While it is widely established that individuals with ASD have varied cognitive profiles (Goldstein et al., 2008; Szatmari et al., 1995; Zander & Dahlgren, 2010; Ventola et al., 2010), little is known about the cognitive profiles of their unaffected siblings. The few studies that have been conducted have yielded mixed results. While overall cognitive abilities are generally found to be comparable between individuals who do and do not have a sibling with ASD, some studies have reported language or verbal weaknesses in individuals with siblings with ASD (Yirmiya et al., 2007; Gamliel et al., 2009). In addition, some studies (Fombonne et al., 1997; Folstein et al., 1999) have found a higher degree of variability in the cognitive profiles of siblings of individuals with ASD.
Objectives:
To further elucidate the nature of cognitive profiles of siblings of children with ASD.
Methods:
The DAS-II School Age Battery was administered to 50 siblings of children with autism spectrum disorders who participated in an MRI study at the Yale Child Study Center. The sample ranged in age from 5 to 16 years (mean = 11.3, s.d. 2.9) with a mean GCA score of 110.4 (s.d. 17.2).
Results:
Intra-individual discrepancies greater than 1 s.d. (15 points) in either direction were found at the following frequencies: verbal (V) vs. nonverbal (NV) abilities (38%); V vs. spatial (S) abilities (34%); NV vs. S abilities (20%). These frequencies are higher than would be expected based on the normative sample. Discrepancies of greater than 2 standard deviations were less frequent, but still greater than what would be expected based on the normative sample. However, this was entirely attributable to brothers, who exhibited discrepancies at notably higher rates than the normative sample (V vs. NV: 11.1%, V vs. S: 11.1%, NV vs. S: 3.7%). None of the sisters in the sample showed discrepancies between any domains that exceeded 2 standard deviations. No clear pattern emerged with regard to the direction of the discrepancies. There were no significant differences between domain standard scores for the sample as a whole (reflecting the lack of directionality of the discrepancies), and standard deviations for each domain were comparable to the general population, suggesting typical levels of inter-individual variability for each domain.
Conclusions:
Siblings with autism spectrum disorders were found to have more intra-individual variability in their cognitive profiles than the general population. Despite prior findings of verbal weaknesses in siblings, the present study found no clear directionality to the cognitive discrepancies, with some individuals showing verbal strengths and others showing verbal weaknesses. Frequencies of discrepancies among cognitive domains in siblings were generally similar to those previously found in children diagnosed with an autism spectrum disorder (Ventola, 2010). These results are consistent with Kaiser et al.’s (2010) finding of shared dysfunction between children with ASD and their unaffected siblings, and provide further support for a common genetic vulnerability.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype