ADVICE ON MENTAL HEALTH: Sensory Over-response and Anxiety in Children With and Without Autism
ADVICE ON MENTAL HEALTH - from Brain & Behavior Magazine, September 2021 issue
Q&A with Kimberly L. H. Carpenter, Ph.D.
Duke University School of Medicine
Assistant Professor in Psychiatry and Behavioral Sciences
Assistant Research Professor in the Social Science Research Institute
2015 BBRF Young Investigator Grant
As researchers move closer to developing useful interventions for children at risk for anxiety before a fullblown anxiety disorder appears, one important objective is to identify factors or traits very early in life that correlate with elevated risk. Dr. Carpenter and colleagues may have found one such factor: sensory over-sensitivity. In one study, published in the Journal of Abnormal Child Psychology, they examined over 900 children aged 2 to 5, 191 of whom were re-examined at age 6. They found that preschoolers with overly sensitive senses—who are intensely bothered by loud or high-pitched sounds, for instance, or the sensation of clothing rubbing on the skin, or bright lights—are at greater risk for developing an anxiety disorder by school age. In this Q&A Dr. Carpenter discusses these and related findings, including those probing the relationship between early sensory over-responsivity and the risk for developing anxiety in children with autism spectrum disorder.
Dr. Carpenter, before we discuss the relationships you have identified between sensory overresponse, early anxiety symptoms, and autism spectrum disorder (ASD), we’d like you to set the stage and talk first about anxiety disorders in young people. How prevalent are they?
Anxiety disorders are quite common in young children. About one in five preschool-aged children meet the criteria for an anxiety disorder. Furthermore, data from an important sample of children drawn from the general population that has followed them across the years—the Great Smoky Mountain Study—suggests that anxiety disorders are present across early childhood and adolescence.
The Great Smoky Mountain Study started at Duke University in the early 1990s to examine the prevalence and development of childhood psychiatric disorders using a sample of over 1,400 children who were recruited from rural counties in Western North Carolina.
To think that as many as one in five of these young people meet criteria for an impairing anxiety disorder by the time they are 26 tells you that this is a highly prevalent and early-emerging problem.
Anxiety disorders also increase the risk of lifelong difficulties with mood disorders. In fact, as data from the Great Smoky Mountain Study indicates, adolescent anxiety is associated with 2.8 times greater odds of having anxiety as an adult and 1.85 times greater odds of having depression in adulthood. [Editor’s note: this historic study was initially organized and directed by epidemiologist and 2007 BBRF Distinguished Investigator E. Jane Costello, Ph.D., and her husband, Adrian Angold, M.D., who in 2009 were awarded BBRF’s Ruane Prize for Outstanding Research in Child and Adolescent Psychiatric Research.]
You say the prevalence of anxiety in children without autism is about 19% to 20%. What about in children who are diagnosed with autism?
In children with autism, the rate of anxiety is double that. One study shows that approximately 40% of all children with autism meet criteria for an impairing anxiety disorder. The problem is that despite the early emergence of anxiety symptoms and the long-term impacts on the lives of individuals with autism, many current interventions focus on alleviating anxiety symptoms in older children and adults who already suffer from an anxiety disorder.
The issue is that by the time most children receive these treatments, they’ve already developed a number of co-occurring challenges, including difficulties with sleep, recurrent stomach aches, and increased irritability. In addition to this, co-occurring anxiety has also been linked to increased core autism symptoms, including more difficulties with social interactions and more repetitive behaviors.
In order to prevent the significant impairment that results from anxiety, an ideal intervention would happen before fullblown anxiety emerges. The goal of such a strategy would be to reduce or prevent the onset of both the anxiety symptoms and the associated co-occurring challenges that I mentioned, rather than treat them after they’ve already become impairing.
Importantly, your research has identified hyperactive senses in preschoolers as a potential predictor of anxiety. We understand that you have studied this both in children who don’t go on to develop autism as well as in children who do.
In general, we’ve found that one potential risk factor for anxiety in children with autism is sensory over-responsivity, characterized by heightened and unusual reactions to everyday sensory stimuli. Just about every aspect of our lives is driven by how our senses perceive our environment. Right now, I hope that readers’ primary sensory input is the words they are reading on this page. They are probably not paying attention to the sound of the air conditioning or the feel of the tag of their shirt. But imagine if you weren’t able to filter out that non-essential sensory information. That would be really hard, right? Well, this is what happens in about 56% of individuals who have autism.
What’s even more striking is that sensory challenges are also one of the earliest and most persistent concerns reported by parents of children who go on to develop autism.
How could these early sensory challenges contribute to the high rates of anxiety in children with autism?
Imagine that instead of just being a nuisance that you can’t ignore, a sensory experience actually causes you distress. Say you have a young boy, Tommy. Tommy’s out to dinner with his parents and he needs to use the restroom. Just as he walks in to the restroom, someone activates the automatic hand dryer. Now, unfortunately for Tommy, the sound causes his sensory system to react in a way that’s similar to how I react when someone scrapes their nails on a chalkboard. Perhaps he will throw his hands over his ears. Perhaps he will run straight out of that restroom. Now, imagine that the following week, Tommy goes to the mall with his mom, and he again needs to use the restroom. Just as before, someone is using the automatic hand dryer as Tommy walks in.
At this point, Tommy’s brain has made a very clear connection between the sound of the hand dryer and the public restroom. His brain is wired to be over-reactive to these experiences. Tommy has learned that in order to not have these negative sensory experiences, it’s best he just avoids public bathrooms altogether, which he begins to do. This becomes a significant problem for both him and his family because they can no longer be away from home for extended periods of time. If they do find themselves away from home and Tommy has to go to the bathroom and they try to make him, he ends up resisting. A situation like this can cause the family to avoid leaving the house with Tommy unless it’s absolutely necessary. You can see how this can very quickly become impairing for a family.
In other situations, everyday noises like a car horn or a lawnmower can cause distress. In such cases, the unpredictability of these sounds may cause these individuals to remain in a constant state of hyper-arousal and hyper-vigilance so that they are prepared to react the instant that they encounter any one of these negative sensory experiences.
This is in contrast, I take it, to the more predictable experience in the hand dryer example, where the predictability of the sound led Tommy to avoidance and phobia of bathrooms.
Right. And these two kinds of cases have led researchers in the field to suggest that these are two possible ways that sensory over-responsivity could lead an individual to develop an anxiety disorder. Our own group has found a positive relationship between sensory over-responsivity and anxiety symptoms in a study of 69 children with autism, ages 3 to 6. This replicates previous findings from a number of other research groups.
The next question is whether sensory over-responsivity is related to all kinds of anxiety or only to certain subtypes. In our study, we found that children with autism who had the greatest levels of sensory over-responsivity were 22 times more likely to meet criteria for generalized anxiety disorder and 10 times more likely to meet criteria for separation anxiety. Again, this replicates what others have found.
Together, our data and that of others suggest that there’s a clear connection between sensory over-responsivity and anxiety in preschool-aged children with autism. But: it also suggests that there’s more to the story, since not all children with co-occurring autism and anxiety also have sensory-over-responsivity.
In light of this, how do you think sensory overresponsivity and anxiety are linked—in children with autism and in children without autism?
In children with autism, it could be that sensory overresponsivity precedes anxiety, or it could be that sensory over-responsivity is an early manifestation of anxiety. Without longitudinal data, i.e., data that follows children over a period of years, it’s impossible to know which of these is the case.
Luckily, other researchers have been able to explore this in a longitudinal sample of children with autism. In the first study that I’m aware of to explore the temporal relationship between sensory over-responsivity and anxiety, researchers recruited a sample of young children with autism and measured their sensory over-responsivity and their anxiety when they were between 18 and 33 months of age, and then again, one year later.
Through this analysis, they were able to demonstrate that sensory over-responsivity predicts changes in anxiety over the period of toddlerhood. They did not, however, find the opposite to be the case. By this I mean that when children in the study had anxiety at a certain point in their development, the researchers did not find that this predicted that they’d develop sensory over-responsivity at some future time.
This supports the idea that sensory over-responsivity often does precede anxiety symptoms, at least in children with autism—but does not necessarily predict it.
What about children who don’t have autism?
That’s an important question, we think, because understanding this could have important implications for how one might approach treatment. If the pattern is the same, regardless of whether a child has autism or not, then the same treatment approaches may be applicable across individuals.
My colleagues and I set out to explore whether the same relationship between sensory over-responsivity and anxiety was true in 917 children who were recruited from three Duke pediatric primary care clinics (they were part of the Duke Preschool Well-Being Study). With this incredible sample, we were able to first explore baseline rates of sensory overresponsivity in a relatively large sample of preschool children drawn from the general population.
We found that 20.5% of our sample met criteria for at least one sensory over-responsivity during the preschool period. OK, then: how does sensory over-responsivity relate to anxiety in our sample? We found that, in this sample, 43% of children with sensory over-responsivity met criteria for at least one impairing anxiety disorder during the preschool period.
Luckily, a sub-sample of 191 of those 917 children returned to our lab a few years later to take part in a follow-up study, the Learning About the Developing Brain study, and we were able to obtain the same measurements that we did in their first visit. This allowed us to ask the question: if a child has at least one symptom of sensory over-responsivity when they are between 2 and 5 years old, are they more likely to meet criteria for an impairing anxiety disorder when they reached school-age?
We concluded that the answer to this is yes: sensory overresponsivity in the preschool period significantly and positively predicted anxiety symptoms at age 6 in children who were not diagnosed with ASD. Furthermore, this relationship was specific for anxiety disorders after accounting for other disorders that the children may have, such as ADHD.
Just as we saw in the children with autism, the opposite was not the case. Anxiety in the preschool period did not predict later symptoms of sensory over-responsivity.
So, to be very clear: this research led us to conclude that having at least one sensory over-responsivity as a preschooler is specifically associated with increased risk of having an anxiety disorder at 6 years old.
We know that some of your research focuses on neuroscience—about what may be going on in the brain to cause problems like sensory over-responsivity.
Yes. My lab has been looking at the question of how all of this relates to brain function. If we can start to understand the neurobiology of this relationship, we may be able to identify biologically relevant markers for these difficulties that could help us identify, for example, which children are most likely to respond to a particular treatment.
Or we may be able to identify biological endpoints that we can then use in clinical trials to track the success of treatment. If we understand the underlying neurocircuitry of sensory overresponsivity and anxiety, and how it affects different individuals, we may even be able to use that information to help us individualize treatments.
The way in which the brain processes potentially threatening stimuli is actually pretty well understood. Let me introduce you to my two favorite brain regions. First is the amygdala. The amygdala plays a critical role in driving our reactions to stimuli. Say, for example, you’re walking along a trail and you see something that could be a snake. Your amygdala sounds the alarm that there is a potential danger and sets off the fight-or-flight response.
My second favorite region is the prefrontal cortex. What happens if you realize that you did not actually see a snake, but instead, just a coiled-up rope? Well, the prefrontal cortex plays a role in telling your amygdala that, and helps it put the brakes on that fight-or-flight response.
When the delicate balance between the prefrontal cortex and the amygdala gets disrupted, you move away from what we call adaptive anxiety—the kind of helpful anxiety that is warranted by, say, a dangerous or risky situation—and toward unchecked anxiety, which can lead to both hyper-vigilance and avoidance.
Is this similar to what may be happening in the brain of individuals with both sensory over-responsivity and anxiety?
Yes. As part of the follow-up to the Duke Learning About the Developing Brain Study, we had 83 children return to receive a functional MRI scan. We looked at how their brains processed faces depicting different emotions. We found that children who met the criteria for an anxiety disorder during the preschool period were more likely to have decreased connectivity between the amygdala and the prefrontal cortex at age 6, the time they enter elementary school.
These same brain networks have also been implicated in sensory over-responsivity. This was one result of a recent study that looked at the functional brain response to sensory stimuli in children with autism, some of whom had sensory overresponsivity and some who did not have it.
The prefrontal cortex in children without sensory overresponsivity did a great job in dampening the response of the amygdala. However, the children with sensory over-responsivity had decreased connectivity between the prefrontal cortex and the amygdala, somewhat similar to what we found in our anxious preschoolers in whom the prefrontal cortex was not doing its job in putting the brakes on the amygdala.
What use can be made of these discoveries? How do you proceed from them?
Think about the brain being like your muscles. Just like you can do some bench presses to try to increase the strength of your chest muscles, there’s evidence that therapies for anxiety can strengthen the connections between the prefrontal cortex and the amygdala.
For example, take cognitive behavioral therapy, or CBT, which is a common intervention for treating anxiety, and which has been demonstrated to significantly decrease anxiety symptoms in children with autism.
Now, CBT has two primary components that are affecting different aspects of brain function. The first is the cognitive part, which focuses on changing the thought patterns responsible for negative emotional and behavioral patterns. The second aspect is the behavioral therapy piece, which includes things like exposure to the stimuli that are causing anxiety, and includes helping the individual learn effective behaviors to replace their ineffective behavioral responses. These different components of CBT are basically training the prefrontal cortex to put the brakes on an overactive amygdala.
An MRI study of the brain in adults with social anxiety who improved after CBT demonstrated that the improvement was associated with increased plasticity in the amygdala. Plasticity refers to the ability of neurons to change the strength of their connections.
There are also newly emerging therapies that target executive functions, which are skills and processes that enable us to plan, or to focus our attention to achieve our goals. What’s important to know about executive functions is that the prefrontal cortex plays a critical role in driving them. Differences in executive function are implicated across a number of disorders, including both autism and anxiety.
Can you give us an example?
For example, both children and adults with anxiety often present with a bias toward focusing on negative information in their environment over and above positive information. Specifically, threatening cues tend to capture the attention of individuals with anxiety. Once captured, they then have difficulty disengaging their attention away from that negative information. So, researchers have developed a treatment that aims to teach the brain to more flexibly shift attention away from threatening information.
It’s called attention bias modification training or ABMT, and it’s been shown to be effective for treating anxiety in children. Just like with CBT, the amygdala appears to play a role in driving this efficacy in treatment of anxiety.
Based on all of the findings you’ve shared, can you give us a picture of how they might help children and their parents in a clinical setting?
If we can identify children who struggle with sensory overresponsivity before they go on to develop an anxiety disorder and have a psychologist, occupational therapist, or other clinicians work with them to help them practice engaging that prefrontal cortex and decreasing the response to their amygdala when they experience negative sensory stimuli, then it is possible that we can help some children from progressing from sensory over-responsivity to a full-blown anxiety disorder.
What should a parent do if their child is experiencing sensory over-responsivity?
I think the first thing to do is always talk to your pediatrician. But I think if you’re very concerned, please keep in mind that there are occupational therapists out there who specifically focus on this. It might make sense to find an occupational therapist or a psychologist to help you and help your child work through these issues so that they don’t become an impairing problem, or don’t evolve into one.
What should a parent do if they see that their child is experiencing significant anxiety at a young age or a little older in adolescence?
If you’re worried, I always say, please seek help. Talk to your pediatrician, find a good child psychologist, find an occupational therapist. These people are amazing at what they do, and they know what they’re doing.
Written By Fatima Bhojani and Peter Tarr, Ph.D.