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Comparing Eye-tracking Data of Children with High-functioning ASD, Comorbid ADHD, and of a Control Watching Social Videos
Published on: December 7, 2018
Rethinking shared environment as a source of variance underlying attention-deficit/hyperactivity disorder symptoms:
Alexis C Wood1, Jan Buitelaar, Fruhling Rijsdijk
1Department of Epidemiology and Section on Statistical Genetics, University of Alabama at Birmingham, AL 35294, USA. LekkiWood@Gmail.com
Abstract:
Burt (2009) recently published a meta-analysis of twin studies on behaviors associated with childhood psychopathologies, concluding that the finding that traits associated with attention-deficit/hyperactivity disorder (ADHD) were the only behaviors that did not show a significant influence of shared environment (C) was surprising. We agree, highlighting four methodological issues that may account for this finding: (a) the use of nonlinear transformations to normalize skewed data; (b) low power to detect C and the subsequent presentation of reduced models; (c) the negative confounding of dominant genetic (D) and C influences in twin models with data exclusively from monozygotic and dizygotic twin pairs reared together; and (d) the correction used for contrast effects (a form of rater bias), which may lead to an overestimate of additive genetic (A) or D parameters at the expense of C. We offer suggestions for future research to address these issues, and we emphasize the need for additional research to examine possible shared environmental factors related to ADHD.
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