Background
To examine the relationship between autism spectrum disorders (ASD) and specific language
impairment (SLI), family studies typically take a comparative approach where families
with one disease are examined for traits of the other disease. In contrast, the present
report is the first study with both disorders required to be present in each family
to provide a more direct test of the hypothesis of shared genetic etiology.
Methods
We behaviorally assessed 51 families including at least one person with ASD and at
least one person with SLI (without ASD). Pedigree members were tested with 22 standardized
measures of language and intelligence. Because these extended families include a nonshared
environmental contrast, we calculated heritability, not just familiality, for each
measure twice: 1) baseline heritability analysis, compared with; 2) heritability estimates
after statistically removing ASD subjects from pedigrees.
Results
Significant increases in heritability on four supra-linguistic measures (including
Pragmatic Judgment) and a composite language score but not on any other measures were
observed when removing ASD subjects from the analysis, indicating differential genetic
effects that are unique to ASD. Nongenetic explanations such as effects of ASD severity
or measurement error or low score variability in ASD subjects were systematically
ruled out, leaving the hypothesis of nonadditive genetics effects as the potential
source of the heritability change caused by ASD.
Conclusions
Although the data suggest genetic risk factors common to both SLI and ASD, there are
effects that seem unique to ASD, possibly caused by nonadditive gene-gene interactions
of shared risk loci.
Key Words
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Article info
Publication history
Published online: June 15, 2012
Accepted:
May 15,
2012
Received in revised form:
May 14,
2012
Received:
December 10,
2011
Identification
Copyright
© 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
