Why do I feel worse in winter months?
Winter can trigger mood changes, fatigue, and physical symptoms due to reduced sunlight exposure, vitamin D deficiency, disrupted circadian rhythms, and lifestyle factors. Understanding these causes and monitoring key biomarkers like vitamin D, cortisol, and thyroid hormones can help you develop effective strategies to feel better during colder months.
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The Science Behind Winter Blues
If you notice your energy plummeting and mood darkening as the days grow shorter, you're not alone. Research shows that up to 20% of people experience some form of winter-related mood changes, ranging from mild winter blues to clinically diagnosed Seasonal Affective Disorder (SAD). This seasonal shift isn't just in your head—it's a complex interplay of biological, environmental, and lifestyle factors that can significantly impact your physical and mental wellbeing.
The winter months bring dramatic changes to our environment: shorter days, less sunlight, colder temperatures, and often more time spent indoors. These changes trigger a cascade of physiological responses in your body, affecting everything from hormone production to neurotransmitter balance. Understanding these mechanisms is the first step toward feeling better during the darker months.
Key Biological Factors That Change in Winter
Vitamin D Deficiency
Vitamin D, often called the sunshine vitamin, plays a crucial role in mood regulation, immune function, and overall health. During winter, reduced sun exposure can cause vitamin D levels to plummet. Studies show that vitamin D deficiency affects up to 42% of Americans, with rates significantly higher during winter months. Low vitamin D has been linked to depression, fatigue, muscle weakness, and increased susceptibility to infections.
Winter Hormonal Changes and Their Effects
| Hormone | Winter Change | Symptoms | Optimal Range | |
|---|---|---|---|---|
| Melatonin | Melatonin | Increased production | Daytime drowsiness, oversleeping | 0.5-5 pg/mL (nighttime) |
| Serotonin | Serotonin | Decreased levels | Low mood, anxiety, carb cravings | 101-283 ng/mL |
| Cortisol | Cortisol | Disrupted rhythm | Fatigue, stress sensitivity | 6-23 mcg/dL (morning) |
| Vitamin D | Vitamin D | Significant decrease | Depression, fatigue, weak immunity | 40-60 ng/mL |
| TSH | TSH | May increase | Cold intolerance, weight gain | 0.4-2.5 mIU/L |
These hormonal changes can compound each other, creating a cascade of winter symptoms.
Your skin produces vitamin D when exposed to UVB radiation from sunlight, but this process becomes nearly impossible in many regions during winter. Above 37 degrees latitude (roughly north of San Francisco), the sun's angle is too low from November through February to trigger adequate vitamin D synthesis, even on sunny days. If you're experiencing persistent fatigue or mood changes during winter, getting your vitamin D levels tested can provide valuable insights into whether supplementation might help.
Disrupted Circadian Rhythms
Your circadian rhythm, or internal body clock, relies heavily on light exposure to regulate sleep-wake cycles, hormone production, and metabolism. Winter's reduced daylight hours can throw this delicate system off balance. The lack of morning light exposure can delay your circadian phase, making it harder to wake up and feel alert in the morning, while early darkness can trigger premature melatonin release, leaving you feeling tired by late afternoon.
This disruption affects more than just sleep. Your circadian rhythm influences cortisol release, body temperature fluctuations, and even digestive processes. When these rhythms are misaligned, you might experience symptoms like daytime fatigue, difficulty concentrating, changes in appetite, and mood disturbances. Understanding your cortisol patterns throughout the day can help identify circadian disruptions.
Hormonal Changes
Winter triggers several hormonal shifts that can affect your mood and energy levels. Melatonin production increases with longer periods of darkness, potentially leading to oversleeping and daytime drowsiness. Meanwhile, serotonin levels, which are influenced by sunlight exposure, tend to decrease during winter months. This neurotransmitter plays a vital role in mood regulation, and lower levels are associated with depression and anxiety.
Thyroid function can also be affected by seasonal changes. Some people experience subclinical hypothyroidism during winter, with slightly elevated TSH levels that can contribute to fatigue, weight gain, and cold intolerance. Additionally, cortisol patterns may become dysregulated, with some individuals showing flattened cortisol curves that correlate with increased fatigue and reduced stress resilience. The following table outlines how these hormonal changes manifest:
Common Winter Symptoms and Their Causes
Winter-related symptoms can vary widely in severity and presentation. While some people experience mild changes in energy and mood, others face more significant challenges that interfere with daily functioning. Understanding the full spectrum of potential symptoms can help you identify patterns in your own experience and determine when to seek additional support.
Physical Symptoms
- Persistent fatigue despite adequate sleep
- Increased appetite, especially for carbohydrates
- Weight gain (average 1-2 pounds for mild cases, up to 10+ pounds for SAD)
- Joint and muscle aches
- Weakened immune response and frequent colds
- Headaches and migraines
- Digestive issues and bloating
Mental and Emotional Symptoms
- Persistent low mood or sadness
- Loss of interest in activities you normally enjoy
- Difficulty concentrating or brain fog
- Increased anxiety or irritability
- Social withdrawal and isolation
- Feelings of hopelessness or worthlessness
- Changes in libido
These symptoms often begin gradually in fall and peak during January and February when daylight is most limited. The severity can range from mild winter blues that don't significantly impair functioning to Seasonal Affective Disorder, which affects 5% of adults and can severely impact quality of life. Understanding where you fall on this spectrum can help guide appropriate interventions.
Lifestyle Factors That Worsen Winter Symptoms
While biological factors create vulnerability to winter-related symptoms, lifestyle choices can either amplify or mitigate these effects. Many common winter behaviors, though seemingly comforting, can actually worsen mood and energy problems.
Reduced Physical Activity
Cold weather and icy conditions often lead to decreased outdoor activity and exercise. This reduction in movement has cascading effects: decreased endorphin production, reduced vitamin D synthesis from outdoor exposure, weight gain, and decreased cardiovascular fitness. Regular exercise has been shown to be as effective as light therapy for treating mild to moderate seasonal depression, yet winter is when most people move the least.
Dietary Changes
Winter comfort foods tend to be high in refined carbohydrates and sugar, which can cause blood sugar spikes and crashes that worsen mood instability and fatigue. The biological craving for carbohydrates during winter is linked to serotonin production, as carbs temporarily boost serotonin levels. However, this creates a cycle of energy crashes and cravings that can lead to weight gain and metabolic dysfunction.
Additionally, reduced access to fresh produce in winter can lead to lower intake of essential nutrients like folate, magnesium, and omega-3 fatty acids, all of which play crucial roles in mood regulation and energy production. If you're curious about how your diet might be affecting your metabolic health during winter months, comprehensive biomarker testing can reveal important patterns.
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Evidence-Based Strategies to Feel Better in Winter
Fortunately, numerous evidence-based interventions can help counteract winter's negative effects on mood and energy. The key is finding the right combination of strategies that work for your specific situation and symptoms.
Light Therapy
Bright light therapy is one of the most effective treatments for winter-related mood issues. Exposure to 10,000 lux of bright light for 20-30 minutes each morning can help reset circadian rhythms and boost mood. Studies show that light therapy can be effective within 1-2 weeks for many people. Position the light box at eye level, about 16-24 inches from your face, and use it while eating breakfast, reading, or working on your computer.
Optimize Vitamin D Levels
Most experts recommend maintaining vitamin D levels between 30-50 ng/mL, though some research suggests optimal levels may be higher, around 40-60 ng/mL. During winter, achieving these levels typically requires supplementation. The Endocrine Society recommends 1,500-2,000 IU daily for adults, though individual needs vary based on baseline levels, body weight, and absorption. Taking vitamin D with a fat-containing meal improves absorption by up to 50%.
Strategic Exercise
Maintaining regular exercise during winter is crucial for mood and energy. Aim for at least 150 minutes of moderate-intensity exercise weekly, with a combination of cardio and strength training. Outdoor exercise during daylight hours provides the dual benefit of movement and light exposure. If outdoor exercise isn't feasible, consider joining a gym, following online workout videos, or investing in home exercise equipment.
Monitoring Your Winter Health Through Biomarkers
While symptoms provide important clues about your winter wellness, biomarker testing offers objective data about what's happening inside your body. Key markers to monitor during winter months include vitamin D, thyroid hormones (TSH, Free T3, Free T4), cortisol patterns, inflammatory markers like hs-CRP, and metabolic markers including fasting glucose and HbA1c.
Regular testing can help you identify deficiencies before they become symptomatic, track the effectiveness of interventions like supplementation, and distinguish between winter blues and underlying health conditions. Many people discover that what they attributed to seasonal changes actually stems from correctable nutritional deficiencies or hormonal imbalances.
If you have existing blood test results, you can get a comprehensive analysis of your biomarkers using SiPhox Health's free upload service. This service provides personalized insights and recommendations based on your unique health data, helping you understand how your biomarkers might be contributing to winter symptoms.
When Winter Symptoms Signal Something More Serious
While some degree of winter sluggishness is common, certain symptoms warrant professional medical attention. Seek help if you experience persistent depression lasting more than two weeks, thoughts of self-harm or suicide, significant weight changes (gain or loss of more than 5% body weight), inability to function at work or maintain relationships, or severe fatigue that doesn't improve with rest.
These symptoms might indicate Seasonal Affective Disorder, clinical depression, thyroid disorders, or other medical conditions that require professional treatment. A healthcare provider can perform comprehensive testing, rule out underlying conditions, and recommend appropriate treatments, which might include psychotherapy, medication, or referral to specialists. The comparison table below outlines when symptoms typically warrant professional evaluation:
Creating Your Winter Wellness Plan
Developing a personalized winter wellness strategy involves understanding your unique vulnerabilities and implementing targeted interventions before symptoms become severe. Start by tracking your symptoms and identifying patterns from previous winters. Note when symptoms typically begin, peak, and resolve, as well as which interventions have helped in the past.
Consider creating a winter wellness toolkit that includes a light therapy box for morning use, vitamin D supplements dosed according to your tested levels, an exercise plan that accounts for weather limitations, meal prep strategies focused on nutrient-dense foods, stress management techniques like meditation or yoga, and a sleep hygiene routine that supports circadian rhythm regulation.
Remember that winter wellness isn't about eliminating all seasonal changes but rather supporting your body's adaptation to environmental shifts. By understanding the biological basis of winter symptoms and implementing evidence-based strategies, you can maintain better mood, energy, and overall health throughout the colder months. Regular monitoring of key biomarkers can provide valuable feedback on your progress and help you fine-tune your approach for optimal winter wellness.
References
- Melrose, S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, 178564.[Link][PubMed][DOI]
- Holick, M. F. (2017). The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Reviews in Endocrine and Metabolic Disorders, 18(2), 153-165.[PubMed][DOI]
- Pjrek, E., Friedrich, M. E., Cambioli, L., et al. (2020). The Efficacy of Light Therapy in the Treatment of Seasonal Affective Disorder: A Meta-Analysis of Randomized Controlled Trials. Psychotherapy and Psychosomatics, 89(1), 17-24.[PubMed][DOI]
- Wirz-Justice, A., Skene, D. J., & Münch, M. (2021). The relevance of daylight for humans. Biochemical Pharmacology, 191, 114304.[PubMed][DOI]
- Kurlansik, S. L., & Ibay, A. D. (2012). Seasonal affective disorder. American Family Physician, 86(11), 1037-1041.[Link][PubMed]
- Anglin, R. E., Samaan, Z., Walter, S. D., & McDonald, S. D. (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry, 202(2), 100-107.[PubMed][DOI]
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