When the days get shorter and colder, you may start to feel a shift in your mood and energy. You might feel more tired, less social or not as cheerful as usual. For some people, these changes are more than just the “winter blues.” They may be signs of seasonal affective disorder [i], also known as SAD.
What is seasonal affective disorder?
Seasonal affective disorder is a type of depression that comes and goes on at certain times of the year. It usually begins in late fall, when there is less sunlight, and ends in the spring, when the days get longer.
People with SAD often feel sad, tired or have less energy. These feelings are stronger than just feeling “down” for a few days and can become profound and persistent over time.
While the exact cause of SAD isn’t fully known, experts believe it’s linked to less sunlight during the winter months. This lack of sunlight can disrupt:
- Your internal clock, which helps regulate your sleep-wake cycle.
- Your serotonin levels [ii], a chemical that helps you feel happy, may drop.
- Your melatonin levels [iii], a hormone that helps you sleep, may rise, making you feel tired.
- Your vitamin D levels [iv] can also drop, affecting your mood and energy.
All of these changes can make you feel sad, sleepy, or less interested in things you usually enjoy.
Roughly 5% of adults [v] in the U.S. experience seasonal affective disorder each year. It can affect anyone, but it is more common in adults than in children. As we age, people often start noticing symptoms more frequently. Changes in sleep, health or spending less time outside can make SAD symptoms more noticeable.
Where you live can make a difference [vi]. People in northern areas with shorter, darker winter days are more likely to experience seasonal affective disorder. For example, about 1% of people in Florida have SAD as compared to people in New York where the rate rises to around 5%. Further north, in states like New Hampshire, it can be as high as 10%. The farther you live from the equator, the less sunlight you get in winter — and the higher your risk for SAD.
Gender can also play a role. SAD is diagnosed more often in women. Changes in a woman’s estrogen levels can affect their moods and serotonin activity. Women are also more sensitive to changes or disruptions to the circadian rhythm [vii] — your body’s biological clock that tells you when to sleep, wake up and eat, among other functions. Changes in daylight and sleep patterns intensify these disruptions, which are central to SAD.
Moreover, having a personal or family history of anxiety, depression or bipolar disorder can increase one’s risk [viii] in developing SAD.
How do you know if you have seasonal affective disorder?
It can be hard to tell when you’re just feeling a bit down versus when it’s something more serious. If you or someone close to you notice changes in your mood, energy or sleep patterns with the seasons, it could be a sign of SAD.
The symptoms of SAD [ix] are similar to those of depression but happen during specific seasons. Symptoms can be emotional, behavioral or physical.
Emotional symptoms
- Feeling sad or down most of the day.
- Losing interest in hobbies or activities you used to enjoy.
- Feeling hopeless, guilty or worthless.
- Trouble focusing or making decisions.
Behavioral symptoms
- Sleeping more than usual.
- Eating more, especially craving carbohydrates such as bread or sweets.
- Avoiding friends or family.
- Having trouble getting things done and completing tasks.
Physical symptoms
- Feeling tired or low on energy.
- Gaining weight.
- Moving or speaking more slowly.
- Experiencing aches and pains that don’t seem to have a clear cause.
If such symptoms are ongoing or become worse with seasonal changes, we encourage you to talk with your doctor. They can help you find the treatment that’s right for you.
“Carol” a 39-year-old elementary school teacher, came to our office last February with symptoms of extreme fatigue. She felt as if she was “hibernating” and could not find the energy to go about her day. She reported lack of enthusiasm in teaching her students and becoming more irritable. As the days passed, she struggled getting through her day and gained over 15 pounds from overconsumption of what she called “comfort foods”. Upon further discussion, Carol recalled this pattern repeating itself over the past 2-3 winters. Carol was ultimately diagnosed with SAD.
SAD Diagnosis and Treatment
The good news is that SAD can be treated [x]. The best plan to combat SAD will depend on your symptoms and health history.
Light therapy
This treatment uses a special light box that mimics the brightness and intensity of sunlight. Sitting near it for about 30 to 60 minutes at the same time each day can help improve your mood and energy.
Talk therapy
Talking with a mental health professional [xi], such as a counselor or therapist, can help you manage stress and find ways to feel better. Cognitive behavioral therapy [xii] is particularly effective for SAD.
Medication
Your doctor may prescribe an antidepressant medicine to help balance mood-related chemicals in your brain.
Vitamin D
Low vitamin D can worsen symptoms of SAD. Ask your doctor if you should take supplemental vitamin D.
Lifestyle changes
You can also help manage SAD by making healthy changes to your daily routine:
- Spend time outdoors during daylight hours.
- Get regular exercise.
- Eat healthy foods, including fruits, vegetables and whole grains.
- Keep a regular sleep schedule and practice appropriate sleep hygiene.
- Stay in touch with family and friends.
If you’re not sure where to begin, talk to your doctor. They can help you find the proper support and create a treatment plan that fits your needs.
More than just the winter blues
While winter-pattern SAD is more common, summer-pattern SAD, also known as reverse SAD or “summer SAD”, is another a seasonal condition, that occurs in the late spring and summer months.
True to its moniker as reverse SAD, the symptoms of this condition are opposite winter-pattern SAD and include [xiii]:
- Insomnia
- Poor appetite and weight loss
- Increased anxiety
- Irritability
- In severe cases, violent behavior, or suicidal ideation
The exact cause of reverse SAD is unclear. A 2016 study [xiv] links rising temperatures to reduced emotional well-being. High pollen counts, and thus the rise of seasonal allergies, can also play a role in symptoms of summer SAD.
Social disruptions – including changes in routine and travel – can also bring on symptoms of reverse SAD.
And just as there are treatments for winter SAD, there are things you can do to help combat summer SAD [xv], including finding ways to stay cool and comfortable during the higher temperatures. Prioritizing sleep is also key.
What can families do to help?
Whether your loved one has winter or summer SAD, here are ways to support them:
- Encourage them to get outside or sit by a sunny window.
- Help them maintain a healthy daily routine.
- Plan visits or fun outdoor activities together.
- Remind them that it’s okay to ask for help.
- Offer to accompany them to see their doctor.
Even small gestures like sharing a meal or spending time together can make a big difference in people experiencing symptoms of SAD.
When to see your doctor
Feeling down sometimes is normal, but ongoing sadness or low energy that lasts for weeks and affects your daily life may be a sign of SAD. You don’t have to wait until it’s unbearable to get help.
Your health care provider can help you determine if it’s seasonal affective disorder or something else responsible for the notable changes. They will guide you to the proper treatment and resources.
References
[i] Seasonal Affective Disorder. National Institute of Mental Health (2023). https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder
[ii] Effect of sunlight and season on serotonin turnover in the brain. National Library of Medicine, National Center for Biotechnology Information (2002). https://pubmed.ncbi.nln.nih.gov/12480364
[iii] Melatonin and Seasonal Affective Disorder: How Is It Linked? HealthMatch (2022). https://healthmatch.io/seasonal-affective-disorder/melatonin-seasonal-affective-disorder
[iv] Vitamin D Levels in Children During Winter and the Relationship Between Sunscreen and Sun Protection Behaviors. National Library of Medicine, National Center for Biotechnology Information (2023). https://pmc.ncbi.nlm.nih.gov/articles/PMC10412075/
[v] Seasonal Affective Disorder (SAD). American Psychiatric Association (2024). https://www.psychiatry.org/patients-families/seasonal-affective-disorder
[vi] Winter Depression Research Clinic: What is Seasonal Affective Disorder (“SAD”)? Yale School of Medicine. https://medicine.yale.edu/psychiatry/research/clinics-and-programs/winter-depression/
[vii] Why Seasonal Affective Disorder (SAD) Affects Women at Higher Rates. Happy Hormone Cottage. (2021). https://happyhormonecottage.com/blog/why-seasonal-affective-disorder-sad-affects-women-at-higher-rates/
[viii] Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. National Library of Medicine, National Center for Biotechnology Information (2015). https://pmc.ncbi.nlm.nih.gov/articles/PMC4673349/
[x] Seasonal Affective Disorder: Common Questions and Answers. National Library of Medicine, National Center for Biotechnology Information (2020). https://pubmed.ncbi.nlm.nih.gov/33252911/
[xi] Specialists for Health. WellMed. https://www.wellmedhealthcare.com/patients/your-specialists/
[xii] Cognitive behavioral therapy. Mayo Clinic (2025). https://www.mayoclinic.org/tests-procedures/cognitive-behavioral-therapy/about/pac-20384610
[xiii] Seasonal affective disorder (SAD). Mayo Clinic (2021). https://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/symptoms-causes/syc-20364651
[xiv] Increasing ambient temperature reduces emotional well-being. ScienceDirect (2016). https://www.sciencedirect.com/science/article/abs/pii/S001393511630281X
[xv] Understanding and Managing Summer SAD: Examining the causes and symptoms of summer-pattern seasonal affective disorder. Psychology Today (2024). https://www.psychologytoday.com/us/blog/a-deeper-wellness/202405/understanding-and-managing-summer-sad
