As the days grow shorter and the nights longer, many people notice a subtle, or sometimes dramatic, shift in mood, motivation and energy. For some, these winter blues deepen into a clinical pattern known as Seasonal Affective Disorder (SAD) — a recurrent depressive episode that begins in late fall and lifts by spring. Symptoms often include fatigue, oversleeping, increased appetite or weight gain, irritability and loss of interest in usual activities.¹

The exact cause of SAD remains complex, but several biological factors play a role. Reduced sunlight exposure disrupts the body’s circadian rhythm, our internal clock that regulates mood, sleep, and hormones. Fewer hours of sunlight also lead to decreased serotonin and dopamine activity, critical neurotransmitters responsible for positive mood and motivation. Finally reduced vitamin D production is linked to depressive symptoms and impaired serotonin synthesis.^2,3

Light therapy and nature. Simply spending time outdoors during daylight hours can be remarkably effective at reducing SAD. Brief walks in morning light, especially combined with gentle movement, can boost serotonin levels and energy balance. Studies show that regular outdoor exposure during winter can reduce depressive symptoms by up to 50%.⁴

For those unable to spend mornings outside, the most evidence-based natural treatment for SAD is light therapy, which uses a full-spectrum light box that mimics natural sunlight. Research shows that daily morning exposure to 10,000 lux of light for about 30 minutes can improve mood and regulate circadian rhythms within two weeks.5 Morning light is preferred, as it helps reset melatonin release and stabilizes sleep-wake cycles.

Nutrition and supplements. Diet also influences mood by providing the nutrients needed for neurotransmitter synthesis and inflammation regulation. A nutrient-dense diet rich in omega-3 fatty acids, vitamin D, magnesium, zinc and B vitamins support healthy brain and nervous system function.6 In particular, vitamin D3 supplementation (2,000–5,000 IU daily, depending on serum levels) may reduce depressive symptoms and improve energy.⁷

Herbal adaptogens such as Rhodiola rosea and St. John’s Wort have also demonstrated mood-stabilizing effects. Rhodiola enhances energy and resilience to stress, while St. John’s Wort supports serotonin metabolism, though professional supervision with a naturopathic doctor is recommended due to potential interactions with antidepressants and other medications.⁸

Movement, mindfulness and connection. Exercise is one of the most effective non-pharmacologic antidepressants. Moderate-intensity movement (brisk walking, yoga or strength training) at least three times weekly can improve mood and sleep quality.⁹ Mindfulness-based practices such as meditation, gratitude journaling or breathwork further support emotional resilience by reducing cortisol and improving parasympathetic tone.¹⁰

Finally, social connection is a vital yet often overlooked source of recovery. Spending time with loved ones, joining community activities, or seeking therapy helps buffer isolation and emotional withdrawal.^11,12 Cognitive-behavioral therapy (CBT) adapted explicitly for SAD has been shown to be as effective as light therapy for long-term outcomes.¹³

Bringing light back in. Addressing light exposure, nutrient balance, mindful movement, social connection and psychotherapy empower individuals to move through SAD with greater emotional stability, and create a foundation for well-being that helps the inner light return.

Dr. Salcido is a primary care naturopathic doctor at Live Well Clinic. Her focus is functional psychiatry utilizing naturopathic principles to work on root causes of mental health imbalance. She can be reached at (760) 771.5970 or www.livewellclinic.org.

References available upon request.