An Overlooked Population: Adults with Sensory Modulation Disorder

Jessma Barrani

University of Utah


This paper brings to light the physical, emotional, and social difficulties experienced by children and adults with Sensory Modulation Disorder (SMD). SMD is a subtype of Sensory Processing Disorder (SPD). SPD is a condition in which a person's perception and their responses of sensory stimulation are atypical to the stimulus (Miller & Benjamin, 2013). Sensory modulation disorder is defined as difficulty modulating and regulating the degree, intensity, and nature of responses to sensory input. Their uncharacteristic response prevents them from adapting to the demand of everyday life (Kinnealey, Koenig, & Smith, 2011, p. 320).

Most people have occasional problems processing sensory information. For children and adults with SMD, problems with sensory processing are chronic and disruptive to everyday life. Extensive research has been conducted on children with SMD. Very little research has been conducted on Adults with SMD. As SMD is a life long disorder without a cure, it is puzzling that there is such a lack of research on adults with Sensory Modulation Disorder. There needs to be more research focused on adults with SMD.


A teacher is frustrated at students who jump up and down in their seats, do not participate or interact with other students, are slow to respond to their names, and don't recognize social cues. For some students that fit this profile, the issue is purely behavioral, but for other students the root of the problem is the way they process messages. Sensory Processing is a term used to describe the way the nervous system receives messages from the senses, decides what the messages are, and then responds. Children and adults with Sensory Modulation Disorder (SMD) struggle with receiving, integrating, and responding to messages. They are often misunderstood, misdiagnosed, and mislabeled by doctors, professionals, and even their own family members.

SMD is a subtype of a larger processing disorder known as Sensory Processing Disorder (SPD). This is a condition in which a person's perception and response to sensory stimulation are uncharacteristic and different from most people's response. An example is walking on grass barefoot, an experience that is painless and tolerable to most people. To a person with SPD, it might feel like stepping on needles or it may even feel unbearably slimy.

Neurologically, it's like a traffic jam that inhibits certain parts of the brain from receiving the information needed to appropriately integrate sensory information (Miller & Benjamin, 2013). People with SPD encounter difficulties in everyday life experiences from brushing their teeth to embracing a hug. SPD is observable by motor clumsiness, behavioral problems, anxiety, depression, academic difficulties, and problems of coping during social situations.  

SMD displays similar traits, but as Miller and Benjamin (2013) explained, people who suffer from SMD experience difficulties "modulating and regulating the degree, intensity, and nature of responses to sensory input" in a way that is consistent with the situational demand. Sensory processing disorders are as common as attention deficit hyperactivity disorder (ADHD) yet receive far less attention because it is not recognized as a distinct disease (Bumin, 2013).  As a conservative estimate, 5 percent of school age children, one in every twenty, have a form of SMD, (Kinnealey, Koenig, Smith, 2011, p. 321). This study estimated that the percentage is similar in adults. Individuals with SMD experience everyday life very differently than others.

One of the best ways to demonstrate the differences in reactions from a child with SMD to a child without SMD is to compare how they react to the same situation. Kranowitz (2005), in her book "The Out of Sync Child," conducted such an experiment with two seven year old girls playing the same game of jacks. She recorded how the two girls reacted to the situation. Her illustration is very useful because she pinpoints typical red flags of SMD.

Susie, a child without SMD, is at recess on a cold day playing jacks. The cement she is sitting on is cold, but she ignores it because she is interested in the game. She is not playing as well as usual because her hands are so cold. The first time her hand fails to scoop up the jacks, she is disappointed but continues playing. The second time, she is more frustrated. The third time, she decides to jump rope instead to warm up her body (Kranowitz, 2005, p. 58).

Placed into the same situation, Mary, a child with SMD can't concentrate because the cold cement is too distracting. On her first two turns, Mary struggles to scoop the jacks. On her third try, Mary's hands are too stiff. Suddenly Mary explodes, kicking the jacks, and screaming, "I hate jacks!" She begins to cry uncontrollably and stays upset for the rest of the morning. Mary is so distressed all morning she cannot focus on her school work (Kranowitz, 2005, p. 58).

The first red flag is the extreme difficulty Mary had mentally blocking out the cold cement. Second was in her fine motor movement, from the very beginning Mary had trouble coordinating the movement. The third major red flag is how Mary could not socially regulate her emotional frustration; instead she exploded. The fourth major red flag is how her emotional stress lasted for hours, instead of minutes. Most adults with SMD have encountered similar situations and have learned to develop coping mechanisms such as avoidance, mental preparation, talk through, and confrontation to deal with such situations (Kinnealey, Oliver, Wilbarger, 1995).

As illustrated in the experiment above, people with SMD have very hard time adjusting to their environment. It manifests itself emotionally, socially, and physically. Extensive research has been conducted on the neurological underpinning and the effectiveness in therapeutic techniques used in treatment in children with SMD. Very little research has been conducted on adults with SMD.  Because SMD is a disorder that has no cure and is pervasive, it is disconcerting that there is a lack of research conducted on adults with SMD.

Understanding SMD

It is important to understand that our senses give us essential information about the surrounding environment. People with SMD do not receive accurate information from their senses. The human body has seven senses including sight, smell, sound, taste, tactile, vestibular, and proprioception (Bod, Gough, Home, & Mopnique, 2013). The last three mentioned are often overlooked and need further explanation.

Tactile senses give information from the skin about temperature, pressure, texture, touch, pain, and movement. Vestibular senses give information about where our body is in relationship to gravity. It contributes to posture, balance, and eye movement. The body's proprioceptive senses are similar to a mental body map of the positioning and movement of muscles and joints. All sensory receptors and processors are housed within the nervous system (Bod, Gough, Home, & Mopnique, 2013).

Individuals with SMD perceive and respond to sensations differently because of the way their nervous system modulates sensory information. Sensory modulation refers to the brain's "ability to respond appropriately to the sensory environment and to remain at the appropriate level of arousal or alertness" (Wild, 2013). A simple example of sensory modulation is the ability to tune out the noise of a crowd and listen to a friend. The brain acknowledges the presence of the crowd and the sound but adapts by redirecting the focus to the conversation with a friend. A person with SMD may not be able to do this. Instead he/she may become overwhelmed by the noise and become frustrated, angry, and want to leave. Modulation helps us self-regulate and be selective of what we cognitively sense.

There are three subtypes within SMD: over-responsive, under-responsive, and sensory seeking. Over-responsive is an exaggerated response to sensory input. These individuals are receiving too much sensory input. They may be overwhelmed by busy environments, have problems with tags and seams in their clothes, and have a low frustration tolerance. Under-responsive refers to a lacking of response to sensory input. They do not get enough information about their environment and may seem tuned out. Sensory seeking individuals need extreme input for the sensation to register properly. These people have a very difficult time staying still and may seem to want to touch everything. Sensory seeking children will often crash into walls on purpose to get that extra input (Wild, 2013). It's important to remember most people experience symptoms similar to the symptoms described above within their lives. Yet these symptoms for a person with SMD are chronic and life disruptive to everyday life.

Emotional and Social Experiences

The emotions of people with SMD are not only caused by the discomfort of the sensory stimuli but also social situations surrounding them. Children and adults with SMD are often unable to meet social expectations and in turn experience high feelings of inadequacy and low self-esteem. These feelings translate into coping patterns of conflict and/or isolation at home, work, or school. Anxiety and depression are strongly linked to SMD (Kinnealey & Pfeiffer, 2003; Kinnealey, Koeing, & Smith, 2011; Kinnealey, Oliver, & Wilbarger, 1995; Dunn, 2011). In both children and adults social relationships and activities are greatly compromised due to their difficulty regulating their response to sensory stimuli.


Emotional deregulation and outbursts are the most challenging aspect of SMD for both the child and the parent (Kranowitz, 2005, p. 261).  The degree and frequency of emotional outbursts directly affect individuals' participation in social life. To look deeper into the social participation patterns of children who suffer from sensory processing difficulties, Cosbey, Johnston, and Dunn (2010) compared social participation patterns of children with SPD and without SPD ages 6-9 years old.  In areas of enjoyment both groups scored very similar. However, in categories involving diverse social networks children with SPD scored significantly lower than their peer without SPD. Cosbey, Johnston, and Dunn (2010) reported that "most of their social activities took place with immediate family [members] or alone" (p. 470). The findings suggest that children with SPD do not get the same opportunities to develop social skills necessary in building and maintaining social relationships. Social skills learned in childhood include but are not limited to "the abilit[y] to comfort, share, help, and cooperate [and] learn conflict resolution" (p. 462). This conclusion of isolation and limited social networks can be applied to children with SMD because of the overlapping symptoms seen in both SPD and SMD. Isolation and limited friendship is a disadvantage that affects adulthood as childhood is the time we learn social skills fundamental to healthy meaningful adult relationships.


Emotional and social patterns of children with SMD found by Cosbey, Johnston, & Dunn (2010) are similar to those of adults. Researchers Kinnealey, Koenig, and Smith (2011) described adults with SMD as having perceived a "daily experience as [being] irritating, overwhelming, disorganizing, and distracting" (p. 320).  Even though the emotional collision adults experience is rooted in the way in which they perceive stimuli, adults with SMD are more often referred to a mental health professional (Dunn, 2011).

Adults with SMD have a significantly high correlation with mental health issues such as "anxiety, depression, social-emotional issues, autonomic nervous system reactivity, and coping strategies [that are not socially expected]" (Kinnealey, Koenig, & Smith, 2011, p. 320). Research by these same researchers to investigate the mental health of adults with SMD ages 18 to 46 found that "anxiety and was inversely correlated with social supports" (p. 324). Thus, individuals with higher symptoms of anxiety perceive themselves to have less social support. Social support is powerful factor in coping with stress and developing emotional resiliency (p. 320). The authors supported the claims of previous studies conducted by Dunn (2011) and Kinnealey, Oliver, & Wilbarger (1995) that found those with more social support were better able to regulate their emotional responses and better adjust to demands of life.

Often adults will exert an excessive amount of time coping with their sensory defensiveness. Kinnealey, Koenig, and Smith (2011) found that "a situation that leaves them feeling exhausted and frequently isolated" (p. 320; Kinnealey, Oliver, & Wilbarger, 1995). To reduce the occurrence and/or the overall impact of environmental stimuli, adults develop coping mechanism—a behavior which has been observed and reported by numerous occupational therapists and mental health professionals.

Kinnealey, Oliver, & Wilbarger (1995) further explored the subjective experiences of coping mechanisms in adults with SMD. The study identified six coping mechanisms: avoidance, predictability, mental preparation, talk through, counteraction, and confrontation (p. 444). The coping mechanisms observed and identified are both emotional and socially taxing. The researchers concluded that coping mechanisms drastically "influenced their choices of activities" and opportunities for social interaction (p. 451). Social relationships and leisure activities have been identified as central components to an individual's quality of life by the World Health Organization (Cosbey, Dunn, & Johnston, 2010, p. 320). People with SMD may experience a significantly lower quality of life because of the sensory confines of his/her disability.

Limited research has been conducted on the long-term effects of living with such coping mechanisms and the effect on occupation or intimate relationships. High feelings of anxiety, depression, and social isolation have been studied and agreed upon by numerous occupational therapists and health professionals (Kinnealey & Pfeiffer, 2003; Kinnealey, Koenig, & Smith, 2011; Kinnealey, Oliver, & Wilbarger, 1995; Dunn, 2011). The underlying pitfall toward making real improvements in treating Adults with SMD the need to validating the disease by using technology to prove physiological and neurological biomarkers of SMD in adults.


Children with a SMD diagnosis look from the outside as being "normal' and so do adults. SMD is considered to be an invisible disability, meaning it is not apparent by appearance or the way in which someone walks or speaks. For this reason, technological biomarkers are very important to prove the legitimacy of SMD to the medical community. There have been several important studies using technology to establish physiological and neurological biomarkers in children diagnosed with SMD and SPD.


The most recent and promising research was conducted by child neurologist Marco and Owen, a postdoctoral scholar in radiology and biomedical imaging. Using an advanced form of an MIR, researchers discovered abnormal white matter tracts in areas involving tactile, visual, and auditory sensory processing. The abnormal white matter found in children with SPD "correlates directly with the atypical sensory behavior" that is pervasive and chronic in both SPD and SMD (Owen, Marco, Desai, Fourie, Harris, Hills, Arnett, & Mukherjee, 2013).

White matter insulates neural tissue to make neural processing faster and more efficient. The white matter tracts responsible for processing the seven senses are among the fastest signals conducted within the brain (Ingebretsen, 2013, p. 47). Children with SPD and SMD either have too much or too little insulation in different sensory processing areas. This gives scientific reasoning to the reason the population has spectrum characteristic, on one end extreme sensitivity and the other what appears to be numbness to sensation. Owen et al. (2013) finished their research by clearly stating, "from a clinical perspective, these findings suggest that children with SPD have a specific imaging biomarker for their clinical disorder and the pattern of their shared structural difference" (n. pag).  This study established biomarkers SMD and SPD and as a result validates the disease itself.

Another benchmark study by Schaaf et al. (2010) evaluated activity patterns within the autonomic nervous system of children diagnosed with SMD. To understand the study, it's important to understand the basic parts of the nervous system. The autonomic nervous system is the control center for all the unconscious functions in the body, which control all organs, movement, emotions, and thought patterns. The autonomic nervous system is then split into distinct branches, the sympathetic and parasympathetic. The branches are connected in a teeter tooter fashion, when one branch's activity goes up the other goes down. Schaaf et al. (2010) focused on the activity of these branches. The role of the sympathetic branch is to defend the body by causing emotional and biological defense responses such as fear, anxiety, and increased heart rate. The job of the parasympathetic branch is to seek and maintain a stable state, in which the body adapts to the external environment (Ingebretsen, 2013, p. 43). Now that the basics are covered we can evaluate the study.

Researchers found, "children with the most severe SMD demonstrate significantly lower baseline parasympathetic functions" and as a result high sympathetic functions (Schaaf et al., 2010). This means the body biologically does not adapt and self-regulate the response to the environment, such as a busy crowd. Most people can ignore the busy crowd and adjust to the environment. Those with an impaired parasympathetic function cannot grade or regulate their response to the crowd and become overwhelmed. They also experience anxiety and fear and exhibit defense responses of the sympathetic branch. The researchers added that the parasympathetic nervous system also plays an important role in the "recovery from a stressor[s]/challenge[s]" (Schaaf et al., 2010).  This, too, biologically supports the reason stress lasts hours instead of minutes for children with SMD.


Owen et al. (2013) validate the structural differences within the brain of children with SMD, while Schaaf et al. (2010) proved the neurological impairment of adapting to their environment. These two studies validate the significance of the disorder in children but completely neglect the adult population with SMD. Structurally, both a child's brain and an adult's brain have designated areas for sensory processing. But clinicians cannot assume this study validates an adult's diagnosis with SPD or SMD. These two study methods must be conducted on adults with SMD—not only validate the disease but to have biological biomarkers to diagnose and measure the biological impact of the disease.


Occupational therapists have developed a treatment method known as sensory integration to treat both children and adults with sensory processing disorders. Sensory Integration (SI) is based upon two capabilities of the brain modulation and neuroplasticity. As discussed earlier, modulation is the brain's ability to selectively filter stimuli, a functional impairment in SMD. Neuroplasticity refers to the brain's lifelong ability to reorganize itself by creating new neural connections (Ingebretsen, 2013, p. 46).

Occupational therapists combine sensory experiences that are familiar, relaxing, and challenging for a person's individual sensory needs into one treatment session. This combination is called a prescribed sensory diet. It literally feeds the senses in area that are both deficient and healthy by experiencing senses. The sensory diet uses the brain's neuroplasticity to mend sensory processing areas found by Owen et al. (2013) to be structurally abnormal in the brains of children with SPD. By building new neural connections in sensory processing areas, the brain's ability to modulate stimuli is directly affected. It's very important for the occupational therapist to find specific sensations like rocking in a rocking chair to relax the nervous system and counteract the anxiety from aversive stimuli. As found by Schaaf et al. (2010), the anxiety children with SMD feel is a result of the increased sympathetic activity in the nervous system. Sensory Integration has been used with children for over forty years, far before any studies proved the scientific basis for sensory processing disorders.


Occupational therapists use play and stories to integrate familiar, relaxing, and challenging sensory stimuli. Miller, Coll, and Schoen (2007) carried out a randomized control trial on twenty-four children with SMD. Interventions were twice a week and lasted ten weeks. Children in the sensory integration group showed a considerable decrease in sensory defensiveness after the ten weeks. Researchers claimed "this finding suggests that [Occupational Therapy-Sensory Integration] may be effective in ameliorating difficulties of children with SMD" (Miller, Coll, & Schoen, 2007 p. 232). Much of the research was conducted with small sample sizes, making the effectiveness questionable to many physicians. Pediatricians Zimmerman and Desch (2012) expressed the need for parents to be aware of the lack of research in sensory integration and the controversy of regarding efficacy.


As is in children, research on the effectiveness of sensory integration in adults is more limited. Given that studies have shown the correlation between SMD and anxiety, researchers Kinnealey and Pfeiffer (2003) conducted a study to explore the effects sensory integration on both anxiety and sensory defensiveness. Fifteen adults diagnosed with SMD and high levels of anxiety participated. Occupational therapists prescribed individualized daily sensory diets to each participant. They compared levels of sensory defensiveness and anxiety before and after the one month of treatment. Results indicated that both levels of anxiety and sensory defensiveness levels decrease in one month of sensory integration treatment. The results supported the Kinnealey and Pfeiffer (2003) hypothesis of the "significant relationship between defensiveness and anxiety" (p. 183; Kinnealey, Koeing, & Smith, 2011; Kinnealey, Oliver, & Wilbarger, 1995; Dunn, 2011). The Kinnealey and Pfeiffer (2003) study and other case studies show there is promise in treating adults with a prescribed sensory integration diet. Nevertheless, before sensory integration is viewed as a justifiable form of treatment, more research must conducted on its efficacy.

Integrating Research

Within the last ten years research studies conducted by neurologists have supported many studies that have been conducted and clinically observed by occupational therapists and healthcare professionals. Owen et al. (2013) breakthrough study detecting abnormal white matter provides tangible scientific reasoning of why children and adults with SMD exhibit a spectrum of sensory difficulties. Schaaf et al. (2010) findings of increased sympathetic function in children with SMD support Kinnealey and Pfeiffer (2003) and Kinnealey, Koenig, & Smith (2011) research by neurologically proving why SMD and anxiety have a significant correlation. Anxiety is a byproduct of heightened sympathetic function. Detection by Schaaf et al. (2010) of decreased parasympathetic function with SMD supports the reason children with SMD have such a hard time self-regulating their response to environmental stimuli. It also gives reasoning for this population's emotional stress that lasts hours instead of minutes. The studies support each other and also reveal the reason SMD is a chronic and debilitating disease.

Given that the brain is structurally impaired, circuits are causing the defensive reactions. When a defense reaction takes place sympathetic activity increases, parasympathetic activity decreases, and emotional processing areas are affected (Kinnealey & Pfeiffer, 2003, p. 183). Once sympathetic activity is high, sensations like sound and touch are much more profound and feelings of anxiety increase. Because parasympathetic activity is low, the ability to tune a sound out is impaired, and it is more difficult to ignore. The anxiety and persistent strong stimulus causes stress to last a long time, and it is difficult to relax. This series of daily events is debilitating and of a circular nature. It not only affects one person's quality of life, but it is biologically dangerous for long periods of time.

Prolonged periods of stress are strongly associated with developing secondary conditions and lifelong diseases. Studies have shown that people with increased sympathetic functions are at a higher risk of developing autoimmune disease, fibromyalgia, chronic headaches, migraines, and other genetic diseases (Ingebretsen, 2013, p. 56). These conditions and diseases are not only challenging to treat but often have no cure. It's baffling that researchers have neglected adults with SMD, a population that experiences extreme stress daily.

It's crucial that technological imaging and parasympathetic/sympathetic analysis be conducted on adults with SMD. More research needs to be conducted on the efficacy of sensory integration with adults. This population's quality of life is already compromised; with the additional likelihood of developing another chronic condition, it is puzzling that more research has not been conducted on adults. The population of adults with SMD can no longer be overlooked.


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