What Causes Sensory Processing Disorder (SPD)?

If you’ve ever wondered why everyday things — like bright lights, background noise, or even the tag in your shirt — feel unbearable when others barely notice them, you’re not alone. For many, the answer lies in something called Sensory Processing Disorder (SPD).

SPD is a condition where the brain struggles to organize and respond to sensory information. To put it simply: the messages coming in from your senses (touch, sound, movement, or even internal body signals) don’t get processed in the same way they do for most people. The result? Ordinary sensations can feel overwhelming, irritating, or even painful.

But what actually causes SPD? While researchers don’t have every answer yet, the science we do have points to some important factors. Let’s break them down.

1. Brain Wiring Differences

Research shows that people with SPD have differences in how their brains are wired. One study found that boys with SPD had lower white matter connectivity in the parietal region of the brain. Think of white matter like the brain’s “highway system,” connecting different regions so messages can travel back and forth.

If those highways aren’t working well, sensory signals can get delayed or scrambled. That’s why someone with SPD might react strongly (or not at all) to sensory input. Studies also show measurable differences in things like sweat response (skin conductance) and brain wave patterns, confirming that their nervous systems react differently to the world around them.

2. Genetics

There’s strong evidence that sensory differences run in families. If a parent or sibling experiences sensory challenges, it’s more likely that others in the family will too. Researchers are still looking into the specific genes involved, but heredity clearly plays a role.

3. Prenatal and Birth Factors

Certain experiences before, during, or shortly after birth can raise the likelihood of SPD, such as:

Low birth weight (under 2.2 kg / 5 lbs)
Premature birth (before 32–36 weeks) — one study found that 46% of babies born before 32 weeks later showed signs of SPD
Maternal stress, illness, or substance exposure during pregnancy
Traumatic or emergency births and surgeries

These experiences can impact early brain development and the nervous system’s ability to process the world smoothly.

4. Environmental Influences

Early life environments also matter. Both too much sensory input (like constant noise or overstimulation) and too little (like not enough varied experiences) during critical stages of development can shape how the brain learns to respond to the world. Exposure to toxins or pollution may also play a role.

SPD and Co-Existing Conditions

SPD rarely appears in isolation. It often shows up alongside other diagnoses:

Autism Spectrum Disorder (ASD): Research suggests that 77–95% of autistic adults experience sensory challenges. In fact, sensory differences are now part of the official autism diagnosis in the DSM-5.
ADHD: Many with ADHD also experience unusual sensory reactions. A 2017 review even suggested that sensory differences may be a core feature of adult ADHD, not just a side effect.
Mental health conditions: People with SPD frequently report anxiety, depression, OCD, PTSD, and more. Sensory overwhelm can fuel anxiety — and anxiety, in turn, can make sensory sensitivity worse, creating a feedback loop. Elevated cortisol levels (a stress hormone) have even been found in highly sensitive individuals.
Other neurodevelopmental conditions: Such as learning disabilities or developmental coordination disorder.

The Recognition Challenge

Even with growing research, SPD is not officially listed as a standalone diagnosis in manuals like the DSM-5 or ICD-11. Instead, it’s often described as a feature of other conditions. This can make getting formal recognition or support harder — but it doesn’t make your experience any less real or valid.

Putting It All Together

So, what causes SPD? The best answer is that it’s a combination of factors: genetics, brain wiring, prenatal and birth experiences, and environmental influences. And while it often co-occurs with other conditions like autism, ADHD, or anxiety, SPD itself is a very real way of experiencing the world.

What matters most isn’t just pinpointing the cause — it’s understanding your sensory needs and building strategies that support you in daily life.

Next Steps

If this resonates with you, you’re not “too sensitive.” You’re navigating a brain and body that process sensory input differently. That deserves recognition, compassion, and practical support.

Would you like a FREE Sensory Overload Checklist — a simple, practical tool to help you recognise the signs and patterns that show you’re nearing your sensory limit? Click the link below:

Free Sensory Overload Checklist