The Wellness Report #11: Seasonal Affective Disorder: Real Condition or Winter Reaction?
Nutriburst Vitamins
December 5, 2025
What’s SAD?
SAD is a recognised mood disorder where symptoms appear during the darker months and lift when daylight returns. Researchers believe it stems from a few combined changes that happen in winter:
- Your body clock drifts when there’s not enough morning light.
- Your serotonin system shifts, affecting mood and motivation.
- Your melatonin rhythm changes, making you feel sleepy at the wrong times.
People with SAD experience these changes more intensely, leading to genuine depressive symptoms that follow a seasonal pattern.
What does it mean for you?
But for most people, winter low mood isn’t SAD at all. It’s something much more common — seasonal mood variation.
This isn’t an illness; it’s a natural biological response to darker days and disrupted routines.
Let’s explore what’s actually happening inside you:
1. Your body clock stops getting the signals it needs
Your brain relies on morning light to set your internal clock: it’s how your body knows when to wake up, feel alert, and wind down.
When winter takes that light away, your rhythm shifts. You may wake up slower, feel “out of sync,” or struggle with energy at the wrong times. That’s not you being unmotivated; it’s your circadian system trying to adapt without its main cue.
2. Your serotonin system slows down
Serotonin plays a huge role in your mood, motivation, and emotional steadiness. In winter, your brain naturally increases the transporters that clear serotonin away, leaving less available for you to use.
That’s why you might feel flatter, more sensitive, or less driven — even when nothing in your life has changed.
3. Your vitamin D levels drop sharply
From October to March in the UK, your body can’t make vitamin D from sunlight. Vitamin D isn’t just for bones — it supports how your brain regulates mood, stress, and even sleep.
When your levels fall, you feel it: your mood softens, your resilience dips, and your overall sense of wellbeing shifts.
4. Your routine tightens, and so does your resilience
Winter naturally shrinks your world — you move less, go outside less, see people less, and spend more time under artificial light.
Those small changes add up. They affect dopamine, increase inflammation, and make it harder for your brain to keep your mood and energy steady. It’s not a character flaw; it’s your environment influencing your biology.
So yes, SAD is real, and for some people it shows up as a genuine depressive pattern every winter.
But for most people, what you’re feeling isn’t SAD at all. It’s your biology responding to darker days: your body clock shifting, your serotonin changing, your vitamin D dropping, and your routines tightening without you noticing.
You don’t need a diagnosis to feel the season. Winter affects almost everyone — just not always in the same way.
Our Take
Effective winter wellness is about precision, not overhaul. We focus on small, meaningful supports — from daily habits to essentials your body struggles to maintain in darker months, like high-quality vitamin D or liposomal vitamin C — to help you stay regulated when sunlight can’t.