Phenotypic indicators predict ASD in siblings

Specific phenotypes of autism spectrum disorder, including issues with visual processing, found in older siblings are likely predictors of ASD in younger siblings, according to a study published in the American Journal of Psychiatry.

“While it is evident that brain development is atypical in infants who are later diagnosed with ASD, the link between brain maturation and inherited genetic factors is unclear,” Jessica B. Girault, PhD, an assistant professor in the department of psychiatry at the University of North Carolina at Chapel Hill, and colleagues wrote.

As previous research revealed that familial recurrence of ASD is predicted by a higher level of such traits in older siblings, researchers sought to examine associations between those traits and brain development in younger siblings.

The study involved 384 pairs of siblings, the oldest of which had been diagnosed with ASD. Girault and colleagues examined MRIs of their younger siblings’ brain development at 6, 12 and 24 months to assess total cerebral volume, cortical surface area, extra-axial cerebrospinal fluid, occipital cortical surface area and splenium white matter microstructure. Phenotyping for older siblings was done via tools such as the Social Communication Questionnaire (SCQ), the ADI-R and the Vineland Adaptive Behavior Scales. Higher scores on the former two indicate greater ASD symptoms and behaviors, while lower scores on VABS indicate lower adaptive functioning. Pearson correlations were created from older siblings’ SCQ score as well as the sibling phenotype for each of the three MRI time points.

Results showed that 89 younger siblings also exhibited ASD traits. In addition, higher levels of ASD traits for older siblings were associated with larger total cerebral volume and surface area as well as larger surface area and reduced white matter integrity in components of the visual system in younger siblings who developed ASD. This aligned with weaker functional connectivity between several networks and the visual system among all siblings during infancy.

“Targeting studies to the early postnatal period is likely to be critical, as growing evidence suggests that clinical symptomology after onset may be more driven by environmental and stochastic effects,” Girault and colleagues wrote.

Reference:

• Changes in brain’s visual area in infancy may precede autism diagnosis. https://www.nih.gov/news-events/news-releases/changes-brain-s-visual-areas-infancy-may-precede-autism-diagnosis. Published May 26, 2022. Accessed May 31, 2022.