Seasonal Affective Disorder
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Seasonal Affective Disorder

By Adam Dalkilic

A type of depression, seasonal affective disorder (SAD) manifests itself by the change in seasons. Most of the time, symptoms for SAD begin in the fall and continues through winter, but in rare cases symptoms may develop in the spring and can last through the summer1. Contrary to popular belief, SAD is not considered a unique type of depression; psychiatrists consider it a type of persistent depression that follows a seasonal pattern2.

Interestingly, the prevalence of SAD depends on geographic location. People who are living father from the equator are more susceptible to SAD3. Although geographic location plays a large role in SAD, studies have shown that gender also affects SAD’s prevalence. One study suggested that women are four times more likely to experience SAD than men are4.

It is thought that SAD like other depression types is caused by an imbalance of serotonin, which is a neurotransmitter used by neurons to communicate5. Vitamin D deficiency may play a role in serotonin imbalances that result in depressive symptoms6. When people stay inside during the winter, their production of Vitamin D decreases, as their contact with sunlight decreases. In addition, melatonin, a natural hormone in the brain may have a role in SAD. Because the brain produces more melatonin in dark environments, the lack of sunlight in fall-winter seasons spikes melatonin production. Increase in melatonin commonly creates drowsiness and fatigue7,8, People struggling to fall asleep use melatonin as a common over the counter (OTC) sleep aid. 

Most of the symptoms of SAD are related to sadness, fatigue, pessimism, and mood instability, but they also could include insomnia (i.e. difficulty falling asleep, staying asleep, or not having refreshing sleep), anxiety, and weight change9. After diagnosing a patient for SAD by looking for these symptoms and for a seasonal pattern, a psychiatrist usually resorts to psychotherapy, light therapy and/or antidepressant medications.

A famous study led in 1984 by Norman Rosenthal10 displayed the potential of light therapy in treating patients with SAD. In his experiment, 29 patients with SAD were exposed to a UV light, meant to simulate that of the sun. After they were treated with this light for an extended period of time, Rosenthal observed antidepressant effects11. Long after his team’s discovery, light therapy became a popular treatment for SAD, often administered along antidepressant medications. According to a meta-analysis that compared the effectiveness of antidepressants to light therapy, no significant difference were observed between the two treatment options, except that treatment was much more successful when the two options were combined12. Although more research needs to be done, light therapy remains an effective treatment option for SAD patients.

Used to treat most types of depression, antidepressant medications, like selective serotonin reuptake inhibitors (SSRIs), are thought to correct the chemical imbalances in the brain. One of the most commonly prescribed antidepressants are SSRIs. Put simply, they prolong duration serotonin stays in synapses by blocking reuptake into neurons13. This results in improved communication among neurons in the brain. Some commonly prescribed SSRIs include sertraline, fluoxetine, citalopram, escitalopram, and paroxetine. According to reviews on treatments for SAD, light therapy is preferred treatment choice for SAD patients, but antidepressants,14,15, and talk therapy might be necessary in treatment resistant SAD cases. There are case reports in medical literature about using TMS to treat SAD in patients who did not respond to light therapy or medications. Overall, SAD occurs most commonly in areas far from the equator, and it could cause sadness, mood swings, insomnia, significant weight change, sleepiness/fatigue, poor motivation, low energy, feelings of guilt, and even suicidal thoughts. People suffering from these symptoms should check with their healthcare providers to determine if their condition meets the criteria for a formal SAD diagnosis and follow their recommendations.

1 (2017, October 25). Seasonal affective disorder (SAD) – Symptoms and causes …. Retrieved December 16, 2020, from

2Sherri Melrose, “Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches”, Depression Research and Treatment, vol. 2015, Article ID 178564, 6 pages, 2015.

3 L. N. Rosen, S. D. Targum, M. Terman et al., “Prevalence of seasonal affective disorder at four latitudes,” Psychiatry Research, vol. 31, no. 2, pp. 131–144, 1990.

4 N. Rosenthal, “What is seasonal affective disorder? Answers from the doctor who first described the condition,” Dr. Rosenthal’s personal website,

5 B. McMahon, S. Andersen, M. Madsen et al., “P.1.i.037 Patients with seasonal affective disorder show seasonal fluctuations in their cerebral serotonin transporter binding,” European Neuropsychopharmacology, vol. 24, supplement 2, p. S319, 2014.

6 R. Anglin, Z. Samaan, S. Walter, and S. McDonald, “Vitamin D deficiency and depression in adults: systematic review and meta-analysis,” British Journal of Psychiatry, vol. 202, no. 2, pp. 100–107, 2013.

7 A. L. Miller, “Epidemiology, etiology, and natural treatment of seasonal affective disorder,” Alternative Medicine Review, vol. 10, no. 1, pp. 5–13, 2005.

8 National Health Service, “Seasonal Affective Disorder—Symptoms,” United Kingdom Government website,

9 R. Dryden-Edwards, Seasonal Depression SAD, emedicinehealth, San Clemente, Calif, USA, 2015,

10 Rosenthal NE, Sack DA, Gillin JC, et al. Seasonal Affective Disorder: A Description of the Syndrome and Preliminary Findings With Light Therapy. Arch Gen Psychiatry. 1984;41(1):72–80. doi:10.1001/archpsyc.1984.01790120076010

11 See above

12 Pierre A. Geoffroy, Carmen M. Schroder, Eve Reynaud, Patrice Bourgin,
Efficacy of light therapy versus antidepressant drugs, and of the combination versus monotherapy, in major depressive episodes: A systematic review and meta-analysis, Sleep Medicine Reviews, Volume 48, 2019, 101213, ISSN 1087-0792, (

13 Hyttel, J. (1994). Pharmacological characterization of selective serotonin reuptake inhibitors (SSRIs). International Clinical Psychopharmacology, 9(Suppl 1), 19–26.

14 Partonen, T., Lönnqvist, J. Seasonal Affective Disorder. Mol Diag Ther 9, 203–212 (1998).

15 See Footnote 12