High-Atypicality Autism Siblings: a Prospective Study of Mother-Infant Interactions

Background: Infant siblings of children with autism spectrum disorder (A-sibs) –who are themselves at genetic risk of autism –are more likely to exhibit early social and communicative impairments than typically developing siblings (TD-sibs). Recent prospective observational studies, including our own, further found that mother-infant interactions in A-sibs show specific subtle but consistent impairments in early-middle infancy, which may exacerbate the infants’ social atypicalities through their experiencing or seeking of a less optimal early interactive environment. Little is known about the developmental trajectory of such mother-infant interactions through the first year.

Objectives: To compare mother-infant interaction characteristics: (1) between A-sib infants with and without high phenotypic autism risk, and TD-sib controls in a follow-up at 12-15 months; (2) within groups to investigate longitudinal consistency between 6-10 months and 12-15 months.

Methods: Fifty-five mother-infant unstructured play interactions were rated, blind to dyad information, using a global rating scale on which we have previously reported validation and reliability data, and adapted for a slightly older age group. Infants were 12- to 15-month-old A-sibs at high phenotypic risk (i.e. top quartile scores on an independent standardised measure of autism phenotype behaviour) and low phenotypic risk, and TD-sib controls.

Results: We previously reported that A-sib infants with high phenotypic atypicality at 6-10 months were more likely to exhibit mildly avoidant interactive behaviour, and – as a group – their mothers were significantly less sensitive and less accepting of their infant’s behaviour. Here, we attempt to replicate in the same sample these findings at 12-15 months, and will report whether such interactive impairments could be predicted by interactions or phenotypic atypicality at 6-10 months. We will also present findings at both time points after controlling for infant temperament and IQ.

Conclusions: This study was the first to show prospectively that A-sib infants at high phenotypic risk and their mothers tend to exhibit interactive impairments at 6-10 months. The stability or exacerbation of such impairments in middle infancy would have clear implications for prodromal intervention.