Every December, without fail, a familiar pattern shows up in my life - and in the lives of so many women I speak to. We step into holiday season hoping for rest, connection, and joy… and instead we often get a strange mix of exhaustion, emotional sensitivity, disrupted routines, and a body that feels somehow “off.”

It’s not that anything is wrong with us. It’s that the holidays collide directly with the biology of the menstrual cycle - and with the brain systems responsible for how we process stress, pain, and emotion.

And when these systems are already sensitive (because of PMS, PMDD, period pain, endometriosis, or just normal hormonal shifts), December can feel like the perfect storm.

I wanted to write about this because so many women enter the holidays thinking they’re “just stressed,” when the truth is much deeper, more neurological, and far more predictable.

This is the holiday hormone crash - through the lens of the brain.

The emotional pressure of December hits a brain that’s already working harder than people realize

One thing I’ve learned-both through the science and through my own experience is that December doesn’t have to line up perfectly with a specific phase (yes, I’m looking at you, luteal) of the menstrual cycle to feel overwhelming.

Across the cycle, there are moments when the brain becomes more sensitive to stress, social load, and emotional friction. What the research shows happens during the luteal phase:

• The prefrontal cortex, responsible for emotional regulation, becomes less responsive.
• Alpha wave asymmetry, linked to mood instability, increases.
• GABA, the brain’s calming neurotransmitter, becomes dysregulated as progesterone rises then falls, contributing to emotional sensitivity (Rode (2010)).

These neurological changes happen on repeat, every month, regardless of the calendar.

So even if you’re nowhere near your luteal phase in December, the external demands of the season-family dynamics, disrupted routines, late nights, social expectations, travel, sensory overload-place stress on brain systems that are already cycling through predictable peaks and dips in sensitivity.

That’s the real collision: a month that asks for constant emotional output meeting a brain that is designed for rhythmic fluctuation, not unbroken performance. It’s not obvious or a character flaw - it’s physiology meeting your modern calendar.

Holiday stress amplifies pain - especially menstrual and endometriosis pain

Pain is shaped far less by the body and far more by the brain than most people realize. Neuroimaging shows that women with period pain experience heightened pain sensitivity across their whole cycle, not only during their period (Iacovides (2015)).

During December, several factors collide:

• disrupted sleep
• higher stress levels
• increased inflammation
• inconsistent eating patterns
• alcohol intake
• reduced movement

All of these are known to lower the brain’s pain threshold. Meaning: the nervous system becomes hypersensitive, and holiday disruptions intensify pain.

If your symptoms spike this time of year, you’re not imagining it - your central nervous system is responding exactly as the evidence predicts.

For women with endometriosis, this effect becomes even more layered - not just because of pain, but because of how the brain adapts to that pain over time.

Research shows:

• widespread central sensitization, where the nervous system amplifies pain signals (Quinta-Marques (2023))
• altered connectivity in networks that process pain and emotion
• changes in neurotransmission in regions like the insula, amygdala, and hippocampus that regulate both pain and mood (McNamara (2021))

This means the brain begins to operate from a more reactive baseline - the volume on pain is already turned up. Add holiday stress, disrupted routines, extra sensory load, and irregular sleep, and it’s not surprising that symptoms intensify.

Why your brain hates the holidays more than you think

The brain thrives on rhythm, predictability, and stable inputs:

• The menstrual cycle is a rhythm.
• Daily routines are rhythms.
• The nervous system uses these patterns to regulate itself.

December is the annual ritual of breaking all of them at once.

If your symptoms - emotional, cognitive, or physical - feel worse this time of year, it doesn’t mean you’re not coping. It means your brain is trying to adapt to an environment it didn’t evolve for.

This is why we built Samphire: a neuroscience-based cycle and symptom diary that gives you a sense of your rhythm even when your external world is falling out of routine.

Brain-based support is the missing piece - and where Nettle™ and Lutea™ comes in

At Samphire Neuroscience, we’ve spent years studying how the brain shapes menstrual pain, mood, and sensitivity. The clearest conclusion from the research is this: supporting the brain directly changes the experience of the menstrual cycle.

That’s exactly what Nettle™ does.

Our clinical research shows:

• 53% reduction in menstrual pain in one cycle in a randomized controlled trial (the gold standard)
• 67% reduction in low mood symptoms in one cycle in a randomized controlled trial
• improvements in mood, irritability, and emotional regulation
• zero severe side effects
• Hormone and drug free - can use whilst still on antidepressants, birth control, painkillers, or any other medication

By targeting the dorsolateral prefrontal cortex (DLPFC) and motor cortex, Nettle™ and Lutea™ help stabilize the very systems most vulnerable during holiday stress.

If December reliably derails you, there is a brain-based way to feel different.

This holiday season, honor your brain - not just your calendar

If you’ve ever walked into Christmas with the best intentions only to walk out overwhelmed, low, or in pain, you’re not alone - and you’re not doing anything wrong.

Holiday expectations rise at the exact moment many women are neurologically more sensitive.

Supporting the brain - through understanding, rhythm, and neuromodulation - is one of the most effective ways to feel more steady.