Sensory Processing Disorder (SPD) is a neurological condition where the brain struggles to receive, organize, and interpret sensory information. This difficulty stems from a breakdown in the central nervous system’s ability to make sense of the constant stream of input from the body and the outside world, rather than problems with the sensory organs themselves. This challenge affects an individual’s capacity to respond to environmental demands efficiently and appropriately.
The Core Disability: Sensory Processing Disorder
This challenge is formally known as Sensory Processing Disorder (SPD). SPD involves the brain struggling to process sensory input, making it difficult to produce an appropriate motor or behavioral response to stimuli. The senses involved extend beyond the traditional five, including the vestibular system (movement and balance), the proprioceptive system (body awareness), and interoception (internal body sensations like hunger or pain).
Sensory integration is the neurological function of processing and organizing sensation, as defined by occupational therapist Anna Jean Ayres. When this process is disrupted, it causes significant difficulties in daily life activities, affecting productivity, leisure, and self-care. While SPD can occur as a stand-alone diagnosis, it frequently coexists with other neurodevelopmental conditions, such as Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD).
Three Patterns of Sensory Processing Challenges
SPD difficulties are categorized into three primary patterns, each describing a different mechanism of processing failure. One common pattern is Sensory Modulation Disorder (SMD), which involves difficulty regulating the intensity and nature of a response to sensory input. This manifests as either sensory over-responsivity (a heightened, exaggerated reaction) or sensory under-responsivity (a diminished or delayed reaction).
A second pattern is Sensory Discrimination Disorder (SDD), characterized by the inability to interpret the specific qualities of a sensation. For instance, auditory discrimination difficulties might cause a person to struggle to distinguish between similar sounds, making it hard to follow verbal instructions. This difficulty affects any of the eight sensory systems, leading to challenges like poor spatial awareness or trouble distinguishing textures by touch.
The third pattern is Sensory-Based Motor Disorder (SBMD), where the problem lies in using sensory information to produce an appropriate motor response, affecting movement and stability. SBMD includes dyspraxia, which involves challenges with motor planning and execution, often resulting in clumsiness or difficulty learning new movements. It also includes postural disorder, which affects the ability to maintain balance and control body position during static and dynamic activities.
Manifestation in Daily Life
The internal processing challenges of SPD translate into observable behaviors that severely impact a person’s participation in everyday activities. Individuals with sensory over-responsivity often experience common stimuli as overwhelming, which can trigger a “fight, flight, or freeze” response. For example, a child might have an extreme reaction to a scratchy clothing tag, refuse to eat foods with certain textures, or cover their ears in response to a sudden, loud noise.
Conversely, those with sensory under-responsivity may appear withdrawn, lethargic, or indifferent because their nervous system requires stronger input to register a sensation. They might fail to notice a cut or bruise, or not recognize when they are hungry or need to use the bathroom. They may also constantly bump into objects without realizing it.
A third presentation is sensory-seeking behavior, where individuals constantly crave intense sensory input. This is often seen in children who cannot sit still and seek out activities like spinning, jumping, or climbing.
The motor component of SPD makes tasks requiring coordination and planning difficult to execute. A child may struggle with fine motor skills, such as holding a pencil or using scissors, or with gross motor skills like riding a bicycle or catching a ball. These difficulties can affect self-confidence and may contribute to social isolation when the individual struggles to keep up with peers in play or school activities.
Underlying Causes and Risk Factors
The precise cause of Sensory Processing Disorder is not yet fully understood, but current research indicates it is primarily a neurological condition resulting from a combination of factors. There is substantial evidence pointing to a strong genetic component, suggesting the condition can be inherited, even though specific genetic markers have not yet been identified. Researchers have also observed differences in the brain activity and connectivity of individuals with SPD when they are exposed to various stimuli.
In addition to genetic predisposition, several environmental and developmental factors are considered potential risk factors. Complications during birth, such as low birth weight or oxygen deprivation, have been associated with a higher likelihood of sensory processing difficulties. Environmental factors like prenatal exposure to toxins or a lack of appropriate sensory stimulation during early development may also play a role in the onset of SPD.
Assessment and Therapeutic Interventions
Diagnosis of Sensory Processing Disorder is typically conducted by an Occupational Therapist (OT) who specializes in sensory integration. The assessment process involves observing the individual’s reactions to various sensory experiences and gathering detailed information about their symptoms, behavior, and medical history. This comprehensive evaluation helps determine the specific patterns of processing difficulties the person is experiencing.
The most common and effective intervention is Sensory Integration Therapy (SIT), an approach led by a trained occupational therapist. This therapy is often play-based and takes place in a specialized sensory-rich environment, such as a sensory gym. The goal is to provide controlled sensory experiences that help the nervous system organize input more effectively, encouraging the individual to develop adaptive responses.
Therapists often recommend a “sensory diet,” a personalized schedule of sensory activities and environmental modifications integrated into the person’s daily routine. This tailored plan might include fidget toys, weighted blankets, or noise-canceling headphones to help manage sensory input and support self-regulation outside of the therapy setting. The intervention aims to improve daily life skills, coordination, and emotional regulation by gradually retraining the brain’s response to sensation.