Seasonal Affective Disorder: Can You Prevent Winter Depression?
Key Points
Seasonal affective disorder (SAD) is a form of major depression with episodes that recur at a particular time of year, most often fall and winter.
Winter depression can sometimes be prevented. Bupropion XL, started in the fall, is the only medication FDA-approved for this, and evidence for other preventive approaches is limited.
Light therapy, antidepressants, and SAD-specific CBT are all effective treatments, and CBT may reduce recurrence in later winters.
Vitamin D and melatonin are not established treatments for SAD.
People with bipolar disorder should start light therapy only with a clinician's guidance, due to the risk of triggering mania.
Seasonal affective disorder, also known as seasonal depression, is a condition that typically emerges in the fall or winter seasons, as the duration of daylight shortens. Because the winter variant is thought to be caused by reduced exposure to sunlight, many of the treatments are centered around replacing sunlight, or the effects of sunlight, using a few different strategies. For some individuals, medications may be necessary to prevent seasonal depression or recover full levels of functioning during depressive episodes. This article is meant to provide an overview of preventative measures that can be taken before seasonal depression sets in, as well as treatment options for those who are experiencing seasonal depression.
What Is Seasonal Affective Disorder?
Seasonal affective disorder (SAD) is considered a subtype of major depressive disorder, described by clinicians as major depressive disorder with a seasonal pattern. For most individuals who have seasonal affective disorder, episodes of depression occur during the fall and/or winter months, and subside in the spring and summer. However, a small number of individuals with seasonal affective disorder experience mood symptoms during the spring and summer, with improvement occurring in the fall and winter.
Those who experience winter SAD are more likely to have “atypical” symptoms, including hypersomnia (sleeping more than usual) and increased appetite, rather than insomnia and reduced appetite. This is in addition to the core symptoms of depression, such as persistently low mood, anhedonia (lack of interest or pleasure), lack of motivation, irritability, fatigue, poor concentration, feelings of hopelessness/helplessness, low self esteem, and sometimes, suicidal ideation. Individuals with the summer variant of SAD are more likely to experience typical symptoms of depression.
The prevalence of seasonal affective disorder varies worldwide, and is correlated with the distance from the equator. Estimates range from about 1.5% to 9%, depending on latitude, with U.S. studies finding higher rates in northern than southern locations. A 2025 meta-analysis of worldwide prevalence estimates of SAD showed a significant correlation between latitude and prevalence of SAD. So far, the effect of altitude or regional weather patterns on SAD has not been directly studied.
Why Do Shorter Days Affect Our Mood?
The short answer to this question is that we don’t really know. However, a large focus of research investigating the mechanism of seasonal affective disorder has centered on the effect of daylight on the circadian rhythm and neurotransmitters involved in mood regulation.
The circadian rhythm is a genetically programmed biological process that regulates the timing of natural sleep/wake cycles in humans, and is highly sensitive to the duration and timing of light exposure. Consistent with this light-sensitivity, the circadian rhythm varies depending on the season, such that humans can adapt to changes in duration of daylight. Coincident with this seasonal variation in the circadian rhythm are seasonal variations in the processes that regulate serotonin and dopamine signaling in the brain.
Serotonin is well known for its proposed role in regulation of mood, while dopamine plays important roles in learning, motivation, and responses to rewarding experiences (like eating food, for example). Individuals with SAD show different, and in some studies exaggerated, seasonal changes in serotonin signaling compared with healthy individuals. This suggests SAD may be caused by an abnormal response to seasonal changes in daylight, although the exact mechanism has not been established.
So far the association between seasonal variations in dopamine signaling and SAD has not been studied as extensively as serotonin signaling, although this remains an active area of research.
Preventative Interventions for Seasonal Depression
Several interventions have been studied for the prevention of seasonal depression in individuals who experience this condition, including light therapy, cognitive behavioral therapy (CBT), a melatonin-signaling modulator, and antidepressants. These preventative interventions largely mirror the interventions used to treat depressive episodes in seasonal depression.
Of the interventions that have been investigated, bupropion XL is the only medication FDA-approved for preventing seasonal depressive episodes. Starting light therapy before symptoms begin is supported mainly by small studies, however the evidence for preventative light-therapy, agomelatine and mindfulness-based cognitive therapy remains inconclusive. SAD-specific cognitive behavioral therapy has shown lower recurrence rates of SAD compared to light therapy when implemented during an episode of winter SAD, however the use of CBT-SAD for prevention is still an area of active research.
For individuals who experience a predictable pattern of depression each winter, the best time to develop a prevention plan is before symptoms typically begin.
Treatment Options for Seasonal Depression
Light Therapy for Seasonal Depression
Light therapy remains the first-line intervention for treatment of seasonal depressive episodes, meaning that it is supported by strong clinical evidence and is recommended as the initial treatment option. It is recommended that individuals start light therapy at the onset of depressive symptoms, usually in early to late fall, and continue until spring. Light therapy works best when administered within 30 minutes of waking up in the morning, and should be used daily, for 30 minutes. The intensity of light, and the distance of light from the eyes, are both essential to efficacy. Of note, individuals with bipolar disorder are at risk of a manic episode as a side effect of light therapy, therefore it is recommended that light therapy be monitored by a physician.
CBT for Seasonal Depression
Cognitive behavioral therapy for seasonal affective disorder (CBT-SAD) is an effective treatment for seasonal depression, with similar results when compared to light therapy. Interestingly, CBT-SAD may offer an additional benefit by preventing recurrence of future episodes of SAD in subsequent winters after the initial treatment, whereas light therapy is best used every winter.
Medications for Seasonal Depression
Very few of the medications currently available for MDD have been studied in the specific context of seasonal depression. Bupropion XL is FDA approved for the prevention of seasonal depressive episodes, but has not been studied in RCTs for treatment of a current episode of SAD. Fluoxetine and light therapy have shown similar response rates for treatment of SAD. Because SAD is a seasonal form of major depressive disorder, clinicians may also consider antidepressants used for nonseasonal MDD, although many have not been specifically studied in SAD.
TMS for Seasonal Depression
Transcranial Magnetic Stimulation (TMS) is a form of neuromodulation that is FDA-cleared for the treatment of MDD in adolescents and adults ages 15 and older. Very few studies have addressed the effectiveness of TMS for seasonal affective disorder specifically, however in a small retrospective study, patients with a seasonal pattern of MDD responded to TMS about as well as those with non-seasonal MDD. For more information about TMS for depression, see The Mind Grove TMS Center.
Lifestyle Interventions for Seasonal Depression
Spending time outdoors during daylight hours, maintaining a consistent sleep-wake schedule, and engaging in regular physical activity may also be helpful during the winter months. Although these strategies have not been studied as extensively as light therapy or other treatments specifically for SAD, each can support circadian regulation and overall mental health and can be used alongside established treatments.
Melatonin and Vitamin D for Seasonal Depression
The RCTs completed to date do not support the use of Vitamin D supplementation as a stand alone treatment for SAD. However, if you have had blood levels of Vitamin D taken, and are deficient in Vitamin D, it is worth speaking with your physician about supplementation.
Similarly, melatonin is not an established treatment for SAD due to inadequate research trials. One small study found that very low doses timed to an individual's internal clock improved symptoms. A separate trial in people with milder seasonal symptoms found that controlled-release melatonin improved sleep quality and energy, but did not show a clear benefit for mood.
When To Seek Professional Help
If you are experiencing symptoms of depression that interfere with your daily functioning, it is recommended that you speak with a clinician. Light therapy is best used with the guidance and supervision of your doctor, as there are potential risks for individuals with undiagnosed or known bipolar disorder. It is also important to schedule regular follow-ups with your physician, so that medication or other interventions can be discussed if light therapy is not effective for you.
Frequently Asked Questions
What is the difference between SAD and the "winter blues"?
SAD involves recurrent seasonal episodes with symptoms severe enough to meet criteria for major depression and significantly affect daily functioning. The “winter blues” describes milder seasonal changes in mood, energy, or sleep that do not meet criteria for a depressive episode.
Does living in a sunny, high-altitude state like Colorado affect SAD risk?
This has not been directly studied. SAD risk generally increases with latitude, but whether altitude or sunnier winters raise or lower risk is unknown.
Can SAD be prevented?
Bupropion XL, started in the fall before symptoms begin, has been shown to reduce the risk of a winter depressive episode in people with a history of SAD. Evidence for other preventive approaches is limited. People with recurrent seasonal depression can discuss a prevention plan with a clinician before fall.
How do I use a light box safely?
Light therapy typically involves sitting in front of a 10,000-lux light box for about 30 minutes each morning, shortly after waking, without staring directly into the light. Follow the manufacturer's instructions for distance. People with bipolar disorder, eye conditions, or who take medications that increase light sensitivity should speak with a clinician before starting.
When should I seek help?
A clinician can help if depressive symptoms interfere with work, relationships, or daily activities, or last more than two weeks. Anyone experiencing suicidal thoughts should call or text 988 or go to the nearest emergency department.
Megan Bowers, MD, PhD is a child, adolescent, and adult psychiatrist specializing in neurodevelopmental disorders, and is the founder of Bowers Integrative Psychiatry and CEO and Medical Director of The Mind Grove TMS Center. Her work focuses on integrative approaches to mental health, combining evidence-based medication management with lifestyle and mind–body interventions.
The information provided on this website is for educational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any condition. Please consult a qualified healthcare professional for individualized medical guidance. Use of this website does not establish a physician–patient relationship.
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If you or a family member are experiencing seasonal depression and you’d like to explore preventative treatments, a free 15-minute introductory call is a good place to start. This conversation allows you to share what you are observing and learn how an integrative approach can help.
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Selected References
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