A unique neural and behavioral profile of social anxiety in autism.

Social anxiety (SA) commonly co-occurs with autism spectrum disorder (ASD), each sometimes misdiagnosed as the other. We examine behavioral and neural profile of SA in ASD in an online study (ASD = 575, control = 357) and a neuroimaging study (ASD = 72, control = 72). Using a naturalistic social interaction task, we identified acquiescent behaviors in individuals with both SA and ASD compared to those with ASD or SA alone. The amygdala-previously linked to anxiety and ASD-was uniquely enlarged only in adults with both SA and ASD. Furthermore, larger amygdala volume was associated with acquiescent behaviors in ASD, a relationship that was enhanced when accounting for SA. These findings suggest that autistic adults with larger amygdala are more likely to experience SA and difficulties in power dynamics (dominance or control), highlighting unique phenotype of SA in ASD.