The exact cause of Sensory Processing Disorder–like the causes of ADHD and so many other neurodevelopmental disorders–has not yet been identified. However, preliminary studies and research suggest some leading contenders.
- from Sensational Kids: Hope and Help for Children With Sensory Processing Disorder (2014) by Lucy Jane Miller, PhD, OTR
Sensory processing (originally called "sensory integration dysfunction" or SID) refers to the way the nervous system receives messages from the senses and turns them into appropriate motor and behavioral responses. Whether you are biting into a sandwich, riding a bicycle, or reading a book, your successful completion of the activity requires accurate processing of sensation.
Sensory Processing Disorder (SPD), exists when sensory signals are either not detected or don't get organized into appropriate responses. Pioneering occupational therapist, educational psychologist, and neuroscientist A. Jean Ayres, PhD, likened SPD to a neurological "traffic jam" that prevents certain parts of the brain from receiving the information needed to interpret sensory information correctly. A person with SPD finds it difficult to process and act upon information received through the senses, which creates challenges in performing countless everyday tasks. Motor clumsiness, behavioral problems, anxiety, depression, school failure, and many other problems may impact those who do not have effective treatment.
One study (Ahn, Miller, Milberger, McIntosh, 2004) shows that at least 1 in 20 children’s daily life is affected by SPD. Another research study by Alice Carter and colleagues who are members of the Sensory Processing Disorder Scientific Work Group (Ben-Sasson, Carter, Briggs-Gowen, 2009) suggests that 1 in every 6 children experiences sensory symptoms that may be significant enough to affect aspects of everyday life functions.
Symptoms of Sensory Processing Disorder, like those of most disorders, occur within a broad spectrum of severity. While most of us have occasional difficulties processing sensory information, for children, adolescents, and adults with SPD, these difficulties are chronic, and they can significantly disrupt everyday life.
What Sensory Processing Disorder Looks Like
Sensory Processing Disorder can affect people in only one sense–for example, just touch or just sight or just movement–or in multiple senses. One person with SPD may over-respond to touch sensation and find clothing, physical contact, other tactile sensory input to be unbearable and/or they may respond to visual or auditory or another sensory input. Another person might under-respond and show little or no reaction to stimulation, even pain or extreme hot and cold or just may be slow to respond to sensation. In children whose sensory processing of messages from the muscles and joints is impaired, posture and motor skills can be affected. These children have postural disorder and are the "floppy” children who prop themselves up on walls when standing, lean over on their hand when writing and love to hang out, but not to move. The old fashioned “couch potato” now turned “mouse potato” as society becomes 2-dimensional (auditory and visual) with I-Pads, I-watches and I-everything! In yet another subtype (dyspraxia) children are awkward and clumsy and get called "klutz" and "spaz" on the playground, always the last to be picked for a team in PE. Still other children exhibit an appetite for sensation that is in perpetual overdrive, we call these children sensory cravers. They seem almost addicted to intense stimulation but when they get they become dysregulated. These kids often are misdiagnosed - and inappropriately medicated - for ADHD.
Sensory Processing Disorder is most commonly diagnosed in children, but people who reach adulthood without treatment also may experience significant symptoms and continue to be affected by their inability to accurately and appropriately interpret sensory messages.
These "sensational adults" may have difficulty performing routines and activities involved in work, close relationships, and recreation. Because adults with SPD have struggled for most of their lives, they may also experience depression, underachievement, social isolation, and/or other secondary effects.
Sadly, misdiagnosis is the rule rather than the exception because many health care professionals are not trained to recognize sensory issues. The STAR Institute for Sensory Processing Disorder is dedicated to researching these issues, educating the public and professionals about their symptoms and treatment, advocating for those who live with Sensory Processing Disorder and sensory challenges associated with other conditions, and providing treatment. We also have a vision of a world where SPD is an accepted diagnosis, is included in diagnostic manuals such as the DSM and ICD and where treatment is covered by insurance. We will work tirelessly towards this goal.
The causes of Sensory Processing Disorder
The causes of Sensory Processing Disorder presents a pressing question for every parent of a child with SPD. Many worry that they are somehow to blame for their child's sensory issues.
Parents ask, "Is it something I did?"
The causes of SPD are among the subjects that researchers at STAR Institute for Sensory Processing Disorder and their collaborators in the SPD Scientific Work Group have been studying. Preliminary research suggests that SPD is often inherited. If so, the causes of SPD are coded into the child's genetic material. Prenatal and birth complications have also been implicated, and environmental factors may be involved. For example, children who are adopted often experience SPD, due perhaps to restrictions in their early lives or poor prenatal care. Birth risk factors may also cause SPD (low birth weight, prematurity, etc).
Of course, as with any developmental and/or behavioral disorder, the causes of SPD are likely to be the result of factors that are both genetic and environmental. Only with more research will it be possible to identify the role of each.
A preliminary summary of research into causation and prevalence is contained in Sensational Kids: Hope and Help for Children With Sensory Processing Disorder (New York: Perigee, 2014, 2nd edition).