Heterogeneity of autism symptoms in community-referred infants and toddlers at elevated or low familial likelihood of autism.

This research looked at young children (1-3 years old) who showed early autism signs. Children who had an older brother or sister with autism had milder autism symptoms, better thinking skills, and were less likely to have speaking delays compared to children with no family history of autism. This suggests that having autism in the family might influence how autism appears in younger children during their early development.

This study examined 121 community-referred infants and toddlers (12-36 months) with autism symptoms, comparing those with elevated familial likelihood (having an autistic sibling) to those with low familial likelihood (no family history). Children with autistic siblings demonstrated less severe autism symptoms, stronger cognitive abilities, and notably lower rates of expressive language delay compared to children without family history of autism. Receptive language delays occurred at similar rates across groups. After controlling for age and cognitive ability, children with autistic siblings remained significantly less likely to have expressive language delays.

These findings suggest familial likelihood influences the emerging autism phenotype in early development.

Family history should be considered when assessing autism presentations in young children. Children with autistic siblings may require different intervention approaches, particularly for expressive language development. Early identification strategies might need to account for phenotypic differences based on familial likelihood of autism.

Study design is unclear from the abstract. Participants were drawn from intervention trials which may limit generalizability. The study focuses on community-referred children, potentially excluding other populations. Sample sizes within subgroups were relatively small, particularly for the elevated likelihood group (n=30).

Evidence suggests autistic individuals at elevated familial likelihood of autism spectrum disorder (by virtue of having an autistic sibling) have stronger cognitive abilities on average than autistic individuals with no family history of the condition, who have a low familial likelihood of autism. Investigating phenotypic differences between community-referred infants and toddlers with autism symptoms at elevated or low familial likelihood of autism may provide important insight into heterogeneity in the emerging autism phenotype. This study compared behavioral, cognitive, and language abilities of community-referred infants and toddlers with confirmed autism symptoms at elevated (EL) or low familial likelihood of autism (LL). Participants were 121 children aged 12 to 36 months who participated in two larger randomized trials of parent-mediated interventions for children with autism symptoms.

Behavioral phenotypes were compared across three groups: children with at least one autistic sibling (EL-Sibs, n = 30), those with at least one older, non-autistic sibling and no family history of autism (LL-Sibs, n = 40), and first-born children with no family history of autism (LL-FB, n = 51). EL-Sibs had less severe autism symptoms and stronger cognitive abilities than children in LL groups. While the rate of receptive language delay was similar across groups, the rate of expressive language delay was markedly lower among EL-Sibs. After controlling for age and nonverbal cognitive ability, EL-Sibs were significantly less likely to present with expressive language delay than LL-Sibs.

Familial likelihood of autism may play an important role in shaping the emerging autism phenotype in infancy and toddlerhood.