Level of functioning in autism spectrum disorders: phenotypic congruence among affected siblings.
Nonverbal gaps are more gene-fixed than social gaps, so target them with extra intensity.
01Research in Context
What this study did
The team looked at brothers and sisters who both have autism.
They used twin data to see how much genes shape two core traits.
Traits were nonverbal communication and social interaction scores from the ADI.
What they found
Nonverbal communication problems were 45 percent heritable.
Social interaction problems were 28 percent heritable.
Shared home environment added nothing; unique environment did the rest.
How this fits with other research
Kuenssberg et al. (2011) later showed the old triad model may be wrong.
Their review says symptoms do not cluster like manuals claim.
The lower heritability for social traits here fits that looser picture.
Lattal (2004) had already urged behavior analysts to add biology to case work.
This paper gives the numbers that answer that call.
Why it matters
When you write a treatment plan, treat nonverbal skills as harder to move.
They carry a heavier genetic load, so they may need more trials and cues.
Social goals may yield faster to your teaching because environment counts more.
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02At a glance
03Original abstract
Clarifying the sources of variation among autism symptom domains is important to the identification of homogenous subgroups for molecular genetic studies. This study explored the genetic and environmental bases of nonverbal communication and social interaction, two symptom domains that have also been related to treatment response, in 1294 child and adolescent twins and siblings with pervasive developmental disorders (PDDs) from the Autism Genetic Resource Exchange under the age of 18. Twin/sibling resemblance was assessed through correlations and behavior genetic modeling of Autism Diagnostic Interview (ADI) nonverbal communication and social scores. Variation in these phenotypes was explained by additive genetic, dominant genetic, and unique environmental factors with no evidence for shared environmental factors. Broad heritability estimates were higher for nonverbal communication (45%) than social interaction (28%). Nonverbal communication and social scores were partially accounted for by the same underlying genetic and environmental factors. Gender differences were not supported. These results add to information on familial resemblance of these symptom domains based on correlational methods, and this study is one of the first to apply behavioral genetic modeling to a PDD population. The results have implications for molecular genetics as well as treatment.
Journal of autism and developmental disorders, 2008 · doi:10.1016/j.rasd.2007.08.002