Study reports associations between infants’ head growth patterns and risk of autism

A study of infants during their first year of life conducted in Israel found that children with consistently small or large head circumferences had around three times higher odds of being diagnosed with autism compared to infants whose head circumference was consistently medium. These odds were 6–10 times higher in the 5% of infants with the smallest head circumferences and the 5% of infants with the largest head circumferences. The research was published in Autism Research.

Autism, or autism spectrum disorder, is a neurodevelopmental condition characterized by differences in social communication, social interaction, and patterns of behavior, interests, or sensory processing. It is described as a spectrum because the type and intensity of characteristics vary widely between individuals.

Autism typically emerges in early childhood, although it may be formally diagnosed later in life. Researchers have investigated ways to detect autism in early childhood, and some studies suggested that abnormal head growth patterns in infancy may be associated with a subsequent diagnosis of autism.

Other studies have reported that children later diagnosed with autism spectrum disorder sometimes have very small heads at birth, followed by a period of accelerated growth of the head during infancy. There is some evidence that such an accelerated pace of head growth might begin before birth.

Study author Rewaa Balaum and her colleagues wanted to explore the relationship between head growth patterns during the first year of life and a later diagnosis of autism. They conducted a longitudinal study in which they looked into head circumference and height development trajectories.

Study participants included 262 children with autism and 560 non-autistic children born in the Negev, southern Israel, between 2014 and 2017. Their head circumference and height data during the first year of life were available in the databases of mother-child health clinics operated by the Israeli Ministry of Health.

Seventy-eight percent of participating children were boys, and 77% were Jewish. The ethnic groups living in the Negev are mainly Jews and Bedouin Arabs. Children with autism were less likely to come from families of high socioeconomic status compared to the control group. They also tended to have somewhat lower weight at birth (3.24 kg vs 3.32 kg) and somewhat lower head circumference (34.18 cm vs 34.88 cm).

Head circumference and height measurements of these infants were taken on multiple occasions during their first year of life. Using these data, study authors grouped participating infants into seven categories based on their head growth trajectories.

These trajectories were: infants with consistently small heads, infants with medium head circumference throughout infancy, infants with consistently large heads, infants whose head circumference increased from small to medium, those whose heads increased from medium to large, infants whose heads were large in the early days but decreased to medium by the end of the first year, and those whose heads were medium at birth but decreased to small near the end of the first year.

Results showed that infants with consistently large and consistently small heads were the most likely to be diagnosed with autism later. Their odds of being diagnosed with autism were around three times higher compared to infants with consistently medium-sized heads. These odds were 6–10 times higher in the 5% of infants with the smallest heads and the 5% of infants with the largest head circumferences.

Crucially, the researchers found that these head growth patterns were strongly linked to height. Children with atypical head sizes also tended to have atypical heights. The highest risk for autism was observed in children who had both atypical head size and atypical height, rather than those with isolated head growth issues.

“Our findings suggest that the reported associations between atypical head growth during infancy and ASD [autism spectrum disorder] may be attributed to broader physical growth anomalies. This conclusion highlights the importance of a multifaceted, longitudinal examination of such anthropometric measures in studies of child development,” the study authors concluded.

The study contributes to the scientific understanding of autism. However, it should be noted that the study only looked at children in the first year of life. It remains unknown whether these growth patterns continue beyond this period. It also remains unknown how much these findings can be generalized to human populations outside southern Israel.

The paper, “Head Growth Trajectories During the First Year of Life and Risk of Autism Spectrum Disorder,” was authored by Rewaa Balaum, Leena Elbedour, Einav Alhozyel, Gal Meiri, Dikla Zigdon, Analya Michaelovski, Orly Kerub, and Idan Menashe.