Understanding autistic anxiety

This blog post will summarise some of the research articles I have read recently around some proposed mechanisms of anxiety in an autistic person.

I'm autistic and have always experienced anxiety in some form, for as long as I can remember. I once explained it to a therapist as "never feeling safe" in my body, like I was always under threat. They didn't quite understand what I meant, but after my own research I've started to understand it a little bit more.

A good place to start was South and Rodgers, 2017. They looked at three contributors to anxiety in the autistic person, that had shown consistently to correlate positively with anxiety- that is, if they were present, chances are the autistic person would also feel anxious. These were Intolerance of Uncertainty, Sensory Differences, and Alexithymia. The first one I will cover below is Sensory Differences.

• Sensory Differences mean our brain interprets the information coming from our senses in a different way to others. This can our experience of the world can feel very "turned up" or "turned down", so things might seem very loud to us, for example. Or a food labelled "mild" could taste very strong to us.

So, we know sensory difficulties are quite a common part of the autistic experience, even if it isn't strictly needed for diagnosis on the DSM V. That being said you'd be hard pressed to find an autistic person who doesn't jump for joy at the thought of a quiet, darkened room with a soft blanket. There's a lot of research supporting that autistic children and adults have a different sensory profile*, ranging from fMRI studies that show more activation in a brain structure called our amygdala (linked to our anxiety response) in autistic people stimulated with noise (Green et al. 2013, 2015) to a study that found autistics reported being more sensitive to daily stimuli compared to a control (Corbett et al. 2016)

Why does this relate to anxiety? If there's more brain activity in our Anxiety Centre Amygdala when we have sensory input, that correlates with us feeling more anxious when we just hear a bit of noise compared to a neurotypical person. This was also found in mice interestingly enough- they were more anxious and socially interacted differently when their senses were messed with (trimming their whiskers at birth :( (Soumiya et al., 2016).

Also highlighted in this study was that autistics don't seem to "habituate" to stimuli as quickly as neurotypical controls- ie, while a neurotypical person will show less of a stress response after the fifth time of hearing the same noise, an autistic person won't- it'll be just as stressful to them. (Green et al. 2013, 2015). Not all research has supported this thought, check out the below graph that seems to show the group did habituate- but their startle response just didn't come down as much (Kohl et al, 2014).

Maybe we take longer to habituate, or is our base line arousal/startle just higher? (Kohl et al, 2014).

I reasonate, personally, with not habituating to things that cause me anxiety, at least not to the expected degree. As a therapist, I'm always teaching people about the mechanisms of our adaptive anxiety response, and the importance of repeating anxiety-provoking situations (in a gradual way) until we habituate to them. I always wondered why it never really seemed to work for me! Not to discount the evidence base of course, but I found it a little validating that my anxiety never quite seemed to reach the lower level.

The usual anxiety response- I wonder how this applies to autistic individuals? Definitely something for therapists to reflect upon.

Next I'll explore Intolerance of Uncertainty, what this means in research, and how it could explain part of our experience.

Green S. A., Rudie J. D., Colich N. L., Wood J. J., Shirinyan D., Hernandez L., et al. (2013). Overreactive brain responses to sensory stimuli in youth with autism spectrum disorders. J. Am. Acad. Child Adolesc. Psychiatry 52, 1158–1172. 10.1016

Green S. A., Hernandez L., Tottenham N., Krasileva K., Bookheimer S. Y., Dapretto M. (2015). Neurobiology of sensory overresponsivity in youth with autism spectrum disorders. JAMA Psychiatry 72, 778–786. 10.1001 Kohl, Sina & Wolters, Carolin & Gruendler, Theo & Vogeley, Kai & Klosterkötter, Joachim & Kuhn, Jens. (2014). Prepulse Inhibition of the Acoustic Startle Reflex in High Functioning Autism. PloS one. 9. e92372. 10.1371

Soumiya H., Godai A., Araiso H., Mori S., Furukawa S., Fukumitsu H. (2016). Neonatal whisker trimming impairs fear/anxiety-related emotional systems of the amygdala and social behaviors in adult mice.

South, M., & Rodgers, J. (2017). Sensory, Emotional and Cognitive Contributions to Anxiety in Autism Spectrum Disorders. Frontiers in Human Neuroscience, 11, 20. https://doi.org/10.3389/fnhum.2017.00020