Serotonergic innervation of the amygdala is increased in autism spectrum disorder and decreased in Williams syndrome.
C H Lew, K M Groeniger, K L Hanson and 6 others
PMID 32024554WHAT IT FOUND
Postmortem brain tissue showed denser serotonin fibers in the amygdala of people with autism than with Williams syndrome.
Neither group differed significantly from neurotypical controls. This describes brain structure, not how to treat patients.
Key findings
01Serotonin fiber density was significantly higher in autism than in Williams syndrome across three amygdala nuclei.
02There were no significant differences in serotonin fiber density between neurotypical controls and either autism or Williams syndrome.
03The study examined postmortem tissue from 20 subjects, including a single infant pair, limiting generalisability.
STILL TO COME
How it was doneWhat they found
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What it does not show
The sample size is very small (20 subjects total), which limits the ability to detect differences against controls. The study used postmortem tissue, so it cannot link brain structure to live behavioral responses or treatment outcomes. Diagnostic groups were not matched for sex or hemisphere due to tissue availability. There was no infant comparison group for autism, so developmental changes could not be assessed in that disorder.
The easy way to misread this
Do not assume that serotonin fiber density is definitively abnormal in autism or Williams syndrome compared to typical development. The study found no significant difference between either disorder and neurotypical controls; the only significant finding was the difference between the two disorders themselves.