1) To identify a subset of children with autism spectrum disorder (ASD) and co-occurring symptoms of psychopathology. 2) To evaluate associations between this subgroup and biological sex and amygdala volume.
Participants included 420 children (ASD: 91 girls, 209 boys; typically developing controls: 57 girls, 63 boys). Latent profile analysis was used to identify ASD subgroups based on symptoms of psychopathology, adaptive functioning, cognitive development, and autism severity. Sex differences in the proportion of girls and boys in each subgroup were evaluated. MRI scans were acquired (346 children); amygdala volumes were evaluated in relation to subgroups and problem behavior scores.
Three ASD subgroups were identified; one was characterized by high levels of psychopathology and moderate impairment on other measures (High Psychopathology Moderate Impairments [HPMI], comprising 27% of the sample). The other two subgroups had lower symptoms of psychopathology but were differentiated by high and low levels of impairment on other measures. A higher proportion of girls were classified into the HPMI subgroup (40% of girls vs. 22% of boys). Relative to controls, amygdala volumes were enlarged only in the HPMI subgroup, other subgroups did not differ. There was a positive association between right amygdala volume and internalizing behaviors in girls but not boys with ASD.
A higher proportion of girls with ASD faced greater challenges with psychopathology, suggesting a need for closer evaluation and potentially earlier intervention to help improve outcomes. Amygdala enlargement was associated with co-occurring symptoms of psychopathology and sex-specific correlations with symptoms were observed.

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