In many regions of the world, winter means shorter days and longer nights, which can trigger feelings of sadness, apathy, fatigue, and even depression for many people. Often referred to as the “winter blues” or “winter depression,” this seasonal mood shift is a form of acute depression known as seasonal affective disorder (SAD). SAD doesn’t have its own entry in the Diagnostic Manual of Mental Disorders (DSM-5) but is classified under depression as Major Depressive Disorder with Seasonal Pattern.¹
The effects of SAD can range from disorienting to dangerous, depending on the individual. However, seasonal depression is a highly common and treatable form of depression. This guide will illuminate the common causes of SAD, the symptoms to be on the lookout for, and the most up-to-date treatments and preventive measures, many of which can be applied right at home.
SAD is an apt acronym for seasonal depression. Like other forms of depression, sadness or apathy (numbness or emptiness) most of the time is the most pervasive hallmark symptom. Other symptoms commonly associated with SAD include:³
The major differentiating factor between seasonal depression and major depression (the most commonly discussed form) is SAD’s seasonal aspect. If you experience these symptoms year-round, you are likely experiencing major depression; seasonal depression is confined to one season. While it’s most common to experience SAD in the winter, some people experience SAD in the summer, too.
In terms of summer SAD, a significantly less common form of acute seasonal depression, there are a handful of additional symptoms to be on the lookout for:³
SAD is much more commonly found in people who live in places far from the equator. People living in Alaska, Washington, or New England, for example, are more likely to develop SAD than people living in sunnier places like Florida, California, or Hawaii. Symptoms of seasonal depression, usually start presenting in young adulthood, and the disorder is significantly more common in women than men.²
In total, about 5% of American adults have diagnosable SAD, whereas a much larger number of people — between 10% and 20% — experience a milder form of the disorder that is not typically severe enough to disrupt one’s daily life. To receive a clinical diagnosis of SAD, you must experience:
Especially for those who already experience challenges related to mental health, the symptoms of SAD can be easy to miss or dismiss. However, if you do find yourself burdened by the sudden onset of seasonal depression, enlist the help of a trained healthcare provider, psychiatrist, psychologist, or therapist. In many cases, SAD is one part of a more complex mental health issue, and a professional will be able to help you work through them all for the best treatment.³
SAD is a subtype of major depressive disorder (or MDD). The bulk of contemporary research suggests that SAD is largely due to biochemical shifts that disrupt our internal clock and circadian rhythm. This means that our bodies have difficulties adjusting to seasonal changes, such as temperature and day length, which can lead to disturbances in our sleep, mood, and eating habits.²
Here are three of the biggest biochemical changes that occur with seasonal depression.
The primary symptoms associated with SAD are believed to be linked to an imbalance of serotonin (a neurotransmitter commonly associated with mood regulation) and melatonin (a hormone responsible for maintaining a normal sleep-wake cycle). This deficiency is triggered by a lack of sunlight exposure during the fall and winter months.² Since you need serotonin to create melatonin in the pineal gland, any kind of drop in serotonin associated with depression will also drop your melatonin levels, making it harder to sleep at night.
Less direct sun exposure can also result in lower levels of vitamin D, which can exacerbate symptoms commonly associated with SAD. Our bodies can only create vitamin D through the skin when directly exposed to sunlight, though we can also take supplements or consume foods rich in vitamin D. But shorter days mean fewer rays, resulting in lower baseline vitamin D levels.² This may explain why people living in cooler, darker areas are more prone to SAD.
Of the millions of Americans who suffer from seasonal depression, many don’t even realize they have the condition and never connect their sudden, typically unpleasant symptoms to the bigger underlying issue. Those most affected by SAD — and unfortunately those most likely to overlook it — are individuals who also suffer from another form of chronic mental illness, including bipolar disorder, ADHD, anxiety disorders (especially panic disorder), or eating disorders.²
The arrival of winter often means new limitations and additional stressors, which can produce a multitude of negative thoughts and feelings. For most, shoveling the driveway isn’t necessarily a joy — but adverse road conditions can be a serious hindrance to many people’s work and social routines. Disruptions in your regular routine can be enough to cause some mild SAD, especially if you’re predisposed to it. Triggers around the winter holidays in the northern hemisphere — such as separation from family members or grief — can also cause depressive symptoms, but this is different from SAD.
If you are one of the millions of individuals feeling the extra burden of SAD this winter, fear not: a range of therapeutic interventions are available. Most people, with the right diagnosis and treatment plan, can effectively manage even their worst symptoms.
Taking control of your health can be one of the best ways to alleviate seasonal depression. While there’s no way to fully prevent the illness, maintaining a healthy diet year-round — while taking special care to use moderation with holiday-season comfort foods — is a great place to start.
Regardless of your unsavory mood, or any looming adverse weather conditions, try not to isolate yourself, as loneliness can make the depression worse. When feeling doubtful or down, spending time with friends and family can be a welcome distraction. And, as desirable as a winter-long Netflix binge might sound, don’t forget to stay active. Getting regular physical exercise is one of the most effective ways to improve your mental health.⁴
In addition to garnering a sense of personal-health autonomy, the three most-commonly recommended interventions for SAD are:⁵
When it comes to healthy management of seasonal depression and finding relief from your SAD symptoms, the more self-interventions you can implement, the better off you will be. Making even small changes to your lifestyle and mentality can go a long way. Some things to consider include:⁵
Until your depressive mood has improved, it can also be a good idea to delay big life decisions, such as changing jobs, buying a home or vehicle, or getting married or divorced. Try to be patient, while maintaining focus on the positive elements of your life. As your depression responds to the treatments you have committed to — just as winter ultimately gives way to spring — your symptoms will begin to fade.⁵
Because the onset of seasonal depression is so predictable, those with a history of SAD will likely benefit from starting treatments or taking preventive measures before those shorter winter days begin to arrive. Often, seasonal depression starts in October and alleviates by April, so take steps in August or September (like purchasing a lightbox) to help your future self. Do what you can to lessen the biochemical disruptions of your internal clock and circadian rhythm. This will likely help you adjust more easily to any disturbances in your sleep, mood, or eating habits.
Each year, millions of Americans experience various combinations of symptoms related to SAD, and for many, this can be highly unnerving and uncomfortable. Seek guidance from a trained healthcare provider, psychiatrist, psychologist, or therapist if you’re wondering if this could be your situation. Keep in mind that SAD can be a symptom of other mental health conditions, such as bipolar disorder.
Lastly, if you feel your depression has become unmanageable or you are experiencing suicidal thoughts, be sure to immediately consult your healthcare provider, go to the nearest emergency room, or dial 988 to reach someone at the National Suicide Prevention Lifeline. Help is available, and you are not alone.
 National Alliance on Mental Illness. (2017, August). Major Depressive Disorder with a Seasonal Pattern. Retrieved January 15, 2023, from https://www.nami.org/About-Mental-Illness/Mental-Health-Conditions/Depression/Major-Depressive-Disorder-with-a-Seasonal-Pattern
 U.S. Department of Health and Human Services. (n.d.). Seasonal Affective Disorder. National Institute of Mental Health. Retrieved January 15, 2023, from https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder
 Seasonal Depression (seasonal affective disorder). Cleveland Clinic. (n.d.). Retrieved January 15, 2023, from https://my.clevelandclinic.org/health/diseases/9293-seasonal-depression
 American Psychological Association. (2022, November 28). Seasonal Affective Disorder: more than the winter blues. American Psychological Association. Retrieved January 15, 2023, from https://www.apa.org/topics/depression/seasonal-affective-disorder
 Seasonal Affective Disorder. Seasonal Affective Disorder | Johns Hopkins Medicine. (n.d.). Retrieved January 15, 2023, from https://www.hopkinsmedicine.org/health/conditions-and-diseases/seasonal-affective-disorder