LAUSR

The neurobiology of autism has been shown to involve alterations in cortical morphology and gamma‐aminobutyric acid A (GABAA) receptor density. We hypothesized that GABAA receptor binding potential (GABAAR BPND) would correlate with cortical thickness, but their correlations would differ between autistic adults and typically developing (TD) controls. We studied 50 adults (23 autism, 27 TD, mean age of 27 years) using magnetic resonance imaging to measure cortical thickness, and [18F]flumazenil positron emission tomography imaging to measure GABAAR BPND. We determined the correlations between cortical thickness and GABAAR BPND by cortical lobe, region‐of‐interest, and diagnosis of autism spectrum disorder (ASD). We also explored potential sex differences in the relationship between cortical thickness and autism characteristics, as measured by autism spectrum quotient (AQ) scores. Comparing autism and TD groups, no significant differences were found in cortical thickness or GABAAR BPND. In both autism and TD groups, a negative relationship between cortical thickness and GABAAR BPND was observed in the frontal and occipital cortices, but no relationship was found in the temporal or limbic cortices. A positive correlation was seen in the parietal cortex that was only significant for the autism group. Interestingly, in an exploratory analysis, we found sex differences in the relationships between cortical thickness and GABAAR BPND, and cortical thickness and AQ scores in the left postcentral gyrus.