Seasonal affective disorder Classification and external resources
Light therapy lamp for Seasonal Affective Disorder
DiseasesDB	11910
MedlinePlus	001532
MeSH	D016574

Seasonal affective disorder (SAD), also known as winter depression, is a mood disorder whose sufferers experience normal mental health throughout most of the year, but experience depressive symptoms in the winter. As stated by the U.S. National Library of Medicine:

"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."^[1]

Pathophysiology

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright light therapy.^[2] SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N) where the rate of SAD is 9.5%^[3] Cloud cover may contribute to the negative effects of SAD.^[4]

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.^[4] 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.^[2] 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.^[4]

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,^[5] although this has been disputed.^[6] Mice incapable of turning serotonin into N-acetylserotonin (by Serotonin N-acetyltransferase) appear to express "depression-like" behaviors, and antidepressants such as fluoxetine increase the amount of the enzyme Serotonin N-acetyltransferase, resulting in an antidepressant-like effect.^[7] 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.^[8] 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.^[9] Connections between human mood, as well as energy levels, and the seasons are well-documented, even in healthy individuals.

Symptoms

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According to the Mayo Clinic^[10] there are three types of Seasonal Affective Disorder, each with its own unique set of symptoms. The three types of SAD are:

Fall and winter SAD (winter depression)
Symptoms of winter-onset seasonal affective disorder include:

1. Fatigue
2. Depression
3. Hopelessness
4. Anxiety
5. Loss of energy
6. Social withdrawal
7. Oversleeping
8. Loss of interest in activities once enjoyed
9. Appetite changes, especially a craving for foods high in carbohydrates
10. Weight gain
11. Difficulty concentrating and processing information

Spring and summer SAD (summer depression)
Symptoms of summer-onset seasonal affective disorder include:

1. Anxiety
2. Insomnia
3. Irritability
4. Agitation
5. Weight loss
6. Poor appetite
7. Increased sex drive

In rare cases, people with seasonal affective disorder don't have depression-like symptoms. Instead, they have symptoms of mania or hypomania, a less intense form of mania, during the summer. This is sometimes called reverse SAD.

Symptoms of reverse SAD include:

1. Increased social activity
2. Hyperactivity
3. Unbridled enthusiasm out of proportion to the situation.

Mania: a phase of mental disorder characterized by an expansive emotional state, elation, hyperactivity, hyperirritability, over talkativeness, flight of ideas, and increased motor activity. Hypomania: mania of moderate type^[11]

Diagnostic Criteria for SAD:

According to the American Psychiatric Association, Treatment of Psychiatric Disorders, Third Edition, p.1296, for a diagnosis to qualify as Seasonal Affective disorder, it must meet the following criteria.

A. There has been a regular temporal relationship between the onset of major depressive episodes in bipolar I and bipolar II disorder or depressive disorder recurrent, and a particular time of the year (eg. Regular appearance of the major depressive episode in the fall or winter.

B. Full remissions ( or a change from depression to mania or hypomania) also occur at a characteristic time of the year (e.g. depression disappears in the spring).

C. In the last two years, two major depressive episodes have occurred that demonstrate the temporal seasonal relationships defined in criteria A and B, and no nonseasonal major depressive episodes have occurred during that same period.

D. Seasonal major depressive episodes (as described above) substantially outnumber depressive episodes than may have occurred over the individual’s lifetime

Treatment

Another type of light therapy lamp

There are many different treatments for classic (winter-based) seasonal affective disorder, including light therapies, medication, ionized-air reception, cognitive-behavioral therapy, and carefully timed supplementation of the hormone melatonin.

Bright light treatments are common although as many as 19% of patients stop use because of the inconvenience.^[3] 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.^[8] 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.^[3] Many patients use the light box in the morning, however it has not been proven any more effective than any other time of day.^[8] Discovering the best schedule is essential because up to 69% of patients find it inconvenient.^[3] 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.^[3] When compared in a study to negative air ionization, bright light was proven to be 57.1% effective vs. dawn simulation, 49.5%.^[12] Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks.^[3] 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.^[2]

SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Bupropion is also effective as a prophylactic.^[4] Effective antidepressants are fluoxetine, sertraline, or paroxetine.^[2][13] Both fluoxetine and light therapy are 67% effective in treating SAD according to direct head-to-head trials.^[2] Negative air ionization, involving the release of charged particles into the sleep environment, has also been found effective with a 47.9% improvement.^[12] Depending upon the patient, one treatment (ie. lightbox) may be used in conjunction with another therapy (ie. medication).^[2]

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 sync, and treat it with melatonin in the afternoon. Correctly timed melatonin administration shifts the rhythms of several hormones en bloc.^[14]

Throughout the world

The Nordic countries

Winter depression (or winter blues) is a common slump in the mood of inhabitants of the Nordic countries. Doctors estimate that about 20% of all inhabitants 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).^[15]

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.^[16] 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.^[17]

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%^[18] for subsyndromal SAD.

Ireland

Around one Irish person in five is 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. ^[19]

SAD and Bipolar

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

Famous sufferers

• Science fiction-fantasy author Barbara Hambly suffered with undiagnosed SAD for many years and speaks freely of it.^[21]
• Monty Don, a British gardner and TV presenter.

See also

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

References

 22 Gabbard, Glen O., Treatment of Pyschiatric Disorders, Third Edition, Volume 2., American Psychiatric Publishing, Washington, DC, 2001. p. 1296.

External links

• Seasonal Affective Disorder at the Open Directory Project
• Seasonal Depression Can Accompany Summer Sun Reverse SAD article at The New York Times
• Seasonal Affective Disorder - The Basics on ScienceBlogs