD may consist of: difficulty waking up in the morning, tendency to oversleep as well as to overeat, and especially a craving for carbohydrates, which leads to weight gain. Other symptoms include a lack of energy, difficulty concentrating on completing tasks, and withdrawal from friends, family, and social activities. All of this leads to the depression, pessimism, and lack of pleasure which characterize a person suffering from this disorder.
People that experience Reverse SAD (spring and summer depression) show symptoms of insomnia, anxiety, irritability, decreased appetite, weight loss, and an increased sex drive. RSAD can also manifest depression, which makes it difficult to diagnose this rare affliction.
Diagnostic criteria
According to the American Psychiatric Association DSM-IV, criteria, Seasonal Affective disorder is not regarded as a separate disorder, but is called a 'course specifier' and may be applied as an added description to the pattern of Major Depressive Episodes in patients with Major Depressive Disorder or patients with Bipolar Disorder. The Seasonal Pattern Specifier must meet four criteria: depressive episodes at a particular time of the year; remissions or mania/hypomania also at a characteristic time of year; these patterns must have lasted two years with no nonseasonal major depressive episodes during that same period; and these seasonal depressive episodes outnumber other depressive episodes throughout the patient's lifetime. The Mayo Clinic describes three types of Seasonal Affective Disorder, each with its own set of symptoms.
Physiology
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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 (64ยบ 00´N) where the rate of SAD is 9.5% Cloud cover may contribute to the negative effects of SAD.
The symptoms of SAD mimic those of dysthymia or clinical depression. 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. At times, patients may not feel depressed, but rather lack energy to perform everyday activities.
Various proximate causes have been proposed. 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. Mice incapable of turning serotonin into N-acetylserotonin (by Serotonin N-acetyltransferase) appear to express "depression-like" behavior, and antidepressants such as fluoxetine increase the amount of the enzyme Serotonin N-acetyltransferase, resulting in an antidepressant-like effect. 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, via the retinohypothalamic tract and the suprachiasmatic nucleus, between the retina and the pineal gland.
Subsyndromal Seasonal Affective Disorder is a milder form of SAD experienced by an estimated 14.3% vs. 6.1% of the U.S. population.[14] 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.
Mutation of a gene expressing melanopsin has been implicated in the risk of having Seasonal Affective Disorder.
Origin
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In many species, activity is diminished during the winter months in response to the reduction in available food and the difficulties of surviving in cold weather. Hibernation is an extreme example, but even species that do not hibernate often exhibit changes in behavior during the winter. It has been argued that SAD is an evolved adaptation in humans that is a variant or remnant of a hibernation response in some remote ancestor. Presumably, food was scarce during most of human prehistory, and a tendency toward low mood during the winter months would have been adaptive by reducing the need for calorie intake. The preponderance of women with SAD suggests that the response may also somehow regulate reproduction.
If these interpretations are correct, SAD would not be a dysfunction or disorder as most psychiatrists assume, but rather a normal and expected response to seasonal changes.
Treatment
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There are many different treatments for classic (winter-based) seasonal affective disorder, including bright light therapy, medication, ionized-air administration, cognitive-behavioral therapy and carefully timed supplementation of the hormone melatonin.
Photoperiod-related alterations of the duration of melatonin secretion may affect the seasonal mood cycles of SAD. This suggests that light therapy may be an effective treatment for SAD. Bright light therapy often includes the use of a lightbox which emits far more lumens than a customary incandescent lamp. White light, or "full spectrum" light is usually preferred, although blue light is also used.
Lightbox therapy is effective at doses of 2500–10,000 lux, with the patient sitting a prescribed distance, commonly 30–60 cm, in front of the box with her/his eyes open but not staring at the light source. Most treatments use 30–60 minute treatments, however this may vary depending on the situation. Many patients use the light box in the morning, and there is evidence that morning light is superior to evening light, although people can respond to evening light as well. Discovering the best schedule is essential. One study has shown that up to 69% of patients find the treatment inconvenient and as many as 19% stop use because of this.
Dawn simulation has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy. When compared in a study to negative air ionization, 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 have found it effective without use year round, but rather as a seasonal treatment lasting for several weeks until frequent light exposure is naturally obtained.
Light therapy can also consist of exposure to sunlight, either in the form of spending more time outside , or using a computer-controlled mirror device called a heliostat to reflect sunlight into the windows of a home or office.
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 conducted during the 2006 CAN-SAD study. Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment.
Negative air ionization, which involves releasing charged particles into the sleep environment, has also been found effective with a 47.9% improvement if the negative ions are in sufficient density (quantity). Depending upon the patient, one treatment (ie. lightbox) may be used in conjunction with another therapy (ie. medication).
Modafinil may be also an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.
Alfred J. Lewy of Oregon Health and Science University in Portland, OHSU, and others see the cause of SAD as a misalignment of the sleep-wake phase contra the period of the body clock, circadian rhythms out of synch, and treat it with melatonin in the afternoon. Correctly timed melatonin administration shifts the rhythms of several hormones en bloc.
Another explanation is that vitamin D levels are too low when people do not get enough Ultraviolet-B on their skin. An alternative to using bright lights is to take vitamin D supplements. However, one study did not show a link between vitamin D levels and depressive symptoms in elderly Chinese.
Incidence
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Nordic countries
Winter depression is a common slump in the mood of some inhabitants of most of the Nordic countries. It was first described by the 6th century Goth scholar Jordanes in his Getica wherein he described the inhabitants of Scandza (Scandinavia). Iceland, however, seems to be an exception. A study of more than 2000 people there found the prevalence of seasonal affective disorder and seasonal changes in anxiety and depression to be unexpectedly low in both sexes. 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. It has more recently been suggested that this may be attributed to the large amount of fish traditionally eaten by Icelandic people, 225 lb per person per year as opposed to about 50 lb in the US and Canada, rather than to genetics. Fish is high in vitamin D. Fish also contains docosahexaenoic acid (DHA), which has been shown to help with a variety of neurological dysfunction.
Other countries
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% for subsyndromal SAD.
Around 20% of 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. An estimated 10% of the population in the Netherlands suffers from SAD.
SAD and bipolar
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Most people with SAD experience major depressive disorder, but as many as 20% may have or may go on to develop a bipolar disorder, a manic-depressive disorder. It is important to discriminate the improved mood associated with recovery from the winter depression and a manic episode because there are important treatment differences. In these cases, persons with SAD may experience depression during the winter and hypomania in the summer.
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