Editing Seasonal affective disorder (section)

==Pathophysiology==
Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-[[light therapy]].<ref name = "Lam">{{cite journal | vauthors = Lam RW, Levitt AJ, Levitan RD, Enns MW, Morehouse R, Michalak EE, Tam EM | title = The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder | journal = The American Journal of Psychiatry | volume = 163 | issue = 5 | pages = 805–12 | date = May 2006 | pmid = 16648320 | doi = 10.1176/appi.ajp.163.5.805 }}</ref> SAD is measurably present at latitudes in the [[Arctic Circle|Arctic region]], such as northern [[Finland]] (around [[64 degrees north]] latitude), where the rate of SAD is 9.5%.<ref name = "Avery">{{cite journal | vauthors = Avery DH, Eder DN, Bolte MA, Hellekson CJ, Dunner DL, Vitiello MV, Prinz PN | title = Dawn simulation and bright light in the treatment of SAD: a controlled study | journal = Biological Psychiatry | volume = 50 | issue = 3 | pages = 205–16 | date = August 2001 | pmid = 11513820 | doi = 10.1016/S0006-3223(01)01200-8 | s2cid = 21123296 }}</ref> Cloud cover may contribute to the negative effects of SAD.<ref name = "Modell">{{cite journal | vauthors = Modell JG, Rosenthal NE, Harriett AE, Krishen A, Asgharian A, Foster VJ, Metz A, Rockett CB, Wightman DS | title = Seasonal affective disorder and its prevention by anticipatory treatment with bupropion XL | journal = Biological Psychiatry | volume = 58 | issue = 8 | pages = 658–67 | date = October 2005 | pmid = 16271314 | doi = 10.1016/j.biopsych.2005.07.021 | s2cid = 25662514 }}</ref> There is evidence that many patients with SAD have [[Delayed sleep phase disorder|a delay]] in their [[circadian rhythm]], and that bright light treatment corrects these delays which may be responsible for the improvement in patients.<ref name="search.proquest">{{cite journal | vauthors = Lam RW, Levitan RD | title = Pathophysiology of seasonal affective disorder: a review | journal = Journal of Psychiatry & Neuroscience | volume = 25 | issue = 5 | pages = 469–80 | date = November 2000 | pmid = 11109298 | pmc = 1408021 }}</ref>

The symptoms of it 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 people with the condition required hospitalization during one period of illness.<ref name = "Modell"/> At times, patients may not feel depressed, but rather lack energy to perform everyday activities.<ref name = "Lam"/>

Subsyndromal Seasonal Affective Disorder (s-SAD or SSAD) is a milder form of SAD experienced by an estimated 14.3% (vs. 6.1% SAD) of the U.S. population.<ref name = "Avery2">{{cite journal | vauthors = Avery DH, Kizer D, Bolte MA, Hellekson C | title = Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure | journal = Acta Psychiatrica Scandinavica | volume = 103 | issue = 4 | pages = 267–74 | date = April 2001 | pmid = 11328240 | doi = 10.1034/j.1600-0447.2001.00078.x | s2cid = 1342943 }}</ref> The blue feeling experienced by both those with SAD and with SSAD can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure.<ref name = "Leppämäki">{{cite journal | vauthors = Leppämäki S, Haukka J, Lönnqvist J, Partonen T | title = Drop-out and mood improvement: a randomised controlled trial with light exposure and physical exercise [ISRCTN36478292] | journal = BMC Psychiatry | volume = 4 | pages = 22 | date = August 2004 | pmid = 15306031 | pmc = 514552 | doi = 10.1186/1471-244X-4-22 | doi-access = free }}</ref> Connections between human mood, as well as energy levels, and the seasons are well documented, even in healthy individuals.<ref>{{cite journal | vauthors = Partonen T, Lönnqvist J | title = Bright light improves vitality and alleviates distress in healthy people | journal = Journal of Affective Disorders | volume = 57 | issue = 1–3 | pages = 55–61 | date = 2000 | pmid = 10708816 | doi = 10.1016/S0165-0327(99)00063-4 }}</ref>