The human brain constantly receives and organizes information from the environment through various sensory channels. This process, known as sensory processing, involves not just the familiar five senses, but also internal systems that monitor balance, body position, and internal states. When this neurological organization is challenged, the result is a difference in how a person perceives and responds to the world. While these sensory differences are commonly associated with broader neurodevelopmental conditions, they can and often do occur independently, impacting daily function for many individuals.
Defining Sensory Processing Differences
Sensory processing differences reflect a challenge in the brain’s ability to efficiently handle incoming sensory information. This manifests in three primary patterns describing how the nervous system responds to input.
A common pattern is sensory over-responsivity, or hypersensitivity, where a person is quickly overwhelmed by stimuli others find tolerable. For example, the sound of a rustling leaf or the feeling of a clothing tag might trigger a strong, negative emotional or behavioral reaction.
Conversely, sensory under-responsivity, or hyposensitivity, involves a diminished or delayed reaction to sensory input. These individuals may appear unaware of stimuli, such as failing to notice pain or extreme cold, requiring more intense stimulation to register the input.
This often leads to a third pattern: sensory seeking or craving. Sensory seeking involves an active pursuit of intense sensory experiences to achieve a “just-right” level of arousal. This may look like constant movement, such as spinning or jumping, or an excessive need to touch every object encountered. An individual may experience a combination of these patterns across different sensory systems.
Sensory Processing Disorder as a Standalone Diagnosis
Sensory issues can be the primary challenge for an individual, recognized clinically as Sensory Processing Disorder (SPD). This condition describes a neurological difficulty in detecting, modulating, or interpreting sensory stimuli that causes impairment in daily functioning. For a diagnosis of SPD, these difficulties must be chronic, pervasive, and significantly interfere with life activities, learning, or social participation.
It is important to note that this diagnosis is not currently included in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). However, the concept is widely used by occupational therapists specializing in sensory integration and is supported by neurological research. Studies have shown measurable differences in the brains of children with SPD compared to those who are neurotypical, specifically involving white matter tracts related to sensory processing.
For SPD to be considered a standalone condition, the sensory challenges must not be better explained by meeting the diagnostic criteria for other neurodevelopmental conditions. When sensory issues are the main source of distress and dysfunction, and the individual does not have the broader developmental profile of another condition, SPD provides a framework for targeted support focused on sensory integration techniques.
Sensory Sensitivity as a Core Feature of Autism
The connection between sensory differences and neurodevelopmental conditions is strongest in the context of Autism Spectrum Disorder (ASD). In the DSM-5, sensory hyper- or hyporeactivity, or unusual interests in sensory aspects of the environment, were formally integrated into the diagnostic criteria for ASD. This inclusion acknowledges that atypical sensory processing is a core component of the autistic experience.
These sensory manifestations are classified as one of the four types of restricted, repetitive behaviors required for an ASD diagnosis. For instance, a person with ASD may exhibit a strong adverse response to specific textures or sounds (hyper-reactivity). Alternatively, they might show indifference to pain or temperature (hypo-reactivity) or engage in visual fascination with spinning objects or lights (unusual sensory interest).
In ASD, the sensory profile is part of a complex neurodevelopmental foundation that impacts nearly every aspect of life, alongside persistent challenges in social communication and social interaction. This differs from SPD, where the sensory difficulties are the primary diagnostic concern.
Other Conditions That Include Sensory Challenges
Sensory processing challenges are not exclusive to either standalone SPD or ASD; they are highly common in a range of other mental health and neurodevelopmental conditions.
Attention Deficit Hyperactivity Disorder (ADHD)
ADHD frequently co-occurs with sensory differences, with studies estimating that a significant percentage of children with ADHD show symptoms of sensory over-responsivity. For these individuals, difficulty filtering stimuli can look like inattention or hyperactivity, as their nervous system struggles to manage a bombardment of sensory input.
Anxiety and Trauma
Anxiety disorders also have a strong link, as heightened sensory input can trigger or worsen anxious responses and lead to avoidance behaviors. The brain’s threat detection system may be overly sensitive, interpreting normal sensory events as dangerous. Similarly, individuals who have experienced Complex Trauma or Post-Traumatic Stress Disorder (PTSD) often develop hypersensitivity to certain environmental cues, constantly scanning the environment for perceived threats.