SLPCohortJournal of autism and developmental disorders2026

A Longitudinal Study of Head Circumference Trajectories in Autism and Autistic Traits.

Sarah A Ashley, Kate Merritt, Francesca Solmi and 3 others

PMID 39395125

WHAT IT FOUND

Children with autism had larger head circumference than controls, but the difference disappeared when height was considered.

Children with elevated autistic traits showed no initial difference and only a small lower head circumference after accounting for sex.

Key findings

01Children with an ASD diagnosis had larger head circumference trajectories than controls after accounting for sex and background factors, but the difference was no longer present when height was included.

02Children with elevated autistic traits had no head circumference difference before accounting for sex, then a lower head circumference after accounting for sex, which weakened when height was included.

03The largest head circumference difference in the ASD group was seen in the small subgroup with cognitive learning needs, but the subgroup was too small to rely on.

STILL TO COME

How it was doneWhat they foundWhat it means for SLPs

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What it does not show

Only 78 children with an ASD diagnosis were analysed, so the autism findings depend on a small group. ASD status came from parent report at age 9, not a formal diagnostic assessment. The sample was 94% white, so the findings may not apply to other ethnic groups. Many children lacked complete data, and the analysed sample differed slightly from the full cohort in gestational age and birth weight. Head circumference was measured at uneven times, and only timepoints with at least 10 participants per group were used. Adjusting for height removed the ASD head circumference difference, so the study cannot separate head growth from general body growth. The ASD subgroup with cognitive learning needs contained only 13 children, so that subgroup finding is fragile. Females were underrepresented in the ASD group, so sex differences could not be reliably tested.

Declared interests

The only funding information given names the Beatrice and Samuel A. Seaver Foundation and the Medical Research Council.

The easy way to misread this

Do not use head circumference to diagnose autism or choose therapy. The ASD difference disappeared after height was considered, and the autistic trait difference was not seen without accounting for sex.

Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →