Seasonal affective disorder: Wikis

  
  

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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,[1] 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".[2]

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."[3] The condition in the summer is often referred to as Reverse Seasonal Affective Disorder, and can also include heightened anxiety.[4] It has been estimated that 1.5-9% of adults in the US experience SAD.[5]

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,[6] and carefully timed supplementation of the hormone melatonin.[7]

Contents

Symptoms

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 a decreased sex drive.[4] RSAD can also manifest depression, which makes it difficult to diagnose this rare affliction.

Diagnostic Criteria

According to the American Psychiatric Association DSM-IV,[8] 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[4] describes three types of Seasonal Affective Disorder, each with its own set of symptoms.

Physiology

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-light therapy.[9] SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N) where the rate of SAD is 9.5%[10] Cloud cover may contribute to the negative effects of SAD.[5]

The symptoms of SAD mimic those of dysthymia or even major depressive disorder. 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.[5] At times, patients may not feel depressed, but rather lack energy to perform everyday activities.[9]

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,[11] although this has been disputed.[12] 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.[13] 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.[15] 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.[16]

Origin

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. [17] 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.[17]

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

One type of light therapy lamp

There are many different treatments for classic (winter-based) seasonal affective disorder, including light therapy, medication, ionized-air administration, cognitive-behavioral therapy and carefully timed supplementation[18] 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.[19] Light therapy often includes the use of a lightbox which emits far more lumens than a customary incandescent lamp. Bright white light, or "full spectrum" light at 10,000 lux is historically preferred, although blue (2,500 lux with wavelength at 480 nm) and low intensity green light therapy (350 lux with wavelength at 500 nm) are also used.[20][21]

Bright light therapy is effective at doses of 2,500–10,000 lux,[14] 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.[10] Green light therapy at doses of 350 lux produces melatonin supression and phase shifts equivalent to 10,000 lux bright light therapy.[20][22] 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.[23] 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.[10]

Dawn simulation has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy.[10] When compared in a study to negative air ionization, bright light was proven to be 57.1% effective vs. dawn simulation, 49.5%.[6] Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks.[10] 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.[9]

Light therapy can also consist of exposure to sunlight, either in the form of spending more time outside [24], or using a computer-controlled mirror device called a heliostat to reflect sunlight into the windows of a home or office.[25][26]

SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Bupropion is also effective as a prophylactic.[5] Effective antidepressants are fluoxetine, sertraline, or paroxetine.[9][27] 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.[28] Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment.[9]

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).[29][30][31] Depending upon the patient, one treatment (ie. lightbox) may be used in conjunction with another therapy (ie. medication).[9]

Modafinil may be also an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.[32]

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.[18]

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.[33] [34] [35] [36] However, one study did not show a link between vitamin D levels and depressive symptoms in elderly Chinese.[37]

Incidence

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).[38] 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.[39] 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.[40] 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.[41] Fish is high in vitamin D. Fish also contains docosahexaenoic acid (DHA), which has been shown to help with a variety of neurological dysfunction.[42]

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%[43] 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.[44] An estimated 10% of the population in the Netherlands suffers from SAD.[45]

SAD and Bipolar Disorder

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

See also

References

  1. ^ Seasonal Depression can Accompany Summer Sun. Ivry, Sara. The New York Times. Retrieved September 6, 2008
  2. ^ Lurie, Stephen J.; et al. (November 2006). "Seasonal Affective Disorder". American Family Physician (American Academy of Family Physicians) 74 (9): 1521–4. PMID 17111890. http://www.aafp.org/afp/20061101/1521.html. Retrieved 2009-07-26. 
  3. ^ U.S. National Library of Medicine
  4. ^ a b c Seasonal Affective Disorder by Mayo Clinic
  5. ^ a b c d Modell, Jack; Rosenthal NE, Harriett AE, Krishen A, Asgharian A, Foster VJ, Metz A, Rockett CB, Wightman DS (2005). "Seasonal affective disorder and its prevention by anticipatory treatment with bupropion XL Biological Psychiatry". Biological psychiatry 58 (8): 658–667. doi:10.1016/j.biopsych.2005.07.021. PMID 16271314. 
  6. ^ a b Terman, M.; Terman, J.S. (2006). "Controlled Trial of Naturalistic Dawn Simulation and Negative Air Ionization for Seasonal Affective Disorder". American Journal of Psychiatry 163 (12): 2126–2133. doi:10.1176/appi.ajp.163.12.2126. 17151164. PMID 17151164. 
  7. ^ "Properly Timed Light, Melatonin Lift Winter Depression by Syncing Rhythms" (Science Update). National Institute of Mental Health. 2006-05-01. http://www.nimh.nih.gov/science-news/2006/properly-timed-light-melatonin-lift-winter-depression-by-syncing-rhythms.shtml. Retrieved 2009-08-30. 
  8. ^ Gabbard, Glen O. Treatment of Psychiatric Disorders (Third edition, Volume 2 ed.). Washington, DC: American Psychiatric Publishing. pp. 1296. 
  9. ^ a b c d e f Lam, RW; Levitt AJ, Levitan RD, Enns MW, Morehouse R, Michalak EE, Tam EM (2006). "The Can-SAD Study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder". American Journal of Psychiatry 163 (5): 805–812. doi:10.1176/appi.ajp.163.5.805. PMID 16648320. 
  10. ^ a b c d e Avery, D H; Eder DN, Bolte MA, Hellekson CJ, Dunner DL, Vitiello MV, Prinz PN (2001). "Dawn simulation and bright light in the treatment of SAD: a controlled study". Biological Psychiatry 50 (3): 205–216. doi:10.1016/S0006-3223(01)01200-8. PMID 11513820. 
  11. ^ Johansson, C; Smedh C, Partonen T, Pekkarinen P, Paunio T, Ekholm J, Peltonen L,Lichtermann D, Palmgren J, Adolfsson R, Schalling M (2001). "Seasonal affective disorder and serotonin-related polymorphisms". Neurobiology of Disease 8 (2): 351–357. doi:10.1006/nbdi.2000.0373. PMID 11300730. 
  12. ^ Johansson, C; Willeit M, Levitan R, Partonen T, Smedh C, Del Favero J, Bel Kacem S, Praschak-Rieder N,Neumeister A, Masellis M, Basile V, Zill P, Bondy B, Paunio T, Kasper S, Van Broeckhoven C, Nilsson LG,Lam R, Schalling M, Adolfsson R. (2003). "The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality". Psychological Medicine 33 (5): 785–792. doi:10.1017/S0033291703007372. PMID 12877393. 
  13. ^ Uz, T; Manev, H (2001). "Prolonged swim-test immobility of serotonin N-acetyltransferase (AANAT)-mutant mice". Journal of Pineal Research 30 (3): 166–170. doi:10.1034/j.1600-079X.2001.300305.x. PMID 11316327. 
  14. ^ a b Avery, D. H.; Kizer D, Bolte MA, Hellekson C (2001). "Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure". Acta Psychiatrica Scandinavica 103 (4): 267–274. doi:10.1034/j.1600-0447.2001.00078.x. PMID 11328240. 
  15. ^ Leppämäki, Sami; Haukka J, Lonnqvist J, Partonen T (2004). "Drop-out and mood improvement: a randomised controlled trial with light exposure and physical exercise". BMC Psychiatry 4 (22): 22. doi:10.1186/1471-244X-4-22. PMID 15306031. 
  16. ^ "Breakthroughs tips and trends: November 7th - Times Online". www.timesonline.co.uk. http://www.timesonline.co.uk/tol/life_and_style/health/article5106718.ece. Retrieved 2008-11-10. 
  17. ^ a b Nesse, Randolphe M; Williams, George C. Why We Get Sick (First ed.). New York: Vintage Books. pp. 290. 
  18. ^ a b Bhattacharjee, Y (2007). "Psychiatric research. Is internal timing key to mental health?". Science (New York, N.Y.) 317 (5844): 1488–90. doi:10.1126/science.317.5844.1488. PMID 17872420. http://www.ohsu.edu/ohsuedu/academic/som/images/Al-Lewy-Science.pdf. 
  19. ^ Howland, RH (2009). "Somatic therapies for seasonal affective disorder.". J Psychosoc Nurs Ment Health Serv 47 (1): 17–20. PMID 19227105. 
  20. ^ a b Saeeduddin Ahmed, Neil L Cutter, Alfred J. Lewy, Vance K. Bauer, Robert L Sack and Mary S. Cardoza (1995). "Phase Response Curve of Low-Intensity Green Light in Winter Depressives.". Sleep Research 24: 508. ""The magnitude of the phase shifts [using low-level green light therapy] are comparable to those obtained using high-intensity white light in winter-depressives."". 
  21. ^ Strong, RE; Marchant, BK; Reimherr, FW; Williams, E; Soni, P; Mestas, R (2009). "Narrow-band blue-light treatment of seasonal affective disorder in adults and the influence of additional nonseasonal symptoms.". Depress Anxiety. 26 (3): 273–8. PMID 19016463. "BROKEN/DEAD LINK". 
  22. ^ Michel A. Paul, James C. Miller, Gary Gray, Fred Buick, Sofi Blazeski and Josephine Arendt (July 2007). "Circadian Phase Delay Induced by Phototherapeutic Devices.". Sleep Research 78 (7): 645–652. http://www.ingentaconnect.com/content/asma/asem/2007/00000078/00000007/art00001. 
  23. ^ Tuunainen, Arja; Kripke, Daniel F; Endo, Takuro; Tuunainen, Arja (2004). Light therapy for non-seasonal depression. doi:10.1002/14651858.CD004050.pub2. 
  24. ^ Beck, Melinda. (December 1, 2009) "Bright Ideas for Treating the Winter Blues". (Section title: "Exercise outdoors") The Wall Street Journal. http://online.wsj.com/article/SB10001424052748703300504574567881192085174.html?mod=rss_Today%27s_Most_Popular
  25. ^ "Applications: Health". Practical Solar. http://www.practicalsolar.com/applications.html. Retrieved 2009-06-09. 
  26. ^ "Grab the Sun With Heliostats". New York House. 2009-06-01. http://www.newyorkhousemagazine.com/pages/full_story?page_label=home_main_top&id=2631630&widget=push&instance=home_green_future&article-Grab%20the%20Sun%20With%20Heliostats%20=&open=&. Retrieved 2009-12-08. 
  27. ^ Moscovitch, A; Blashko CA, Eagles JM, Darcourt G, Thompson C, Kasper S, Lane RM (2004). "A placebo-controlled study of sertraline in the treatment of outpatients with seasonal affective disorder". Psychopharmacology 171 (4): 390–397. doi:10.1007/s00213-003-1594-8. PMID 14504682. 
  28. ^ Lam, Raymond W.; Anthony J. Levitt, Robert D. Levitan, et al. (May 2006). "The Can-SAD Study: A Randomized Controlled Trial of the Effectiveness of Light Therapy and Fluoxetine in Patients With Winter Seasonal Affective Disorder" (PDF, full text). Am J Psychiatry 163 (163): 805–812. doi:10.1176/appi.ajp.163.5.805. http://day-lights.com/light-therapy-news/downloads/can-sad-study-wp.pdf. Retrieved 2008-09-30. 
  29. ^ Terman, M.; Terman, J. S. (2006). "Controlled Trial of Naturalistic Dawn Simulation and Negative Air Ionization for Seasonal Affective Disorder". American Journal of Psychiatry 163: 2126. doi:10.1176/appi.ajp.163.12.2126. 
  30. ^ Terman, M. (1998). "A Controlled Trial of Timed Bright Light and Negative Air Ionization for Treatment of Winter Depression". Archives of General Psychiatry 55: 875. doi:10.1001/archpsyc.55.10.875 (inactive 2009-10-07). 
  31. ^ Terman, M; Terman, JS (1995). "Treatment of seasonal affective disorder with a high-output negative ionizer.". Journal of alternative and complementary medicine 1 (1): 87–92. doi:10.1089/acm.1995.1.87. PMID 9395604. 
  32. ^ Lundt, L (2004). "Modafinil treatment in patients with seasonal affective disorder/winter depression: an open-label pilot study". Journal of Affective Disorders 81: 173. doi:10.1016/S0165-0327(03)00162-9. 
  33. ^ http://newfoundlandnews.blogspot.com/2008/01/sadness-seasonal-affective-disorder.html
  34. ^ http://www.nowfoods.com/M092051.htm "Vitamin D Deficiency Linked to Low Mood State and Lowered Intellectual Ability in Elderly" 2006
  35. ^ Lansdowne, AT; Provost, SC (1998). "Vitamin D3 enhances mood in healthy subjects during winter.". Psychopharmacology 135 (4): 319–23. doi:10.1007/s002130050517. PMID 9539254. 
  36. ^ Gloth Fm, 3rd; Alam, W; Hollis, B (1999). "Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder.". The journal of nutrition, health & aging 3 (1): 5–7. PMID 10888476. 
  37. ^ http://www.sciencedaily.com/releases/2009/03/090317142847.htm "Vitamin D May Not Be The Answer To Feeling SAD" Mar 2009
  38. ^ Jordanes, Getica, ed. Mommsen, Mon. Germanae historica, V, Berlin, 1882.
  39. ^ Magnusson, Andres; Axelsson, Johann; Karlsson, Mikael M.; Oskarsson, Högni (February 2000). "Lack of Seasonal Mood Change in the Icelandic Population: Results of a Cross-Sectional Study". Am J Psychiatry (American Psychiatric Association) 157 (2): 234–238. doi:10.1176/appi.ajp.157.2.234. PMID 10671392. http://ajp.psychiatryonline.org/cgi/content/full/157/2/234. Retrieved 2007-11-27. 
  40. ^ sson A, Magnú Axelsson J (1993). "The prevalence of seasonal affective disorder is low among descendants of Icelandic emigrants in Canada". Arch. Gen. Psychiatry 50 (12): 947–51. PMID 8250680. 
  41. ^ Cott, Jerry; Joseph R. Hibbeln (February 2001). "Lack of Seasonal Mood Change in Icelanders" (Letter to the Editor). Am J Psychiatry (American Psychiatric Association) 158 (158): 328. doi:10.1176/appi.ajp.158.2.328. http://ajp.psychiatryonline.org/cgi/content/full/158/2/328. Retrieved 2008-09-02. "Thus, high levels of fish consumption should be considered a potential etiology for the finding of a lack of seasonal affective disorder among the Icelandic population.". 
  42. ^ Horrocks, LA; Yeo, YK (1999). "Health benefits of docosahexaenoic acid (DHA)". Pharmacological research : the official journal of the Italian Pharmacological Society 40 (3): 211–25. doi:10.1006/phrs.1999.0495. PMID 10479465. 
  43. ^ Seasonal Affective Disorder and Latitude
  44. ^ BreakingNews.ie - One in five suffers from SAD
  45. ^ Elsevier – Dark Days: Winter Depression (in Dutch, easy to translate to English with google translate (or anything like that)
  46. ^ "Depression" (PDF). Mood Disorders Society of Canada. http://www.mooddisorderscanada.ca/documents/Consumer%20and%20Family%20Support/Depression.pdf. Retrieved 2009-08-08. 

External links


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,[1] 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".[2]

Once regarded sceptically by the experts, seasonal affective disorder is now well established. Epidemiological studies estimate that its prevalence in the adult population ranges from 1.4 percent (Florida) to 9.7 percent (New Hampshire).[3]

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 may also feel depressed. Though symptoms can be severe, they usually clear up."[4] The condition in the summer is often referred to as Reverse Seasonal Affective Disorder, and can also include heightened anxiety.[5]

SAD was first formally described and named in 1984 by Norman E. Rosenthal and colleagues at the National Institute of Mental Health.[6][7]

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,[8] and carefully timed supplementation of the hormone melatonin.[9]

Contents

Symptoms

Symptoms of SAD may consist of difficulty waking up in the morning, morning sickness, 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, pessimistic feelings of hopelessness, and lack of pleasure which characterize a person suffering from this disorder.[citation needed]

People who experience summer SAD (spring and summer depression) show symptoms of classic depression including insomnia, anxiety, irritability, decreased appetite, weight loss, social withdrawal, and a decreased sex drive.[5] Additionally, many patients are unable to cope with the increased temperatures during spring and summer.

Diagnostic criteria

According to the American Psychiatric Association DSM-IV criteria,[10] Seasonal Affective Disorder is not regarded as a separate disorder. It 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 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[5] describes three types of SAD, each with its own set of symptoms.

Physiology

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-light therapy.[11] SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N) where the rate of SAD is 9.5%.[12] Cloud cover may contribute to the negative effects of SAD.[13]

The symptoms of SAD mimic those of dysthymia or even major depressive disorder. 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.[13] At times, patients may not feel depressed, but rather lack energy to perform everyday activities.[11]

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,[14] although this has been disputed.[15] 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.[16] 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% SAD) of the U.S. population.[17] 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.[18] 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.[19]

History

SAD was first systematically reported and named in the early 80’s by Norman E. Rosenthal, M.D., and his associates at the National Institute of Mental Health (NIMH). Rosenthal was initially motivated by his desire to discover the cause of his own experience of depression during the dark days of the northern US winter. He theorized that the lesser amount of light in winter was the cause. Rosenthal and his colleagues then documented the phenomenon of SAD in a placebo-controlled study utilizing light therapy.[7][20] A paper based on this research was published in 1984. Although Rosenthal's ideas were initially greeted with skepticism, SAD has become well recognized, and his 1993 book, Winter Blues[21] has become the standard introduction to the subject.[22]

Research on SAD in the United States began in 1970 when Herb Kern, a research engineer, had also noticed that he felt depressed during the winter months. Kern suspected that scarcer light in winter was the cause and discussed the idea with scientists at the NIMH who were working on bodily rhythms. They were intrigued, and responded by devising a lightbox to treat the Kern’s depression. Kern felt much better within a few days of treatments, as did other patients treated in the same way.[7]

Origin

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.[23] 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.[23]

If these interpretations are correct, SAD would not be a dysfunction or disorder, but rather a normal and expected response to seasonal changes.

Treatment

There are many different treatments for classic (winter-based) seasonal affective disorder, including light therapy, medication, ionized-air administration, cognitive-behavioral therapy and carefully timed supplementation[24] 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.[25] Light therapy uses a lightbox which emits far more lumens than a customary incandescent lamp. Bright white "full spectrum" light at 10,000 lux, blue light at a wavelength of 480 nm at 2,500 lux or green light at a wavelength of 500 nm at 350 lux are used, with the first-mentioned historically preferred.[26][27]

Bright light therapy is effective[17] 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[12] for 30–60 minutes. A 1995 study showed that green light therapy at doses of 350 lux produces melatonin suppression and phase shifts equivalent to 10,000 lux bright light therapy in winter depressives.[26] A study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination.[28] Discovering the best schedule is essential. One study has shown that up to 69% of patients find lightbox treatment inconvenient and as many as 19% stop use because of this.[12]

Dawn simulation has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy.[12] When compared in a study to negative air ionization, bright light was shown to be 57% effective vs. dawn stimulation 50%.[8] Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks.[12] 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.[11]

Light therapy can also consist of exposure to sunlight, either by spending more time outside[29] or using a computer-controlled heliostat to reflect sunlight into the windows of a home or office.[30][31]

SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Bupropion is also effective as a prophylactic.[13] Effective antidepressants are fluoxetine, sertraline, or paroxetine.[11][32] 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.[33] Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment.[11]

Negative air ionization, which involves releasing charged particles into the sleep environment, has been found effective with a 47.9% improvement if the negative ions are in sufficient density (quantity).[34][35][36] Depending upon the patient, one treatment (e.g., lightbox) may be used in conjunction with another (e.g., medication).[11]

Modafinil may be an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.[37]

Alfred J. Lewy of Oregon Health & Science University and others see the cause of SAD as a misalignment of the sleep-wake phase with 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.[24]

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.[38][39][40][41] However, one study did not show a link between vitamin D levels and depressive symptoms in elderly Chinese.[42]

Incidence

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).[43] 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.[44] 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.[45] 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.[46] Fish is high in vitamin D. Fish also contains docosahexaenoic acid (DHA), which has been shown to help with a variety of neurological dysfunction.[47]

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%[48] 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.[49] An estimated 10% of the population in the Netherlands suffer from SAD.[50]

SAD and bipolar disorder

Most people with SAD experience major depressive disorder, but as many as 20% may have or may go on to develop a bipolar disorder (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.[51] In these cases, people with SAD may experience depression during the winter and hypomania in the summer.

See also

References

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