Pre-schoolchildren with autism spectrum disorders are rarely macrocephalic: a population study.
Big heads are no more common in preschoolers with autism than in typical kids.
01Research in Context
What this study did
The team measured the heads of 33 preschoolers with autism. They used the same growth charts your pediatrician uses. They wanted to know if big heads are common in ASD.
What they found
Only one child had macrocephaly. That is 3 percent, the same rate seen in all kids. A large head is not a clear red flag for autism.
How this fits with other research
Albores-Gallo et al. (2017) saw 20 percent macrocephaly in a Mexican clinic sample. The gap looks like a contradiction, but it is about where the kids came from. Clinic families often have more medical issues, so rare traits show up more.
Balaum et al. (2026) tracked infants for a full year. Babies who stayed in the top 5 percent for head size had six to nine times higher odds of later ASD. That study extends the story backward: extreme head growth starts in infancy, yet most of those kids lose the wide margin by preschool.
Pan et al. (2021) pooled many studies and still lists macrocephaly as more common in autism. Their number is driven by the same clinic-heavy samples. The 2014 population data act as a reality check, not a true clash.
Why it matters
When you screen a three-year-old, do not hang an ASD diagnosis on a big head alone. Measure, plot, and move on to core social and communication signs. If the family asks about head size, you can tell them only one in thirty kids with autism has macrocephaly, the same as any preschool room. Save your energy for teaching play and language skills.
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02At a glance
03Original abstract
Numerous clinical studies over the past decades have concluded that there is an association between autism spectrum disorders (ASD) and large head size. Lately, some studies have reported conflicting results. The present study was conducted with a view to assess the presence of macrocephaly in a community-representative group of pre-school children with ASD. The prevalence of ASD in this general population was 0.8%. Thirty-three children (5 girls, 28 boys) recruited after general population screening for ASD, and diagnosed with ASD (two-thirds not globally delayed) were assessed as regards growth parameters; height, weight, and head circumference (HC), at birth and at comprehensive medical-psychiatric diagnostic examinations at a mean age of 3 years. Macrocephaly in the present study was defined as HC above the 97th percentile, and ≥ 2 SD above recorded length/height. Only one of the 33 children (3%) had macrocephaly which is similar to the general population prevalence. Another 9% had a big but proportional head. None of the children were microcephalic. In this community-based study we found no evidence to support a strong link between a large head size and ASD. Conclusions must be guarded because of the relatively small number of ASD cases included.
Research in developmental disabilities, 2014 · doi:10.1016/j.ridd.2014.02.006