Characteristics of the broader phenotype in autism: A study of siblings using the Children's Communication Checklist-2
Department of Experimental Psychology, Oxford University, Oxford, United Kingdom.American Journal of Medical Genetics Part B Neuropsychiatric Genetics (Impact Factor: 3.42). 03/2006; 141B(2):117-22. DOI: 10.1002/ajmg.b.30267
Non-autistic relatives of people with autistic disorder have an increased risk of social and communicative difficulties: this is known as the "broad phenotype." Better methods for characterizing the broad phenotype are needed to facilitate identification of risk genes for autism. 29 siblings of 20 children with autistic disorder, 13 siblings of 9 children with PDDNOS, and 46 typically developing control children from 26 families were assessed by parental report using the Children's Communication Checklist-2 (CCC-2). Groups were matched on age and IQ and siblings with autism were excluded. Group mean scores on the CCC-2 differed on only one subscale, syntax. However, siblings of children with autism or PDDNOS were over-represented in the tails of the distributions of several scales, and 10 (24%) scored more than 2 SD below the control mean on a total score based on all 10 subscales. Only two of these 10 children scored above threshold on one or more scales of the Autism Diagnostic Interview-Revised (ADI-R). Children with abnormal scores on the CCC-2 total were characterized by low-verbal IQ and their fathers tended to score high on the social and communication scales of the Autism Quotient, a measure of the broad phenotype in adults. The CCC-2 shows promise as a quick screening device for the broad phenotype in non-autistic siblings of children with autism.
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- "We hypothesized that our school-aged sample would display unimpaired receptive/expressive language but would display deficits relative to norms on one or more of the remaining domains. In pragmatics, we extended the work of Bishop et al. (2006) and Ben-Yizhak et al. (2011) by including a standardized direct assessment measure and comparing results with a parent questionnaire. Given the evidence of BAP in siblings of children with ASD as well as Ben-Yizhak's et al. (2011) preliminary results of impairments in pragmatic language, we hypothesized that non-ASD siblings would be impaired on measures of pragmatic language. "
ABSTRACT: Siblings of children with autism spectrum disorder (ASD) who do not have ASD outcomes are more likely than their peers to experience delays in language acquisition as preschoolers. However, less is known about how these siblings are faring when they are school-aged. We examined language-related abilities of 18 siblings with non-ASD outcomes, aged 8–11. On average, siblings performed more poorly than the normative sample in phonological memory and phonological awareness. In contrast, word-level reading was unimpaired. No deficits relative to norms were found on a direct child assessment and parent-report measure of pragmatic language; however, recommendations for further research in this area are made. Comparing two direct child assessments, this sample performed more poorly in pragmatics than receptive/expressive language. Language abilities in siblings of children with ASD is an area ripe for further investigation with larger sample sizes and appropriate comparison groups.
- "Difficulties include, among others: pragmatic language deficits (e.g.        ), verbal fluency , reading abilities  , delay of language development and problems in language developmental history    , conversational skills  and syntax . "
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- "Rather than treating ASD as discrete entities with a categorical approach based on a distinct boundary between normality and pathology, several authors   have suggested a dimensional approach to ASD, which conceptualises these disorders as the upper extreme of a constellation of deficits in social adaptation and communication that may be continuously distributed in the population . There are several lines of evidence for this notion: autistic traits measured in the general population show a smooth distribution throughout the normal range to the clinical extreme  ; relatives of patients with ASD display high levels of autistic traits  ; factor analytic approaches did not detect discontinuities between ASD and autistic traits ; known risk factors for ASD (e.g., paternal age at birth) have been shown to influence autistic traits ; common genetic variants that are, by their very nature, present in a significant proportion of the general population, are believed to play a role in the aetiology of ASD   . Indeed, the DSM-5 itself has highlighted the dimensional nature of the cardinal behavioural domains of ASD, by incorporating a severity scale to capture the 'spectrum' nature of ASD . "
ABSTRACT: Background: In recent years, several twin studies adopted a dimensional approach to Autism Spectrum Disorders (ASD) and estimated the contribution of genetic and environmental influences to variation in autistic traits. However, no study was performed on adults over 18 years of age and all but two studies were based on parent or teacher ratings. Also, the genetic and environmental contributions to the interplay between autistic traits and adult personality dimensions have not been investigated. Methods: A sample of 266 complete twin pairs (30% males, mean age 40 ± 12 years) drawn from the population-based Italian Twin Register was administered the Autism-Spectrum Quotient, Temperament and Character Inventory (TCI-125), and General Health Questionnaire (GHQ-12). Genetic structural equation modelling was performed with the Mx program. Estimates were adjusted for gender, age, and GHQ-12 score. Results: Genetic factors accounted for 44% and 20%-49% of individual differences in autistic traits and TCI dimensions, respectively. Unshared environmental factors explained the remaining proportion of variance. Consistently with the notion of a personality profile in ASD characterised by obsessive temperament, autistic traits showed significant phenotypic correlations with several TCI dimensions (positive: HA; negative: NS, RD, SD, C). Genetic and unshared environmental correlations between AQ and these TCI dimensions were significant. The degree of genetic overlap was generally greater than the degree of environmental overlap. Conclusions: Despite some limitations, this study suggests that genetic factors contribute substantially to individual differences in autistic traits in adults, with unshared environmental influences also playing an important role. It also suggests that autistic traits and the majority of temperament and character dimensions share common genetic and environmental aetiological factors.
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