Focused on the genetic liability for the broad phenotype of autism as well as the possible influence of having a sibling with autism.

We compared the cognitive and language development at 4, 14, 24, 36, 54 months, and 7 years of siblings of children with autism (SIBS-A) to that of siblings of children with typical development (SIBS-TD) using growth curve analyses. At 7 years, 40% of the SIBS-A, compared to 16% of SIBS-TD, were identified with cognitive, language and/or academic difficulties, identified using direct tests and/or parental reports. This sub-group was identified as SIBS-A-broad phenotype (BP). Results indicated that early language scores (14-54 months), but not cognitive scores of SIBS-A-BP and SIBS-A-nonBP were significantly lower compared to the language scores of SIBS-TD, and that the rate of development was also significantly different, thus pinpointing language as a major area of difficulty for SIBS-A during the preschool years.

Cognitive and language skills of 39 siblings of children with autism (SIBS-A) and 39 siblings of typically developing children (SIBS-TD) at ages 4, 14, 24, 36, and 54 months were compared. Twelve of the 39 SIBS-A revealed a delay in cognition and/or language (including one child diagnosed with autism) compared to only two SIBS-TD. Developmental trajectories revealed that the cognitive differences disappeared by age 54 months, but some differences in language ability remained. Thus, most SIBS-A were well-functioning, but some revealed cognitive and/or language difficulties during the preschool years. Even these siblings by and large caught up by the age of 54 months, with receptive and expressive language abilities remaining an area of difficulty for some earlier identified siblings.

The cognitive and language skills of 30 siblings of children with autism (SIBS-A) and 30 siblings of typically developing children (SIBS-TD) were compared. Non-significant group differences emerged for cognition at both ages. At 24 months, significantly more SIBS-A demonstrated language scores one or two standard deviations below the mean compared to SIBS-TD. At 36 months, the groups differed significantly in receptive language, and more SIBS-A displayed receptive and expressive difficulties compared to SIBS-TD. Six SIBS-A (including one diagnosed with autism) revealed language scores more than two standard deviations below the mean at both ages, a pattern not seen in the SIBS-TD. Results are discussed in reference to language difficulties in autism spectrum disorders and the genetic liability for autism.

Deficits in theory of mind (ToM), evident in most individuals with autism, have been suggested as a core deficit of autism. ToM difficulties in young siblings of children with autism (SIBS-A) compared to siblings of typically developing children (SIBS-TD) would place the former within the broad phenotype. We examined ToM's possible associations with measures of language, cognition, and daily living skills. Participants comprised 24 SIBS-A and 24 matched SIBSTD aged 4.6 years. They completed the false belief and the strange stories tasks. We also collected measures of verbal and cognitive ability and daily living skills. Non-significant differences emerged between the groups on both ToM tasks. Differences did emerge in within-group associations between ToM ability and receptive language. The conclusion is that SIBS-A show resilience in ToM abilities. Possibly, these deficits are not genetically transferred to siblings, at least as measured in laboratory-based ToM tasks.