Many people describe this as the most wonderful time of the year, a season filled with festive lights, gatherings, and celebration. But what if you’re not feeling the joy? You might be asking yourself, “The holidays are here, so why don’t I feel happy?” If you find your mood and energy
levels dropping as the days get shorter, you’re not alone. This common experience is often dismissed as the “winter blues,” but for many, it’s a recognized medical condition known as Seasonal Affective Disorder, or SAD.
At TWA Psychiatry, we believe in looking at the entire picture of your health, including the patterns that often emerge with the change of seasons. We’ve seen how the shift in daylight can profoundly impact mental well-being, and the growing body of research reveals this goes well beyond anecdote. In this post, we’ll explore the mechanisms behind SAD, why it happens, and discuss evidence-based approaches—including syncing your circadian rhythm and using light therapy—to help you stay balanced and supported through the darker months.
What Is Seasonal Affective Disorder (SAD)?
Seasonal Affective Disorder is a form of depression that follows a seasonal pattern, most commonly beginning in the fall and continuing through the winter months. While it is less common, SAD can affect some individuals in the spring or summer as well. Characteristic symptoms include:
● Feeling depressed most of the day, nearly every day
● Losing interest in activities you once enjoyed
● Low energy and feeling sluggish or agitated
● Oversleeping and changes in sleep patterns
● Changes in appetite, particularly craving carbohydrate-rich foods
● Difficulty concentrating
● Feelings of hopelessness or worthlessness
So where does this feeling come from, especially at “the most wonderful time of the year”? The answer is rooted in our biology—specifically, in how our bodies respond to changing light levels.
The Science Behind the Winter Blues
Our bodies are remarkable timekeepers. Every cell carries its own molecular clock, but all these internal clocks rely on cues from the environment to keep in sync—a process coordinated by what’s known as the circadian rhythm. Your circadian rhythm is a roughly 24-hour cycle
regulating sleep, hormones, metabolism, and even mood. The master clock resides in the brain, in an area called the suprachiasmatic nucleus, which receives signals from light-sensitive cells in your eyes.
As the days grow shorter, the amount and timing of natural sunlight that reaches your eyes changes dramatically. This subtle shift is more powerful than you might think:
● Disrupted Melatonin Production: Melatonin, the hormone that helps regulate sleep, is produced in darkness. During winter, as you’re exposed to less daylight, your body may produce melatonin earlier, or in greater quantities, making you feel sleepy or sluggish during the day.
● Serotonin and Mood: Sunlight also plays a vital role in regulating serotonin—a neurotransmitter closely linked to mood, appetite, and energy. A drop in sunlight can lead to lower serotonin levels, which may contribute to feelings of depression. Brain imaging studies show that people with SAD often have higher levels of a protein that removes serotonin from the brain in winter, limiting its mood-boosting effects.
● Circadian Misalignment: The master clock relies on morning sunlight as its cue to reset for the day, but late sunrises and weaker light in winter can blur these signals. Eating at irregular hours or getting less physical activity—common in winter—can further desynchronize the clocks in your body, compounding the effects on mood, sleep, and metabolic health.
These disruptions form the core of why many people experience SAD. But understanding this mechanism empowers us with strategies to manage the impact.
Finding Your Rhythm: Evidence-Based Treatments
There’s good news: the science of circadian rhythms and brain chemistry unlocks practical, proven ways to ease the symptoms of SAD.
Light Therapy (Phototherapy): Resetting Your Internal Clock
One of the most effective, well-studied interventions for SAD is light therapy. Using a special light box that emits 10,000 lux of bright, full-spectrum light—mimicking the sun’s rays—early in the day can help resynchronize your circadian rhythm, boost serotonin, and reduce melatonin production at the right times.
● How to Use Light Therapy: Sit near the light box for 20-30 minutes every morning, ideally soon after waking up. Placement matters—the light should reach your eyes, but you don’t have to look directly at it.
● Why It Works: The bright light sends strong “morning” signals to the master clock in your brain, helping reset your daily cycle. Decades of research—even in places as far north as Sweden—show that light therapy can meaningfully improve mood and energy
during dark months and is now recommended as a first-line treatment by many mental health professionals.
● Public Adaptations: Some communities have even installed public light therapy boxes in bus stations and public spaces to help residents cope with the lack of winter sunlight.
Diet and Movement: Supporting Your Body’s Clock
Your body’s clocks aren’t just set by light; what and when you eat, and how you move, play important roles, too.
● Time Your Meals: Studies show that eating most of your food during daylight hours—ideally within a 10-12 hour window—can help align your digestive system’s clocks with your brain, improving energy and mood.
● Complex Carbohydrates and Omega-3s: Reach for whole grains instead of sugar-heavy snacks. Omega-3 fatty acids, found in fish, flaxseed, and walnuts, support brain and mood health.
● Vitamin D: Sunlight prompts your skin to produce vitamin D, which supports mood and immune function. As levels drop in winter, talk to your provider about getting your vitamin D checked and supplementing if needed.
● Regular Physical Activity: Moving your body boosts serotonin and helps regulate sleep. Aim for at least 30 minutes of moderate activity most days, and try to exercise outdoors in daylight when possible.
Anchor Your Routine: The Power of Consistency
Your circadian rhythm thrives on predictability. Keep a regular sleep schedule—going to bed and waking up at the same time each day, even on weekends. Get as much natural light as you can in the morning. Consider minimizing light exposure, big meals, and vigorous exercise in the hour or two before bed, to encourage restful sleep.
Tracking your habits using tools or apps designed for circadian health may help you stay consistent, which research shows can make a real difference in mood and energy.
Additional Support
If you feel like you may be needing an additional pillar of support this season, there are other resources and treatment options available.
● Find a therapist: Have someone in your corner that can offer an empathetic ear during this time of family and togetherness. This can be an especially challenging time for those undergoing stress, anxiety, or dealing with loss.
● TMS therapy: Find a treatment that can help you build back resilience during a time of year when not just the bitter cold, but feelings of isolation and depression start inviting themselves in. If this is a hectic time of year for you, the ONE-D protocol (that only takes one day!) may be well-suited to your needs. You can find out more about this option by
reading our previous blog post: (LINK –
https://twapsychiatry.com/one-d-tms-depression-treatment-compressed-into-a-single-day /)
There’s Hope During The Holidays
Living with Seasonal Affective Disorder can be especially tough when everyone around you seems to be celebrating. Remember: SAD is a treatable, real medical condition rooted in the interplay between light, biology, and mood. By understanding how your circadian rhythm, melatonin, and serotonin interact, and by using evidence-based treatments like light therapy and structured routines, you can reclaim more energy and optimism this season.
If you’re needing help getting started, please visit our “contact us” page above to get started.