Today, Dr. Jamie Chaves from the Center for Connection is sharing about toxic stress and sensory processing disorder. Her last guest post was so helpful in understanding how sensory processing affects kids, and we're grateful for her expertise on a related post!

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Stress is something most all of us experience to some degree on a daily basis. Stress isn’t necessarily a bad thing—it can mobilize us and allow us to function well. The good thing is our bodies and brains are designed to handle small amounts of stress. But what happens when our bodies and brains experience stress on a frequent, ongoing basis, or when stress is severe? Stress can then become “toxic stress” and it has a myriad of negative implications for the body, brain, emotions, and relationships. Examples include inattention, poor emotional control, decreased memory, difficulty learning, poor frustration tolerance, irritable bowel syndrome, and even a compromised immune system. 

In order to better understand toxic stress it’s important to understand the mechanism for a positive stress response, especially in the context of how our sensory system works. When we attend a dinner party, for example, we are bombarded with a wide variety of sensory stimuli: the hum of the air conditioner, the buzzing of conversations, the rhythm of background music, the brightness of the lights, the shininess of the silverware, the colorful variety of outfits, the smell of appetizers, the odor of perfumes, the movement of bodies around the room, the maintenance of balance in high heels, to name a few.

Our brain must integrate all of this input in order to determine the most important stimuli or information to attend to in order to socially engage and function in the situation. This requires our brainstem to receive all the sensory information from our nerves and our amygdala, and to interpret whether or not the sensory information is a threat. When the brain works the way it’s supposed to, sensory stimuli that is not important is filtered out and we gradually habituate to the hum of the air conditioner and the smell of perfume, let’s say. This is the job of the hippocampus. If someone drops a glass of wine, then our brain is heightened to that novel stimuli via the amygdala (“danger, danger!”), which causes the hypothalamus to set off a stress response. First the sympathetic nervous system kicks in, we immediately attend to the potential threat: our heart races, our breathing gets faster. We turn to assess the scenario, determine it’s not threatening via our higher cognitive cortex, and the parasympathetic nervous system kicks in to calm our brain and body back down—we can now relax, regain a regular heart rate, and continue enjoying the party (this is what Stephen Porges describes as a vagal tone).

But what happens when we cannot habituate to the unimportant sensory stimuli and/or when we remain in a heightened arousal “threat” state after the wine glass breaks? This is what happens with sensory overresponsiveness (SOR), a subtype of sensory processing disorder, and what can lead to toxic stress levels. Studies have found that children with SOR have a higher sympathetic response (faster breathing and heart rate, more muscle tension, feelings of panic or anxiety) and have a delayed/lower parasympathetic calming response (i.e. they have poor vagal tone) to incoming sensory information. This means that children with SOR experience a stress response on a more frequent and more intense basis. And, they can remain in elevated states of stress for longer periods of time than neurotypical children. These studies also indicate that children with SOR take longer than their neurotypical peers to habituate or get used to the same stimuli over time, so their threat response systems get activated each time they’re back in that situation. After several exposures to those negative situations the brain begins to anticipate the threat, thereby heightening the stress response even more. They cannot be “talked through” the situation or “reasoned with” because access to the higher, thinking, cognitive cortex has been blocked by the stress response.

Because it is impossible to control all sensory-related aspects of the environment, children with SOR can present as highly anxious, controlling, withdrawing, or with acting out behaviors-- all of which are responses to repeated, elevated stress. Other signs of stress-invoked SOR include: sweating, disorganization, wide eyes, heavy breathing, irritability, uncontrollable laughter, poor frustration tolerance, and aggressiveness. It is notable that the vagus nerve connects not only to the heart and lungs (think about how your heart rate and breathing change when you are under stress) but also to the digestive system. It is not surprising, therefore, that many children with SOR experience problems with their gastrointestinal systems, such as constipation, nausea, diarrhea, and bloating. Their bodies are crying out for relief.

The good news is that many sensory-based therapeutic interventions target activation of and strengthening of the vagal nerve in order to calm the parasympathetic (calming) nervous system and increase habituation to sensory stimuli. Some of these include therapressure brushing (a.k.a Wilbarger Brushing), listening programs (Integrated Listening System, Tomatis Method), and rhythmical swinging activities, among others. Children must be in a state of regulation, or optimal arousal, or what we can call “tolerable stress” before they have the capacity to learn, develop new skills, and try novel activities.

The primary goals of a skilled occupational therapist in a session are 1) to regulate the child if he/she is dysregulated (in other words, get their nervous system in balance where the threat systems can be quieted), 2) maintain an optimal state of regulation throughout the session (increasing vagal tone), and 3) present “just right” sensorimotor challenges to the regulated child (which allows the child to expand what their nervous systems can tolerate, changing previously “threatening” stimuli into tolerable stress).

Because I operate through a Sensory Integration lens, I achieve these three goals through the use of sensory-based mediums and therapeutic tools so that over time, the brain experiences less stress less intensely and less often, is less reactive to sensory information, and is better able to integrate multiple sensory stimuli in a meaningful way. When this happens the child can happily attend the aforementioned dinner party without fearing that someone will drop a glass, or brush up against them, or wear too much cologne, for example—their stress response will match the situation. Changing the way the neurological system responds to incoming sensory stimuli, however, takes time—usually 6-12 months of ongoing therapy. In the meantime, it is important that parents, educators, relatives, and other professionals recognize that acting out behaviors may actually be a sensory-related stress response, and the child may need support, soothing through co-regulation, and intervention instead of behavioral interventions or punitive responses. Caregivers and professions can also be more aware of scenarios that cause stress in children with sensory overresponsiveness and take steps to decrease the intensity of those sensory experiences to prevent a toxic stress load. 

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Dr. Jamie Chaves, OTD, OTR/L, SWC is a pediatric occupational therapist at The Center for Connection in Pasadena, CA. She also holds a California feeding and swallowing certification. The Center for Connection, founded by Dr. Tina Payne Bryson (author of The Whole Brain Child and No Drama Discipline is an interdisciplinary center that promotes health and happiness through a relationship-based perspective. For more information visit us online at: www.thecenterforconnection.org.