Understanding Sensory Processing Disorder, RAS, and ARFID | Brain-Body Connection in Adults & Children

How Sensory Processing & the Reticular Activating System (RAS) Shape Behaviour and Regulation

For many families navigating neurodivergence — whether that’s ADHD, autism, or related developmental differences — certain challenges like sensory sensitivities, selective eating (ARFID) can feel confusing and overwhelming.

Yet, beneath those daily struggles lies a powerful network connecting the brain and body. The Craniosacral system - our sensory processing system which includes the reticular activating system (RAS) - work together to help us interpret, react, and feel safe in the world around us.

This blog explores that connection — helping parents, caregivers, and professionals understand the “why” behind behaviours and what can be done to support regulation and safety for both children and adults.

What You’ll Learn About SPD, RAS, and ARFID:

• Understanding Sensory Processing Disorder signs in children and adults

• How the Reticular Activating System (RAS) impacts attention, arousal, and sensory regulation

• What parents need to know about Avoidant/Restrictive Food Intake Disorder (ARFID)

• Practical strategies for supporting sensory processing in adults and children

Scroll down if you prefer to explore with me on YouTube!

Sensory Processing Disorder Signs: Recognizing the Hidden Struggles

Sensory Processing Disorder (SPD) happens when the brain struggles to organize and respond to sensory messages from the environment. This can involve any of our senses — touch, sound, taste, smell, movement, or internal body awareness.

While SPD is often discussed in children, sensory processing disorder in adults is common too. Adults may avoid certain textures, find noises overwhelming, or feel drained after being in sensory-rich environments.

Common Sensory Processing Disorder Signs Include:

• Strong reactions to textures, sounds, lights, or smells

• Difficulty calming down after sensory overload

• Craving movement or deep pressure (jumping, spinning, hugs)

• Emotional outbursts or shutdowns triggered by sensory overwhelm

• Avoidance of grooming activities like brushing teeth or wearing certain fabrics

When we start seeing these as nervous system responses, not behavior problems, we open the door to compassion — and to strategies that actually help.

The Reticular Activating System (RAS): The Brain’s Arousal Gatekeeper

The Reticular Activating System (RAS), which develops in utero, is a small but mighty part of the brainstem that controls alertness and attention. It acts as a “gatekeeper,” deciding what sensory information reaches conscious awareness.

For children with Sensory Processing Differences (not disorder), Autism, PDA or ADHD, the RAS might be overactive (leading to hyperarousal and sensitivity) or underactive (causing fatigue or low motivation).

How the RAS Shapes Behaviour and Focus:

• Regulates arousal and attention levels

• Filters sensory input to prevent overload

• Influences emotional regulation and self-control

• Connects with the autonomic nervous system, which controls fight, flight, or calm responses

When the RAS isn’t filtering effectively, daily life can feel like being “on” all the time — or disconnected and foggy. Gentle sensory activities, predictable routines, and body-based regulation tools can help restore balance and focus.

Avoidant/Restrictive Food Intake Disorder (ARFID): When Sensory Meets Feeding

Many families describe mealtimes as their toughest moments. What looks like “picky eating” may actually be Avoidant/Restrictive Food Intake Disorder (ARFID) — a complex feeding challenge often linked to sensory processing differences.

Children or adults with ARFID might refuse foods due to smell, color, texture, or even the sound they make when chewed. It’s not about control or stubbornness — it’s about sensory safety.

ARFID and Sensory Processing Disorder Food Connection:

• Texture sensitivity: Slimy or mushy foods may trigger discomfort.

• Smell or sound triggers: Strong odors or certain chewing sounds can cause distress.

• Color or appearance: Some people only eat certain “safe-looking” foods.

• Interoception challenges: Difficulty sensing hunger or fullness.

As The Therapeutic Edge notes, ARFID overlaps frequently with SPD, anxiety, and autism — showing that eating challenges are often rooted in the body’s protective sensory responses, not defiance.

Creating safety and trust around food — instead of pressure — allows for gradual desensitization and positive sensory experiences.

Sensory Processing Disorder and Food: The Brain-Body Relationship

The relationship between Sensory Processing Disorder and food extends beyond preference — it’s a full-body experience.

Oral, motor, and gut sensations are all linked back to our nervous system, both experiencing and sending messages out to our body. Some children struggle with processing, while others are hyper-sensitive. Some may have great dexterity and motor control, while others struggle.

Here Are Some Gentle Ways to Support Healthy Eating Habits:

• Keep mealtimes predictable and calm

• Try new foods together, without any pressure

• Respect sensory limits while gently expanding exposure

• Collaborate with skilled professionals, like occupational therapists or feeding specialists

The goal isn’t perfect eating — it’s helping the child (or adult) feel safe in their body again... and if we force the issue (even when it's out of worry), our children feel it but the body just sees it as lack of safety, furthering the issue.

Hypotonia: The Physical Layer of Sensory Regulation

Low muscle tone (hypotonia) can make sensory and feeding challenges even harder. These physical factors influence posture, coordination, and how sensory signals travel through the body.

Children with hypotonia might tire quickly during meals, struggle to sit upright, or find fine motor tasks exhausting. When the body is working overtime to stay stable, there’s less capacity left for focus, learning, or emotional control.

Gentle physical support — such as core-strengthening activities, occupational therapy, or craniosacral work — can create a stronger foundation for sensory integration and self-regulation.

Sensory Processing Disorder in Adults: Lifelong Awareness and Healing

Many adults realize they struggle with sensory processing only after seeing it in their children. They may remember struggling with clothing tags, bright lights, or noisy environments but never had words for it.

Recognizing sensory processing disorder in adults is empowering — it validates lived experiences and provides practical ways to care for one’s nervous system.

Self-Support Strategies for Adults:

• Identify triggers and plan sensory breaks

• Use calming input (weighted blankets, music, or mindful movement)

• Create sensory-friendly spaces at home or work

• Seek coaching or therapy that respects sensory needs

This awareness isn’t about labeling — it’s about self-understanding and giving the body what it needs to thrive.

Supporting the Whole Nervous System

Sensory processing, the Reticular Activating System, ARFID, and other sensitivities are deeply connected — and together, they shape how we experience and respond to the world.

When we understand these systems, we stop trying to “fix” behaviour and instead focus on supporting our children through compassion, sensory-informed strategies, and body-based care. We can help our children find their unique rhythm from a space of safety and connection.

Because when the nervous system feels safe — growth, learning, and joy naturally follow.

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If you have any questions, please feel free to reach out!

🌺 Katie

Please note that this information is intended for educational purposes only and should not be considered medical advice. Always consult with a healthcare professional for personalised guidance.