The amygdala, anxiety and Autism Spectrum Disorder
Regions of the amygdala, highlighted by different colours.
Source: https://doi.org/10.1002/hbm.26005
In an effort to better understand why anxiety is prevalent in people with neurodevelopmental disorders, researchers at Western University have been studying the brain to search for answers. A recent study from the group found that one region of the brain, the amygdala, is enlarged in children with Autism Spectrum Disorder (ASD) who also have anxiety.
The amygdala is a small part of the brain that is commonly associated with the control of emotions and emotion-related behaviour. In particular, the amygdala plays an important role when we experience fear or are faced with something threatening. For example, you may be overwhelmed with a fleeting feeling of fear when a spider appears out of nowhere, or you may have extreme nervousness in the run up to an important presentation. During these times, the amygdala is working hard behind the scenes, processing the incoming information and sending out commands to other brain areas.
This small, almond-shaped brain region is made up of many smaller parts, known as the subnuclei (highlighted by the different colours in the image). It is located in a very central part of the brain and is well connected to other important regions, acting as a hub for information coming into the brain before it is passed onto other brain regions. Because of its many connections and role in emotion processing, the amygdala has been identified as an area highly linked with anxiety disorders. Experience of anxiety over long periods of time often has similar effects on the brain as chronic stress. This can alter brain structure and has even been linked to the onset of neuropsychiatric disorders as discussed here.
Anxiety can be found at a higher rate in children with neurodevelopmental disorders, which can include autism spectrum disorder and attention deficit hyperactivity disorder (ADHD), compared to their typically developing peers. It has been reported that over 85% of children with ASD* show some symptoms of anxiety in their daily life, with almost 40% of these children having a diagnosed anxiety disorder (see the study here). The prevalence of anxiety in children with ADHD is similarly high. This is a concerning statistic, as anxiety can significantly reduce the quality of life of an individual and is thought to be a risk factor for adverse mental health outcomes. The societal problems associated with anxiety have raised questions about how and when we might be able to detect anxiety in the brain.
In a recent study, led by Dr. Emma Duerden at Western University, researchers sought to better understand how the amygdala is associated with anxiety. The work looked at typically developing children and children with neurodevelopmental disorders (including ASD and ADHD), assessing whether the size of the amygdala subnuclei may provide any insight. In total, data from 233 participants were analysed, with ages ranging from 6-18 years. This included children who were clinically diagnosed with ASD, children with ADHD, and some typically developing children. Anxiety was measured using a commonly used questionnaire completed by the parents. To determine the volume of the different subnuclei volumes, children underwent a brain scan to take a detailed image of the brain. The amygdala was later identified in the images and divided into subnuclei using an advanced algorithm.
Following analysis, it was found that certain parts of the amygdala were enlarged in children with autism who also had anxiety. This finding did not extend to the typically developing children, autistic children without anxiety, or those with ADHD. At this point, it remains difficult to determine the role of the different amygdala components in anxiety. However, this work highlights one part of the amygdala, the central amygdala, as a potential key to understanding the mechanisms of anxiety in the brain more clearly. While the differences between the groups are relatively small, researchers hope this line of work will continue on a larger scale, by looking at more people or by following groups to study changes over time. The authors of the study highlight that, from this work, it is not possible to disentangle the direction of the effect. In other words, it is unclear whether the enlarged part of the amygdala is a result of increased and prolonged anxious experience, or if having larger amygdala subnuclei increases the chance of having anxiety in the first place.
It is important to understand how the amygdala develops and identify how changes in this small structure may relate to mental health and disorders of the brain. A better understanding of these brain regions will help to provide answers about how behavioural pathologies, like anxiety, are manifested in the brain. As research in this field continues to become more sophisticated, it is possible that work will eventually be able to uncover new diagnostic markers for brain health, with the end goal of more advanced, targeted treatments for anxiety. This is of particular importance, because current treatments and therapies for anxiety are reportedly less effective for people with autism than those without autism.
* Please note: the author has chosen to use terminology that reflects what is used in the original research paper (person-first language), but acknowledges that there are many who prefer identity-first language (e.g., “autistic person”).
Original article: Seguin, D., Pac, S., Wang, J., Nicolson, R., Martinez-Trujillo, J., Anagnostou, E., Lerch, J. P., Hammill, C., Schachar, R., Crosbie, J., Kelley, E., Ayub, M., Brian, J., Liu, X., Arnold, P. D., Georgiades, S., & Duerden, E. G. (2022). Amygdala subnuclei volumes and anxiety behaviors in children and adolescents with autism spectrum disorder, attention deficit hyperactivity disorder, and obsessive–compulsive disorder. Human Brain Mapping, 1– 12. https://doi.org/10.1002/hbm.26005
Other references:
https://www.sciencedaily.com/releases/2016/01/160121121818.htm
https://www.spectrumnews.org/news/anxiety-drives-amygdala-differences-in-autistic-youth/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5487760/