Winter Doesn't Have to Destroy Your Mental Health: The Science of SAD and How to Fix It

Feeling down, foggy or unmotivated this winter? 

It’s not just you, or your willpower. 

Winter does something specific to your brain and body. 

It disrupts your circadian rhythm, tanks your neurotransmitters, and can even decrease blood flow to your brain by up to 30%. 

This is Seasonal Affective Disorder (SAD), and it's biology, not weakness.

The good news? I’m going to give you the science-backed tools and education to support your body and that actually work! 

First, what happens to our body in the winter? 

Your master clock lives in your eyes. It's called the suprachiasmatic nucleus (don’t worry, no test on this!) , and it controls almost everything: your sleep, your energy, your mood, your metabolism, and your immune function. When sunlight drops in winter, this clock can go a little out of sync. 

Here's what happens:

• Melatonin dysregulation - Melatonin is your sleep hormone. In winter, it stays elevated longer into the morning. You wake up exhausted because your brain is still in sleep mode. Your cortisol (your "get up and go" hormone) doesn't rise when it should, so you feel unmotivated and sluggish all day.

• Neurotransmitter crash - Serotonin (mood), dopamine (motivation and reward), and norepinephrine (focus and energy) all plummet when sunlight drops. This isn't a character flaw. It's neurochemistry.

• Reduced retinal sensitivity - In winter, the cells in your eyes that detect light become less sensitive. Your brain gets a faulty signal that it's darker than it actually is, which further disrupts your circadian rhythm.

• Brain blood can drop significantly - A rodent study showed that reduced light exposure literally decreases cerebral blood flow. Less oxygen to your brain = brain fog, inability to focus, scattered thoughts. This is in mice but very plausible it’s similar in humans.

• Neuroinflammation increases - Winter SAD is associated with increased pro-inflammatory cytokines in the brain and lower antioxidant defenses (like glutathione). Your brain is literally more inflamed.

• BDNF declines - Brain-derived neurotrophic factor (BDNF) is essential for neuroplasticity which is your brain's ability to form new connections and think clearly. It drops seasonally, making it harder to learn, adapt, and feel mentally sharp.

• Reduced brain glucose metabolism - Your brain uses less glucose efficiently in winter, contributing to brain fog and fatigue.

This cascade of changes is why SAD is real. It's not laziness. It's not depression you can think your way out of. It's biology.

Why it hits some people harder than others

Not everyone struggles equally in winter. Some people are more vulnerable to SAD because of how their body regulates neurotransmitters and hormones:

• The serotonin transporter (SERT) issue - Some people have a genetic or functional tendency to fail to down-regulate SERT (the protein that clears serotonin from synapses). This means less serotonin stays available in their brain, making them more vulnerable to the serotonin crash that winter causes.

• Dopamine sensitivity - People with lower dopaminergic tone are more affected by the motivation and reward circuit disruption that winter causes.

• HPA axis dysfunction - Some people's stress response system (hypothalamic-pituitary-adrenal axis) doesn't function optimally. Their cortisol doesn't rise adequately in the morning, making the winter energy crash worse.

• Melatonin sensitivity - Some people's bodies are more sensitive to the extended melatonin duration that winter causes, making them feel more tired and sluggish.

If you're reading this and thinking "that's me," it doesn't mean you're broken. It means you need to be more intentional about supporting your circadian rhythm and neurotransmitter health in winter. 

That's exactly what we're going to cover.

Image Source: https://magazine.medlineplus.gov/multimedia/falling-back-seasonal-affective-disorder

How to fix it: The Foundation 

Start here. Master these basics first before adding anything else. Most people feel dramatically better in 2-3 weeks.

1. GET SUNLIGHT

This is non-negotiable.

Even grey winter clouds are exponentially brighter than indoor light. Any sun is better than none. Aim for 30 minutes daily, ideally in the morning (6-9 AM is optimal).

Can't get outside? Even cloudy light counts. The brightness difference is massive: indoor light is typically 200-500 lux. Overcast winter daylight is still 5,000+ lux. Sunny days are 10,000+ lux.

What Sunlight Does:

• Regulates your circadian rhythm (fixes the melatonin/cortisol timing issue)

• Boosts serotonin and dopamine (improves mood and motivation)

• Increases cerebral blood flow by 30% (clears brain fog, improves focus)

• Triggers nitric oxide release from your skin (a vasodilator that improves circulation everywhere, lowering blood pressure and improving cardiovascular health)

• Triggers beta-endorphin production (the "sunlight high" that impacts mood and pain perception)

• Supports vitamin D synthesis

• Modulates your gut microbiome

• Enhances DNA repair and immune function

This is why people who avoid sun have mortality rates matching someone who smokes a pack a day. It's not just about vitamin D. Your body literally needs sunlight to function.

Action step: Tomorrow morning, get outside for 30 minutes. Even if it's cloudy. Even if it's cold. Your brain will thank you. 

2. OPTIMIZE VITAMIN D LEVELS

Aim for 50-80 ng/mL (this is NOT your standard western medicine range). 

Most people need 5,000 IU daily in winter to get there. Some need more depending on their baseline, location, and skin tone.

Get your levels tested. Don't guess. Supplement based on your levels because Vitamin D is fat-soluble, so too much can accumulate. 

3. REGULATE YOUR SLEEP/WAKE TIMES

Same bedtime. Same wake time. Even on weekends. (and no, you don’t have to be perfect for this to help!)

Your circadian rhythm is a rhythm. It needs consistency to function. Sleeping in on weekends might feel good, but it's like jet-lagging yourself every week. Your body can't adapt.

This single change fixes a lot of people's winter struggles. But it will NOT help if you are chronically sleep deprived. 

4. BLOCK BLUE LIGHT AT NIGHT

Blue light from screens and artificial lighting tells your brain it's daytime. In winter, when you're already struggling with melatonin timing, this makes it worse.

Wear dark red or amber blue-light blocking glasses 2-3 hours before bed. Orange glasses alone aren't enough, you need the darker, warmer spectrum.

Or simpler: put your phone and computer down 2-3 hours before bed and turn the TV off. Revolutionary, I know. Read a book. 

5. FOOD CUTOFF 3 HOURS BEFORE BED

Digestion raises your core body temperature. You need your core temperature to DROP to fall into deep sleep. Eating close to bedtime works against this.

Cut off food 3 hours before bed. This alone improves sleep quality significantly, especially combined with a cool room (63-67°F).

Still Struggling? Here’s the next layer

If you've nailed the five basics above and you're still struggling after 3-4 weeks, it's time to bring in targeted support. This is where supplements, bright light therapy, and personalized strategies come in.

Bright Light Therapy (The Most Powerful Intervention)

If basics aren't enough, bright light therapy is the most powerful tool we have for SAD.

10,000 lux white light lamp, 30 minutes daily, initiated early in the morning (6-9 AM).

This beats everything else. If you can only do one thing beyond sunlight, this is it.

The Supplement Stack

Quality matters. Choose third-party tested supplements from reputable brands. Better yet, work with a practitioner who specializes in supplemental health. Don't just try things on your own without guidance. The wrong supplement at the wrong dose can do more harm than good.

If you're working with me in ESN coaching, we'll personalize this based on your labs, medications, and individual needs. Here's the general framework:

• Vitamin D: Dosed by a provider (aim for blood levels at 50-80 ng/mL)

• Omega-3: 1,500-2,000 mg EPA/DHA combined daily (talk to your doctor first if you have AFib or a bleeding disorder)

• Magnesium: Supports sleep and mood (dose depends on form and individual needs)

• Saffron: 30 mg daily for at least 4-6 weeks. Research shows it helps depression but check for interactions.allergies. 

• Creatine: >5g daily for brain health (can split into doses to avoid GI upset)

• B vitamins and zinc: Covered by a high-quality multivitamin

  
  

Movement

Exercise cuts SAD symptoms by 50%. Aerobic exercise is more effective than resistance training for SAD specifically.

This is non-negotiable in winter. Move your body. Your brain depends on it.

Circadian Hygiene Optimization

Beyond the basics, you can dial in:

• Sleep in a very dark, cool room (63-67°F)

• No napping (even 20 minutes can disrupt your rhythm)

• Early time-restricted eating (eating in a narrower window improves deep sleep)

• Consistent meal timing

If you’re struggling…

It’s not weakness. It's not laziness. It's not depression you can think your way out of.

It's biology. Your brain needs light to function. Winter makes that harder.

But you have tools. Real, science-backed tools that work.

Start with the five foundations. Get sunlight, optimize vitamin D, regulate your sleep, block blue light, and cut off food before bed. Most people feel dramatically better in 2-3 weeks.

If you're still struggling, we have targeted support in 1:1 coaching that can get you feeling better!