Sensory Processing Disorder (SPD) and Autism Spectrum Disorder (ASD) are two neurodevelopmental conditions that frequently appear together, leading to common confusion about their distinct natures. Both conditions involve unusual reactions to sensory input, such as sounds, textures, or lights, making their outward presentation seem similar. However, they represent separate conditions with fundamentally different core diagnostic requirements. The primary distinction lies in the central focus of each disorder: SPD is an issue of sensory information processing, while ASD is a broader challenge of social communication and interaction.
Understanding Sensory Processing Disorder
Sensory Processing Disorder describes a condition where the brain struggles to organize the sensory input it receives from the body and the surrounding environment. This neurological process affects how an individual detects, modulates, and interprets information from the traditional five senses, as well as internal senses like movement and body position. When the brain cannot correctly process these signals, it becomes difficult for an individual to produce appropriate motor or behavioral responses.
This difficulty in processing is generally categorized into three main patterns of dysfunction. Sensory Modulation Disorder involves problems regulating the intensity of sensory messages, resulting in being over-responsive (hypersensitive), under-responsive (hyposensitive), or having a persistent craving for intense sensory input. Sensory Discrimination Disorder relates to the challenge of discerning the specific qualities of sensory stimuli, such as distinguishing between two similar sounds or textures. The third pattern is Sensory-Based Motor Disorder, which affects the ability to use sensory information to plan and execute movements, often manifesting as issues with balance, coordination, or posture.
SPD is not currently listed as a standalone diagnosis in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Instead, it is recognized by many professionals, particularly occupational therapists, through specific diagnostic frameworks. This framework establishes SPD as a primary disorder of sensory input organization that can occur independently of other developmental conditions.
Understanding Autism Spectrum Disorder
Autism Spectrum Disorder (ASD) is defined within the DSM-5 as a neurodevelopmental condition characterized by persistent deficits in two core areas. The first core criterion involves significant challenges in social communication and social interaction across multiple settings. These challenges include difficulties with social-emotional reciprocity, such as the back-and-forth flow of conversation, and deficits in nonverbal communication behaviors, like abnormalities in eye contact and body language.
The second core criterion for an ASD diagnosis is the presence of restricted, repetitive patterns of behavior, interests, or activities (RRBs). This criterion requires the individual to exhibit at least two out of four possible types of behaviors. These behaviors can include stereotyped or repetitive motor movements, an insistence on strict routines or resistance to change, or highly restricted and fixated interests that are abnormal in their focus or intensity.
The fourth item listed under the restricted and repetitive behaviors criterion is the presence of hyper- or hypo-reactivity to sensory input or unusual interests in sensory aspects of the environment. This means that sensory sensitivities, such as an adverse response to specific sounds or an apparent indifference to pain, are recognized as a possible symptom of ASD. However, difficulties in social communication and interaction must also be present for an ASD diagnosis to be made.
The Fundamental Difference in Core Criteria
The most significant difference between the two conditions lies in the primary nature, or locus, of the disorder. SPD is a condition where the central nervous system struggles specifically with receiving, organizing, and responding to sensory information. The primary issue is a “traffic jam” in the brain’s sensory processing pathways, which can lead to secondary difficulties in behavior, learning, or social situations.
In contrast, ASD is a disorder focused on persistent deficits in social communication and interaction. While sensory symptoms are a recognized component of the ASD criteria, they are considered a feature of the restricted and repetitive behaviors category. Sensory sensitivities alone, regardless of severity, are not sufficient to meet the diagnostic requirements for Autism Spectrum Disorder.
A child with pure SPD may avoid wearing certain clothing due to tactile defensiveness, resulting from the brain misinterpreting the sensation of the fabric. This child might otherwise have typical language skills and a strong desire for social connection. Conversely, a child with ASD might avoid eye contact, not due to overwhelming visual input, but because of a fundamental challenge in understanding the social meaning and use of eye contact. The social and communication deficits are the defining features of ASD.
When Both Conditions Co-Occur
Despite their distinct definitions, Sensory Processing Disorder and Autism Spectrum Disorder frequently exist together in the same individual. Research suggests that a high percentage of individuals diagnosed with ASD also meet the criteria for SPD, with estimates often ranging near 90%. The overlap in symptoms, particularly the presence of sensory challenges, is the reason the two conditions are often confused.
The existence of this high co-occurrence rate highlights the need for comprehensive assessment when sensory issues are observed. A diagnosis of SPD is often given when an individual presents with significant sensory processing challenges that interfere with daily life, but lacks the persistent social communication deficits required for an ASD diagnosis. The reverse is also true; a person may have ASD and experience sensory challenges severe enough to warrant a secondary SPD diagnosis.
Comprehensive evaluations by a multidisciplinary team are necessary to accurately determine if a child’s sensory-related behaviors stem from a primary sensory processing issue, or if they are part of the broader diagnostic picture of Autism Spectrum Disorder. Understanding which disorder is present, or if both are, is necessary for developing the most appropriate and targeted support plan.