Sensory Processing Disorder (SPD) is a neurological condition that affects how the brain receives, organizes, and responds to sensory information from the environment and the body. The brain struggles to integrate these signals, leading to atypical responses to ordinary stimuli such as sounds, touch, sight, or movement. This challenge impacts an individual’s ability to participate effectively in daily activities, leisure, and social interactions.
The condition involves processing input from all eight sensory systems, including the five well-known senses, vestibular (balance and movement), proprioceptive (body awareness), and interoceptive (internal body sensations like hunger or pain). SPD is diagnosed when these processing difficulties significantly interfere with functional performance across different areas of life.
The Three Categories of Sensory Processing
The clinical structure of Sensory Processing Disorder is categorized into three main patterns, which describe how the processing challenges manifest. The first pattern is Sensory Modulation Disorder (SMD), which involves difficulty regulating the intensity and nature of responses to sensory stimuli.
Sensory modulation is the central nervous system’s process of adjusting neural messages about the intensity, frequency, and duration of sensory input. SMD has three distinct subtypes: Sensory Over-Responsivity (SOR), Sensory Under-Responsivity (SUR), and Sensory Seeking (SS). Individuals with SOR have a heightened response to stimuli, while those with SUR may be unaware of stimuli or exhibit a delayed, muted response.
Sensory Discrimination Disorder (SDD) is the second pattern, characterized by the incorrect processing of sensory information and difficulty distinguishing between similar sensations. This challenge relates to the interpretation of input, not the intensity of the response. Discrimination difficulties can affect any sensory system, such as struggling to tell the difference between similar visual shapes or identifying an object by touch alone.
For example, auditory discrimination issues can impede language processing, making it difficult to differentiate between similar-sounding words or filter out background noise. Proprioceptive discrimination challenges might cause a person to struggle with knowing how much force is needed to handle an object, leading to squeezing it too hard or too lightly.
The third category is Sensory-Based Motor Disorder (SBMD), where the difficulty lies in using sensory information to produce an appropriate, organized motor response. SBMD includes two subtypes: Postural Disorder and Dyspraxia.
Postural Disorder involves challenges with maintaining normal posture and controlling body position, affecting balance and stability during movement. Dyspraxia, also referred to as developmental coordination disorder, is characterized by difficulties with motor planning and execution. This affects the ability to conceive, plan, and perform skilled movements, often resulting in apparent clumsiness.
Common Signs and Behaviors
The challenges inherent in SPD manifest as a wide range of observable behaviors that impact daily life and social functioning. For those experiencing Sensory Over-Responsivity (SOR), everyday environments can feel overwhelmingly intense, leading to sensory avoidance behaviors. This hypersensitivity appears as extreme distress in response to specific textures, such as an aversion to clothing tags or a refusal to wear certain fabrics.
Auditory hypersensitivity often results in a fearful response to sudden, loud, or high-pitched noises, causing the individual to cover their ears or become distracted by background sounds. Tactile defensiveness may cause a person to withdraw from light touch or avoid messy play. Taste and smell sensitivities can lead to highly restricted eating habits, where food is rejected based on texture, temperature, or odor.
Individuals with Sensory Under-Responsivity (SUR) or Sensory Seeking (SS) behaviors often exhibit a need for intense sensory input to register a sensation. This hyposensitivity can result in a high pain tolerance or an unawareness of temperature extremes. They might also struggle to recognize internal body cues, such as hunger or a full bladder. Sensory seeking manifests as a constant need for movement, often involving spinning, rocking, or crashing into objects and people. These individuals may frequently touch objects or enjoy excessively loud music or bright environments.
Difficulties in motor planning and coordination are also common. Individuals may appear clumsy, struggle with simple tasks like buttoning a shirt or tying shoelaces, or have poor balance. This is due to the brain’s difficulty translating sensory information about body position into efficient, planned movement, not muscle weakness.
Diagnosis and Therapeutic Approaches
The diagnosis of Sensory Processing Disorder is a multi-step process conducted by a trained Occupational Therapist (OT) specializing in Sensory Integration. Since there is no single medical test, the diagnosis relies on a comprehensive evaluation of the individual’s sensory processing patterns. This evaluation begins with detailed parent or caregiver questionnaires, such as the Sensory Profile, to provide context about the person’s behavior in daily settings.
The OT also performs structured clinical observations, engaging the individual in play-based activities designed to elicit sensory responses and assess real-life movements. Standardized assessment tools may be used to evaluate specific aspects of motor planning, balance, and the integration of tactile, vestibular, and proprioceptive sensations. The combination of testing, observation, and parent reports allows the therapist to determine the functional impact of sensory challenges.
Once a diagnosis is established, the primary intervention is Occupational Therapy utilizing a Sensory Integration (OT-SI) approach. This therapy is conducted in a specialized sensory-rich environment, often featuring suspended equipment like swings and crash mats. The goal is to help the nervous system organize sensory input more effectively by providing controlled sensory experiences.
Therapy sessions are play-based and tailored to the individual’s specific sensory needs, encouraging active engagement in sensory-motor tasks. This structured engagement aims to improve the brain’s ability to process and respond to sensations, leading to more adaptive behavioral outcomes. Supporting strategies include the development of a “Sensory Diet,” a personalized schedule of sensory activities and environmental modifications designed to regulate the nervous system throughout the day.