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Sensory Processing Disorder vs. Autism: Understanding the Differences

April 13, 2021


Sensory processing disorder (SPD) is often confused with autism spectrum disorder (ASD) due to the similarities and connections that exist. While the two have many similarities, SPD is often a comorbid symptom of ASD, but not all children with sensory processing disorder have autism.

Sensory Processing Disorder vs. Autism: Understanding the Differences

What is autism?

Autism is a developmental disorder which, according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), has certain criteria for the diagnosis. Human development occurs in stages with milestones that are met or exceeded over time. During the early stages of a child’s development, children begin to communicate and socialize, beginning with their parents, while reacting to and showing emotions. Deficiencies that persist in these areas could be a problem. A child may repeat certain behaviors or have restrictive mannerisms or interests. Some children may show stimming behavior, such as hand flapping and repetitive noises, while others may need a toy to be placed in exactly the same spot each time, with a dislike for any disruption or change.

Autism can cause a child to learn, react, and attend to details differently. If an intellectual disability or an intellectual developmental disorder is not the sole cause of these deficiencies, with a child’s socialization and communication being below what is typical for their level of development, this could be a sign of autism. Because there is no medical test to diagnose, a doctor would need to look at the developmental milestones and the child’s behavior, while taking into account any parental input about the child. 

Autism spectrum disorder (ASD) is named due to the spectrum of disorders within the category. These would include autistic disorder, asperger’s syndrome, and pervasive developmental disorder not otherwise specified (PDD-NOS).

The causes for autism are not known, however some factors may be biological (possibly related to having older parents) or genetic (in which chromosomal conditions create a greater chance of having ASD, and having a sibling with the condition leading to a higher risk.) Environmental factors have also been considered, and the prescription drugs, valproic acid or thalidomide, while used in pregnancy, have been associated with a higher risk.

While there is no cure for autism, early treatment is better for development, with therapy aiding in speech delays, walking, and social interaction. The Individuals with Disabilities Education Act (IDEA) states that a child under the age of 36 months who may have a developmental delay could possibly qualify for services within their local district.

What is sensory processing disorder?

Sensory processing is the way a person’s brain perceives sensory information and how that person responds to that information. A person with sensory processing disorder (SPD) has an impairment in the way their brain processes the sensory information that is used to regulate behavior and motor function/performance such as balance, walking, and coordination. They may react to sensory stimuli in a socially or emotionally negative way, and this could affect their behavior or the way other people respond to them.

Originally called “sensory integration dysfunction,” it is said to affect approximately 5-16% of school-aged children in general. Many children with SPD may be extremely sensitive to the way certain things feel, look, or sound; they may be distracted more easily; and their fine motor skills may be lacking.

Sensory processing involves eight components: the five senses – taste, smell, hearing, seeing and touch; as well as three other components. Vestibular function and proprioception are sometimes referred to as the “sixth and seventh sense.” 

Proprioception is a sense of one’s own body movement or position, so that if a child lifts their hand, they are aware that they are doing that action. Vestibular function is the inner ear and brain working together to help control movement of the eyes, body balance, and one’s awareness of their own body in relation to other objects around them. 

The final component, interoception, is the awareness of what is happening within one’s own body. For example, a person can feel how hot or cold an object is through their skin or know when they are thirsty or hungry. Being aware of one’s own heart rate is another example, as well as the link between emotions and the body’s reaction to those feelings.

In regard to sensory issues, most information refers to two types:

1. Hyper sensitivity 

Hyper sensitivity is when a child is easily stimulated by sensory stimuli. The child may have a low tolerance for pain, some coordination issues, and/or they could be sensitive to certain sights or sounds such as bright lights or noisy appliances. A child with this may also be a finicky eater.

2. Hypo sensitivity

Hypo sensitivity is when a child does not have enough sensory stimulation. The child may have a high pain tolerance, may bump into surrounding walls or objects, and may have a need to touch or mouth items.

One study showed that children who were more fearful or had anxiety, as well as premature babies or those with birth complications, might present with more sensory issues.

Some diagnostic classification guides include sensory processing disorder, however, it is not listed as an “official” disorder in the Diagnostic and Statistical Manual of Mental Disorders – Fifth Edition (DSM-5).


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Connections between sensory processing disorder and autism spectrum disorder

Some experts have found that over 80% of children with autism also have sensory processing disorder, and the DSM-5 includes “hyper or hypo reactivity to sensory input,” listing this as one of the behaviors associated with ASD.

The STAR Institute for Sensory Processing in Colorado has conducted studies finding that “at least three quarters of children with autistic spectrum disorders have significant symptoms of sensory processing disorder, and probably more depending on how significant symptoms are defined.” Yet, many studies show that the reciprocal of this discovery is not a fact. Most children who have SPD do not have ASD.

Roya Ostovar, PhD, is the Director of McLean Hospital’s Pathways Academy in Belmont, Massachusetts and an Assistant Professor of Psychology, Department of Psychiatry at Harvard Medical School. Dr. Ostovar noted that people with SPD don’t show the traits of someone with autism, such as difficulties with social and communication skills or stimming behaviors such as repetitive sounds or movement.

Differences between autism and sensory processing disorder

Studies have been conducted to show the differences between children with autism spectrum disorder and sensory processing disorder. In one study, 210 participants were included with 68 having autism spectrum disorder, 79 having sensory processing disorder, and 63 with typical development (TD). Any child who had ASD with SPD was not included in the study. 

Children were scored for Sensory Over-Reactivity (SOR), where sensory items bother a child; Sensory Under-Reactivity (SUR), where sensory items were not noticed by the child; and Sensory Craving (SC), where the child needed certain sensory stimulation. They were also scored for their Empathy Quotient (EQ), or how easily or strongly they reacted to or were able to gauge another person’s feelings. Finally, the children were scored for their Systemizing Quotient (SQ), or how interested the child was in understanding how the internal components of a machine worked.

They found that for Sensory Under-Reactivity, the ASD group scored higher than the SPD group, which scored higher than the TD group. For Sensory Over- Reactivity, the ASD and SPD groups were relatively the same, but much higher than the TD group. For Sensory Craving, the ASD and SPD groups were about the same as each other, but with higher scores than the TD group. In the category of Systemizing Quotient, children with ASD scored higher than both the SPD and TD groups. 

Finally, in regard to Empathy Quotient, ASD children scored lower than SPD and TD, although children with SPD scored lower than TD children in this area. The Empathy Quotient scores were also affected by gender, with girls scoring higher than boys. The ASD group showed difficulties in empathy, with higher scores in systemizing as compared to both of these areas in the SPD and TD groups, both of whom scored in the average range. Using empathy and systemizing as a factor to help differentiate between autism spectrum disorder and sensory processing disorder will help to improve the diagnostic criteria being used.

At the University of California – San Francisco (UCSF) Benioff Children’s Hospital, a study looking at the structural connections of the sensory area of the brain were conducted on children with ASD, SPD, and typically developing boys. With an advanced type of Magnetic Resonance Imaging (MRI) called Diffusion Tensor Imaging (DTI), a measurement was taken to gather information about the white matter tracts of the three groups’ brains. The white matter contains the connections that link together different areas of the brain that help a person with cognition, perception and movement so that they can see something, contemplate it, and act upon it. Through the imaging, researchers were able to see the course of the white matter “wires” as well as the cohesion.

The study was conducted on males in the age range of 8 to 12, 16 of whom had Sensory Processing Disorder, 15 with autism, and 23 who were typically developing. Elysa Marco, MD, a cognitive and behavioral pediatric neurologist specializing in children with sensory processing disorder, autism and other neurodevelopmental conditions led the study which revealed that only the ASD group had impairments in the part of the brain which helps with recognizing facial emotion, memory, and social processing. Children with SPD showed more brain disconnection in some of the tracts dealing with sensory issues than the subjects with autism. These abnormal white matter tracts at the back of the brain are where the systems for sensory processing are located.

Senior author of the study and Professor of Radiology and Biomedical Imaging and Bioengineering at UCSF, Pratik Mukherjee, MD, PhD determined that because of the location of the abnormalities, this could indicate SPD as being distinguishable from other neurodevelopmental disorders. He believes that it is important to find the neurological reasons behind ASD and SPD and pinpoint areas of overlap and distinction. He also feels that findings from their research could provide a biological root for SPD which could then be measured and used for future diagnoses.

A previous study done in 2006 with twins showed that if one child was hypersensitive to light or sound, the other would also have that sensitivity, revealing the possible genetic element.

SPD or ASD: finding the right diagnosis

It is important for parents to find a professional who can provide the correct diagnosis, as early as possible, so children can receive the appropriate treatment. Many doctors will try to help alleviate the sensory issues while treating the autism spectrum disorder, if that diagnosis applies.

Various skills that a child learns to do at different age levels is called a developmental milestone, and according to the Centers for Disease Control and Prevention (CDC), “

The American Academy of Pediatrics recommends that children be screened for general development using standardized, validated tools at 9, 18, and 30 months and for autism at 18 and 24 months or whenever a parent or provider has a concern.” The CDC website has a list of the milestones by months and years, which parents can check to compare their child’s progress and discuss with the pediatrician if there is a concern. Once it has been determined that the child is falling behind on any of the milestones, and if there is a concern of autism spectrum disorder, a recommendation should be made for the child to be examined by a specialist. This could be a developmental pediatrician, a pediatric neurologist, or possibly a child psychologist or psychiatrist.

Also, a qualified Occupational Therapist (OT) with training in the area of sensory integration can do an evaluation to determine if a child has sensory processing disorder. Since there are no formal diagnostic criteria, a child’s behavior and their interactions would be observed to see if any sensory issues were present.

Additionally, a qualified and trained therapist can perform an assessment called a Sensory Integration and Praxis Test (SIPT) or a Sensory Processing Measure (SPM). The SIPT measures sensory processing or sensory perception of children aged four years to eight years, 11 months as it relates to the developing language skills, social interactions and educational performance. The SPM measures sensory processing, planning or ideas (praxis), and social engagement in the home, school and other social realms.

Is there a treatment for sensory processing disorder?

At this time there is no treatment for SPD, but there are ways to help manage the sensory issues. A highly trained Occupational Therapist (OT) can focus on each child’s individual sensitivities, providing them with the appropriate amount of activities based on their needs. A swing can provide necessary movement for a child who needs stimulation, while the use of a soft-bristled sensory brush may be used for a child who has an aversion to touch or certain sensations against their skin. Sensory Integration therapy exposes a child to a variety of accommodations, activities, and treatments.

Because sensory processing is not listed as an actual disorder, many experts hesitate to use treatments that are not backed by a lot of research showing the effectiveness in helping to change these behaviors. The American Academy of Pediatrics warns that “parents should be informed that the amount of research regarding the effectiveness of sensory integration therapy is limited and inconclusive.”

Dr. Marco believes that measuring and observing brain connectivity will help to see which interventions are successful for the various neurodevelopmental issues. With more research, determination can be made to find out what the genetic links are for the varied sensory processing issues. They will also be able to determine what risks, if any, there may be for SPD, and whether the interventions being used at the current time are useful in the change and adaptation of the brain. Finally, researchers may be able to develop new therapies based on any up-to-date findings.

Dr. Ostovar feels that children with sensory processing disorder will not outgrow this. However, the disorder can be managed in a way that helps them adapt and still behave in a socially conventional manner.

Final thoughts on sensory processing disorder and autism 

A child with autism spectrum disorder may have sensory processing issues, however a child with sensory processing disorder does not have autism.

  • If a parent believes their child has any issues regarding a developmental delay, they should contact their pediatrician for an evaluation
  • If a child shows any signs of a low tolerance to any sensory stimuli; has an excessive need for stimulation, such as needing to mouth certain objects; or is showing any coordination issues or bumping into walls or objects, the pediatrician should be made aware
  • With regard to any child who has already been diagnosed with autism and has sensory issues or is found to have sensory processing disorder, a parent should do their research to provide the best help possible for their little one. Talk to the pediatrician and other trusted professionals for recommendations, and search the internet for websites and groups for more information and guidance

The earlier a child with autism and/or sensory processing disorder receives early intervention and help, the better.

References:

https://www.cdc.gov/ncbddd/autism/facts.html

https://www.cdc.gov/ncbddd/actearly/milestones/index.html https://doi.org/10.1016/j.dcn.2017.05.005

https://images.pearsonclinical.com/images/assets/basc- 3/basc3resources/DSM5_DiagnosticCriteria_AutismSpectrumDisorder.pdf   

https://www.mayoclinic.org/diseases-conditions/autism-spectrum-disorder/diagnosis- treatment/drc-20352934#:~:text=If%20your%20child%20shows%20any, developmental%20pediatrician%2C%20for%20an%20evaluation

http://middletown.ttl-stage.com/best-practice-sensory/wp- content/uploads/sites/3/2015/07/CASE-SMITH-2014.pdf

https://www.pearsonclinical.co.uk/AlliedHealth/PaediatricAssessments/Sensory/SPM/sensory- processing-measure.aspx

https://pediatrics.aappublications.org/content/129/6/1186 https://www.researchgate.net/publication/241697463

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