Mindly Different

What Your Nervous System Is Responding To

Sensory sensitivity is often described as a fixed trait – something you either “have” or don’t. But many people discover, sometimes unexpectedly, that their tolerance for stimulation shifts over time. Sounds that once faded into the background become intrusive. Crowded spaces start to feel heavy. Light, touch, or emotional intensity suddenly take more effort to process.

When this change happens, it can be deeply unsettling.
People often ask themselves: “What’s wrong with me? Why can’t I handle what I used to?“

From a neuroscience perspective, this kind of shift is rarely accidental. Heightened sensitivity usually reflects a nervous system that is working closer to its limits. The brain’s natural filtering systems – the mechanisms that help prioritize, soften, and recover from sensory input – are under greater strain.

This doesn’t mean the brain is breaking down. It means it has fewer reserves available to shield itself from stimulation.

Sensitivity, in this sense, is not weakness. It is a signal – an honest indicator of a nervous system that is adapting to its current biological load.

The Brain’s Sensory Filter Is Not Fixed

Under typical conditions, sensory information passes through layers of regulation before it reaches conscious awareness. Structures like the thalamus, prefrontal cortex, and inhibitory networks help decide what deserves attention and what can remain in the background.

When this filtering system is well-resourced, the brain can:

• ignore irrelevant noise
• tolerate crowded environments
• recover quickly after stimulation
• regulate emotional reactions tied to sensory input

But many conditions – neurological, hormonal, psychological, or metabolic – can temporarily or permanently weaken this filtering system.
When that happens, the world gets louder, brighter, faster, closer.

Neurological Conditions

After a concussion, stroke, or other acquired brain injury, sensory sensitivity is extremely common – even when imaging looks “normal” or the injury is labeled mild.
This happens because:

• neuronal membranes become more excitable
• inhibitory signaling (often GABA-based) is reduced
• recovery cycles after stimulation slow down
• sensory integration networks are reorganizing

A person recovering from concussion may feel irritated by normal conversation, overwhelmed by grocery stores, or exhausted by screen light. The brain is spending more energy just maintaining basic stability, leaving less capacity for sensory regulation.

Migraine offers another example. During migraine phases, the sensory cortex becomes hyper-responsive, and the thalamus – the brain’s sensory relay center – becomes less effective at gating input. Light, sound, smell, and even touch can become painful rather than neutral. Epilepsy (even between seizures) may highten sensory reactivity in some individuals due to increased cortical excitability and altered inhibitory control (GABAergic systems).

Hormonal Transitions: When Neurochemistry Shifts

Hormones play a powerful role in sensory regulation, particularly estrogen, progesterone, and cortisol.

During perimenopause and menopause, fluctuating estrogen levels affect:

• serotonin (mood and emotional stability)
• dopamine (motivation and reward)
• GABA (inhibition and calm)

As a result, many women report:

• increased irritability
• intolerance to noise or multitasking
• emotional reactivity
• feeling overstimulated by environments that once felt manageable

This is not psychological weakness. It is neurobiology.

Similarly, pregnancy and the postpartum period combine hormonal shifts with sleep deprivation, which further reduces sensory filtering and emotional resilience.

Thyroid disorders – both hyper- and hypothyroidism – can also alter neural firing rates and sensory perception, making stimulation feel intrusive or overwhelming.

Mental Health and Trauma-Related Conditions

Traumatic experiences recalibrate the nervous system toward vigilance.

In PTSD and complex trauma, the amygdala becomes more reactive, while prefrontal regulation is often reduced. The brain prioritizes threat detection over comfort. Sensory input is no longer neutral – it is scanned for danger.
This can show up as:

• sound sensitivity
• startle responses
• difficulty tolerating crowds or unpredictability
• strong reactions to tone of voice, facial expressions, or sudden movement

Chronic anxiety and burnout produce similar effects over time. Prolonged stress increases allostatic load – the cumulative wear on regulatory systems – making the brain less able to dampen sensory input. Even short-term sleep deprivation can dramatically increase sensitivity, weakening emotional regulation, sensory gating and cognitive resilience. In depression (especially with agitation or burnout), reduced cognitive energy and impaired regulation can make stimulation feel overwhelming rather than manageable.

Neurodevelopmental Differences

For people with neurodevelopmental conditions, sensory sensitivity often exists from early life. Differences in thalamocortical connectivity, sensory integration, and executive regulation mean that the brain may process input with higher precision but less filtering.

Under stress, illness, hormonal change, or fatigue, this baseline sensitivity often intensifies – not because the brain is failing, but because it is working harder with fewer resources.

Systemic and Inflammatory Conditions

Conditions like long COVID, autoimmune disorders, and chronic pain syndromes often involve:

• neuroinflammation
• autonomic nervous system dysregulation
• altered cerebral energy metabolism

These changes can sensitize neural tissue, making everyday sensory input feel exhausting or painful. In fibromyalgia, for example, central sensitization causes the nervous system to amplify signals that would otherwise be filtered out.

A Shared Mechanism Beneath Many Conditions

Across all these experiences, the pattern is remarkably consistent.
Sensory sensitivity increases when:

• excitation outweighs inhibition
• recovery cycles slow down
• cognitive and emotional regulation demand more energy
• the nervous system operates closer to its limits

Sensitivity is not a failure of tolerance.
It is a signal of load.

Listening Instead of Fighting

When sensory sensitivity increases, the instinct is often to push through, adapt harder, or blame oneself. But from a biological perspective, the nervous system is asking for:

• reduced input
• more predictable environments
• longer recovery windows
• gentler pacing

Sensitivity is not an enemy to overcome.
It is information – precise, embodied, and meaningful.

Understanding when and why it increases allows us to respond with care instead of force, and with respect instead of shame.

Your nervous system is not broken. It is communicating.
And learning to listen is one of the most powerful forms of brain health there is.

By Nataliya Popova
Mindly Different – Coaching for the beautifully different mind