ISRAEL, An Israeli study published in Cerebral Cortex found virtually no anatomical differences between the brains of subjects with autism and those of subjects without the diagnosis. Researchers compared structural MRI scans from 539 individuals diagnosed with high-functioning autism to 537 subjects from a control group. The data was provided by the public Autism Brain Imaging Data Exchange (ABIDE) database.
The research team found no difference in intracranial volume (brain size) between the two groups. The ASD group showed a small increase in ventricle volume, a difference that also shows up in the brains of individuals diagnosed with schizophrenia, dementia, and other brain disorders.
The research team was particularly interested in looking at the thickness of the brain’s cortex, as previous studies have suggested the individuals with cortical thickness (the thickness of the brain’s folds) tended to have greater impairments in social interactions and relationships. A technique called linear discriminant analysis allowed team members to explore the differences from several angles. They found that differences occurred only 50 to 60% of the time.
Researcher Shlomi Haar and colleagues concluded,
“These results suggest that many of the previously reported anatomical abnormalities are likely to be of low scientific and clinical significance, . . . anatomical differences between high-functioning ASD and control groups (aged 6-35 years old) are very small in comparison to large within-group variability. This suggests that anatomical measures alone are likely to be of low scientific and clinical significance for identifying children, adolescents and adults with ASD or for elucidating their neuropathology.”
Based on this study, it seems likely that autism does not affect the brain’s physical anatomy, but is instead caused by functional differences, in spite of previous studies with smaller sample groups that found statistically significant differences.