Beyond the “Winter Blues”: The Clinical Reality and Complexities of Seasonal Affective Disorder

Often given as a shorthand explanation for why certain individual may feel sluggish or unmotivated during certain times of the year, seasonal affective disorder (SAD) is more complex and clinically significant than some may believe. SAD is a subtype, or subtype specifier, of a recurrent mood disorder, typically clinical depression or major depressive disorder.^1-3

Also known as seasonal depression, it is largely characterized by recurring, seasonal episodes of depression that follow a predictable annual pattern, but it is not a clinical diagnosis unto itself, according to the Diagnostic and Statistical Manual of Mental Disorders.⁴

At the same time, the disorder remains misunderstood from misconceptions that often obscure its underlying biological and psychological mechanisms. Although the disorder shares features with major depressive disorder, it is distinguished by its cyclical nature and the unique treatments that target its underlying causes. An accurate understanding of SAD requires attention to the clinical features that define the condition and the day-to-day realities that shape how it feels.

Distinguising SAD From Typical Depression

Although most associated with the darker months of fall and winter, SAD can occur in other seasons as well, challenging the misconception that it is merely a response to cold weather.

“The stereotypic thing we think about is fall and winter with depressive symptom onset and then as we get to the spring and the summertime, a reliable remission of those symptoms,” explained Craig N. Sawchuk, PhD, LP, cochair of the Division of Integrated Behavioral Health and of Clinical Practice, Department of Psychiatry and Psychology, Mayo Clinic, in an interview with The American Journal of Managed Care^® (AJMC^®). “But the same thing can actually happen when we establish a seasonal pattern where it’s reversed; that in the fall and winter months, people reliably feel better and in the spring and summer, they feel worse.”

Experts further emphasize that SAD is not simply “winter blues.” Although many people experience mild mood changes when days grow shorter, SAD’s symptoms are known to occur in at least 2 seasons and in a reliable pattern, explains Sawchuck. They also occur consistently for at least 2 consecutive years, during which an individual experiences no nonseasonal depressive episodes and the seasonal episodes outnumber the nonseasonal episodes, noted Gabriella I. Farkas, MD, PhD, founder of Pearl Behavioral Health, to AJMC.

From a plain-language standpoint, SAD can be understood as a predictable form of recurring depression. Persons may feel pervasively down most days for all days; suffer from secondary hypersomnia, or an excess of debilitating nonrestorative sleep and daytime drowsiness; be increasingly irritable and prone to mood changes (feelings of “blah,” noted Sawchuk); and crave carbohydrates and/or experience changes to their appetite and weight.^3-6

In contrast, major depression can occur at any time and it does not follow a season pattern; it can be continuous or occasional. Its triggers also differ from SAD and include stress, life events, health problems, or genetics, and its sleep and appetite changes vary either up or down, explained Farkas. Sawchuk added that in contrast to persons with seasonal depression, individuals living with typical depression more often suffer from insomnia and difficulty functioning and are more self-critical to the point of being harsh on themselves.

Vulnerability Risk Factors

The appearance of SAD is known to be related to changes in daylight, with individuals having a higher risk of developing it when they live at a higher latitude either north or south of the equator.^4,7

Living at or near the equator means total daylight of 12 hours or very close to that year-round⁸; moving further north, daylight hours increase following the summer and winter solstice—in contrast to areas south of the equator, in which daylight hours decrease following each solstice. In particular, when total daily daylight hours decrease, the circadian rhythm is interrupted and as a result there are adverse impacts to the sleep-wake cycle, hormone release, and quality of daily life among others.⁹ For example, previous research shows that among individuals living with SAD, their brains exhibit reduced serotonin levels, as well that total sunlight may be linked to molecules involved in regulating serotonin levels—so that their functioning is impaired at fewer daylight hours.¹⁰ Serotonin is a chemical in the brain that helps to regulate mood.

There is also disruption and dysregulation of dopamine neurotransmitters, another regulator of mood, the sleep/wake cycle, and eating, explained Sawchuk. In turn, these disruptions can adversely affect production of melatonin, in that the impact on dopamine production can go on to impact norepinephrine, which is involved in producing and releasing melatonin.¹¹ He also noted nascent research on how the retina could be involved, in that in people with SAD it is not as reactive to changes in light, and that brain structure–wise, the suprachiasmatic nucleus of the hypothalamus, best known to regulate most circadian rhythms in the body, is disturbed.¹²

Farkas explained, too, that brain activity may be implicated, in that people with SAD may have brains that are more sensitive to light, meaning shorter days can directly affect mood and energy. “Regions of the brain that handle mood, emotions, and reward may act differently in SAD,” she told AJMC. “These changes come and go with the seasons, unlike in other depressions.”

Treatment Strategies

The approach to treating SAD incorporates many mainstays of mental health care: lifestyle factors, such as maintaining a regular sleep and activity schedule; evidence-based psychotherapy¹³; and pharmacotherapy,¹⁴ according to previous research, as well as Sawchuk and Farkas.

Exposure to sunlight, which can be accomplished by going outside or simply being near a window, and vitamin D are recommended for winter-pattern SAD; vitamin D is recommended because deficient levels of it are thought to have an adverse impact on serotonin levels. There are no treatments that specifically target summer-pattern SAD.¹³ Psychotherapy, in the forms of cognitive-behavioral therapy and interpersonal therapy, is a prominent way to help patients change how they think about themselves and their environment, as well as identify stressors and coping skills.^10,13,14 Antidepressant medications are also used, either alone or with talk therapy, and in the setting of SAD, they work to rebalance the brain chemicals that may have led to SAD. In particular, selective serotonin reuptake inhibitors may be used because of reduced serotonin levels.^10,13

There is also an additional treatment for SAD that is both a unique and highly effective intervention: bright white light therapy using an artificial source or special lamp or light box. A SAD treatment mainstay since the 1980s, the current recommended amount is 10,000 lux every day for 15 to 20 minutes in the morning, and ultraviolet light is not included—meaning the treatment is safe for most patients.¹³ This first-line treatment is recommended at this brightness level and length of time, because with boxes of a reduced strength, more time would be needed and the treatment is not as effective.

According to Sawchuk, guidelines for this treatment include the following recommendations:

• Start 2 weeks ahead of when SAD symptoms typically present themselves
• Pair the light with early morning activities, typically those that take place within the hour of waking
• Keep the box at arm’s length, ideally 3 to 5 feet
• Keep the eyes open, but do not stare directly at the light
• Use the light box every day throughout the season of SAD until there is a noticeable improvement in mood

Most important is to seek help early and to talk to a professional before symptoms become severe, and so that the condition is not confused with another mental health condition, such as bipolar disorder, or medical condition, such as low thyroid function, Farkas explained. Also, track response to treatment and adjust treatment as needed.

The complexity of SAD—in which neurochemistry, geography, and daylight intersect—means that effective treatment relies on a multimodal, individualized approach that recognizes the condition’s predictable cyclical nature.

References

1. Diagnosing seasonal affective disorder. The REACH Institute. March 16, 2024. Accessed November 29, 2025. https://thereachinstitute.org/diagnosing-seasonal-affective-disorder
2. Khan M. Are you S.A.D.? what to know about the “winter blues,” depression, and seasonal affective disorder. WVU Medicine Golisano Children's. January 4, 2024. Accessed November 29, 2025. https://childrens.wvumedicine.org/blog/are-you-s-a-d-what-to-know-about-the-winter-blues-depression-and-seasonal-affecti
3. Berg S. What doctors wish patients knew about seasonal affective disorder. American Medical Association. October 31, 2025. Accessed November 29, 2025. https://www.ama-assn.org/public-health/behavioral-health/what-doctors-wish-patients-knew-about-seasonal-affective-disorder
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5. Summer JV. Seasonal affective disorder: sleep tips to beat the winter blues. Sleep Foundation. Updated July 23, 2025. Accessed November 30, 2025. https://www.sleepfoundation.org/circadian-rhythm/seasonal-affective-disorder
6. Seasonal affective disorder (SAD). Mental Health America. Accessed November 30, 2025. https://mhanational.org/conditions/seasonal-affective-disorder-sad/
7. Williamson L. As winter approaches, seasonal depression may set in for millions. November 30, 2022. Accessed November 30, 2025. https://www.heart.org/en/news/2022/11/30/as-winter-approaches-seasonal-depression-may-set-in-for-millions
8. What causes the seasons? National Weather Service. Accessed November 30, 2025. https://www.weather.gov/fsd/season
9. Understanding seasonal affective disorder. Mental Health Center. September 3, 2025. Accessed November 30, 2025. https://www.mentalhealthctr.com/how-seasonal-affective-disorder-impacts-mental-health
10. Seasonal affective disorder. National Institute of Mental Health. Updated 2023. Accessed November 30, 2025. https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder
11. Vandergriendt C. What’s the difference between dopamine and serotonin? Healthline. July 16, 2020. Accessed November 30, 2025. https://www.healthline.com/health/dopamine-vs-serotonin#sleep
12. Ma MA, Morrison EH. Neuroanatomy, nucleus suprachiasmatic. StatPearls/National Library of Medicine. January 2025. Accessed November 30, 2025. https://www.ncbi.nlm.nih.gov/books/NBK546664/
13. Seasonal affective disorder. Johns Hopkins Medicine. Accessed December 2, 2025. https://www.hopkinsmedicine.org/health/conditions-and-diseases/seasonal-affective-disorder
14. How to manage seasonal depression. Aetna. Accessed December 2, 2025. https://www.aetna.com/health-guide/how-to-manage-seasonal-depression.html