You're in your late 30s or 40s. You've always been capable, resilient, a high-functioning person. And then, almost without warning, things start to unravel.

You're exhausted but you can't sleep. Your anxiety has ramped up in ways that feel disproportionate to your life. Your heart races for no reason. Digestion that was never a problem is suddenly all over the place. Brain fog has moved in like an unwelcome houseguest. And your tolerance (for noise, for stress, for everything) has dropped through the floor.

Sound familiar? This is perimenopause. And while hormones are absolutely part of the picture, what doesn't get talked about nearly enough is the nervous system's central role in why this transition is so destabilising for so many women.

What Is Perimenopause, Exactly?

Perimenopause is the transition period leading up to menopause — typically beginning in the early-to-mid 40s, though it can start as early as the mid-30s. It is defined by fluctuating (and eventually declining) levels of oestrogen and progesterone, and it ends 12 months after a woman's final menstrual period.

It can last anywhere from 2 to 12 years.

During this time, the hormonal fluctuations can be dramatic and erratic - often more so than they were even during puberty. And these hormonal shifts have profound effects on the nervous system.

Oestrogen and the Nervous System: A Love Story (That's Ending)

Oestrogen is not just a reproductive hormone. It is deeply neuroprotective — meaning it actively supports the health and function of the brain and nervous system.

Oestrogen:

Modulates neurotransmitter activity, including serotonin, dopamine, and GABA - the calming neurotransmitter that helps regulate anxiety and sleep
Supports the HPA axis (the hypothalamic-pituitary-adrenal axis), which governs the stress response
Protects the myelin sheath — the protective coating around nerve fibres that allows for efficient nerve signalling
Influences vagal tone — higher oestrogen levels are associated with better parasympathetic activity and heart rate variability
Regulates body temperature through its effects on the hypothalamus (explaining hot flushes)
Supports hippocampal function — which is why memory and cognitive clarity are often affected during perimenopause

When oestrogen begins to decline and fluctuate, all of these neurological functions are destabilised. The nervous system, quite literally, loses a key regulator.

Why the vagus nerve is so central to the perimenopause experience

The vagus nerve (the primary nerve of the parasympathetic nervous system) is your body's most powerful brake pedal. It pulls you out of stress activation and into rest, recovery, and regulation.

In perimenopause, vagal tone tends to decline. This happens for several interconnected reasons:

Falling oestrogen reduces parasympathetic tone — the nervous system becomes more sympathetically dominant (more "switched on," more reactive)
Sleep disruption — one of the most common and distressing symptoms of perimenopause — directly impairs vagal tone recovery (which primarily occurs during deep sleep)
Gut changes — oestrogen influences the gut microbiome, and as it declines, gut dysbiosis can worsen, reducing the vagal signalling that travels from gut to brain
Accumulated stress load — many women entering perimenopause are carrying significant allostatic load: years of caregiving, work demands, sleep deprivation, and emotional labour. The nervous system enters this transition already depleted.

The result is a nervous system that is less able to regulate itself and more prone to anxiety, overwhelm, heart palpitations, digestive upset, and what many women describe as a pervasive sense that their "internal thermostat" is broken.

The symptoms that are actually nervous system symptoms

Many classic perimenopause symptoms that are attributed solely to hormones are, at their core, nervous system symptoms:

Anxiety and panic The decline in GABA activity (driven by falling progesterone and oestrogen) reduces the brain's natural "calm" signalling. Combined with reduced vagal tone, the nervous system becomes hypervigilant — stuck in a low-grade fight-or-flight state.

Heart palpitations The heart is one of the most heavily vagally innervated organs in the body. Reduced vagal tone means less parasympathetic regulation of heart rate, resulting in palpitations, racing heart, and a heightened awareness of the heartbeat. (Always worth having these assessed medically, but they are extremely common in perimenopause and often neurological in origin.)

Sleep disruption The hypothalamus (which regulates both the sleep-wake cycle and body temperature) is heavily influenced by oestrogen. As oestrogen fluctuates, the hypothalamus becomes dysregulated, disrupting circadian rhythm and sleep architecture. Night sweats further fragment sleep, creating a vicious cycle of nervous system depletion.

Digestive changes The gut is sometimes called the "second brain," and for good reason — it contains over 100 million neurons and communicates directly with the brain via the vagus nerve. Oestrogen influences gut motility, microbiome composition, and intestinal permeability. As it declines, many women experience new or worsening IBS, bloating, constipation, or reflux — all signs of a gut-brain axis under stress.

Brain fog and memory changes Oestrogen supports the production of acetylcholine — a neurotransmitter critical for memory and concentration. It also influences blood flow to the brain. The brain fog of perimenopause is real, neurological, and not a sign of cognitive decline but it is a sign the nervous system needs support.

Temperature dysregulation Hot flushes and night sweats are the result of hypothalamic dysregulation — the brain's thermostat misfiring due to hormonal changes. Research has found that women with lower vagal tone experience more severe and frequent vasomotor symptoms, reinforcing the nervous system's central role.

Why this transition is harder for some women than others

Not all women experience perimenopause the same way. Some sail through with minimal disruption. Others are floored by it. What makes the difference?

Nervous system resilience.

Women who enter perimenopause with a more regulated, resilient nervous system - higher vagal tone, lower allostatic load, better sleep, robust gut health - tend to navigate the hormonal fluctuations more smoothly. Their nervous system has more capacity to absorb the changes.

Women who enter this transition already dysregulated (due to chronic stress, trauma history, burnout, poor sleep, or cumulative health challenges) often find that perimenopause tips them into a state of genuine nervous system crisis. The hormonal changes are the final straw for a system that was already struggling to cope.

This is not weakness. It is physiology. And it points directly to the solution.

Supporting the nervous system through perimenopause

Addressing the nervous system directly (rather than waiting for hormones to stabilise) can make a significant difference to how you experience this transition.

Vagal tone support Practices that directly stimulate the vagus nerve can help shift the nervous system toward greater parasympathetic activity. These include:

Slow, diaphragmatic breathing (extended exhale)
Humming, singing, or chanting
Cold water exposure (even splashing cold water on the face)
Gentle, rhythmic movement - walking, swimming, yoga
Social connection and laughter (yes, genuinely, these activate the ventral vagal system)

Chiropractic care and nervous system assessment The upper cervical spine, sacral spine, and the neural structures that run through them all play a role in autonomic nervous system function. Chiropractic assessment and care during perimenopause (particularly through the lens of vagal tone and autonomic balance) can support the nervous system's capacity to regulate itself. Applied kinesiology can also be valuable in identifying where the nervous system is under stress and what it needs to restore function.

Gut health Given the bidirectional relationship between the gut and the nervous system, supporting microbiome health during perimenopause is not optional, it's essential. Fermented foods, prebiotic fibre, and addressing any underlying dysbiosis can have meaningful upstream effects on mood, anxiety, and cognitive function.

Sleep prioritisation Sleep is when the nervous system recovers. If sleep is severely disrupted (and in perimenopause, it often is), addressing this (whether through sleep hygiene, vagal tone support, hormone therapy, or a combination) needs to be a priority, not an afterthought.

Reducing allostatic load This is the hardest one, because it often requires saying no to things that feel important. But the nervous system cannot regulate itself if it is chronically overloaded. Reducing the demands placed on the system, even incrementally, creates space for recovery.

Considering hormone therapy For many women, HRT (hormone replacement therapy) or bioidentical hormones are an important part of the picture — particularly for the neurological symptoms described above. This is a conversation worth having with a well-informed GP or gynaecologist. Nervous system support and hormonal support are not mutually exclusive — they work best together.

You are not falling apart

The women who come to me in perimenopause are often bewildered and frightened by how different they feel. They've been high-functioning, capable people and suddenly their body and mind feel unreliable.

What I want them to understand and what I want you to understand is that this is not a personal failing. It is a physiological transition that genuinely does disrupt the nervous system, and your nervous system genuinely does need support to navigate it.

The good news is that the nervous system is extraordinarily adaptable. With the right support, it can find its footing again, even in the midst of hormonal change.