Larger brains in medication naive high-functioning subjects with pervasive developmental disorder.

Researchers scanned the brains of high-functioning teens and adults with pervasive developmental disorder. All were medication-free. They compared gray-matter volume, cerebellum size, and ventricle width to matched controls using MRI.

The team wanted to know if brain enlargement seen in younger kids with autism persists into later life.

The ASD group showed larger gray-matter volume across the whole brain. Their cerebellums were also bigger, and their brain ventricles were disproportionately enlarged.

These changes were present even though the participants had never taken psychiatric drugs.

Bai et al. (2023) extends this finding downward: toddlers as young as 2 already show extra gray-matter volume. Seng et al. (2022) narrows the focus, linking specific cerebellum and left supramarginal gyrus size to insistence-on-sameness traits in high-schoolers.

Storch et al. (2012) seems to contradict the result: 90% of routine clinical MRI reports on high-functioning kids were read as "normal." The difference is method: C et al. used precise volume math, while A et al. relied on standard radiology reports that can miss subtle enlargement.

Mahajan et al. (2016) adds that overgrowth also shows up in sensorimotor cortex, and the pattern changes when ADHD is present.

If you assess teens or adults with ASD, remember that "normal" clinical MRI reports do not rule out measurable brain-volume differences. When you see persistent rigidity or motor quirks, consider that underlying cerebellar or sensorimotor enlargement may be part of the picture. This reminds us to pair behavioral data with sensitive imaging when medical teams request it, and to avoid assuming brain development has "caught up" just because the person is older.