Anxiety is on the rise in children overall, including children with autism. The estimated rate of anxiety in autism is as high as 40%. There are reports of dynamic changes in brain function among children diagnosed with autism, particularly between two to six years of age. The complexity and timing of these changes have left a number of open questions and inconsistent findings in unrelated studies.
Studies of emotional differences have led to interest in the amygdala, a part of the brain involved in emotional processing. Past studies have focused on amygdala volume differences between children with autism and typically developing peers, but these studies have also led to mixed conclusions. A research team at the Children’s Hospital of Philadelphia looked at three categories of patients including sixty-three patients with both autism and anxiety, twenty-four patients with autism without anxiety, and the third group of twenty-nine typically developing children with neither autism nor anxiety (control group). The authors predicted that there would be a change in the overall size (volume) of the amygdala in the autism+anxiety group compared to the other two groups, which could account for the variation in the results in earlier studies.
The results identified significant volume reductions in the right amygdala among the autism+anxiety cohort in comparison with the autism without anxiety and typically developing control group. The volume changes specifically impacted the area called the lateral nucleus with dorsal extensions into the basolateral and central nuclei. The authors explained the results as likely related to a process called neuroexcitotoxicity, in which specialized cells that work to prune brain cell connections become hyperactivated. These cells, called microglia, become activated and clear debris due to brain injuries from trauma and stroke. The study also found an increase in total brain volume in patients with autism and anxiety, which has been previously reported in regressive autism. This is the first study to examine the features of the brain in autism with anxiety.
Future studies could investigate why only the right amygdala demonstrates these specific volume changes among this particular autism phenotype. It would be important to study the environmental and genetic factors that lead to developmental neuroexcitotoxicity, and determine which biological pathway(s) lead to amygdala volume reductions. The study received ethical approval and participated in complete informed consent among the Children’s Hospital of Philadelphia Institutional Review Board. Authors Herrington, Miller, and Schultz reported a conflict of interest in research funds received by pharmaceutical companies. The remaining coauthors did not declare any potential conflicts of interest.
The study points to increased amygdala volume in a subset of the autism population while defining a unique autism phenotype.
More Info: Herrington, J., Maddox, B., Kerns, C., Rump, K., Worley, J., . . . Miller, J. (2017). DOI: 10.1007/s10803-017-3206-1
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