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Understanding comorbidity: A twin study of reading disability and attention‐deficit/hyperactivity disorder
Author(s) -
Willcutt Erik G.,
Pennington Bruce F.,
Olson Richard K.,
DeFries John C.
Publication year - 2007
Publication title -
american journal of medical genetics part b: neuropsychiatric genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.393
H-Index - 126
eISSN - 1552-485X
pISSN - 1552-4841
DOI - 10.1002/ajmg.b.30310
Subject(s) - comorbidity , attention deficit hyperactivity disorder , reading disability , twin study , psychology , impulsivity , heritability , proband , clinical psychology , bivariate analysis , psychiatry , developmental psychology , reading (process) , dyslexia , genetics , biology , political science , gene , law , mutation , statistics , mathematics
A community sample of twins in which at least one member of each pair exhibited significant reading difficulties (99 monozygotic and 80 dizygotic pairs) or symptoms of attention‐deficit/hyperactivity disorder (ADHD; 83 monozygotic and 78 dizygotic pairs) was used to test the etiology of comorbidity between reading disability (RD) and ADHD. Univariate analyses revealed moderate to high heritability for all measures of reading difficulty and ADHD. Subsequent bivariate analyses indicated that the relation between reading difficulties and inattention symptoms is primarily attributable to common genetic influences, whereas bivariate heritability estimates were not significant for hyperactivity‐impulsivity and any of the reading measures. Reading difficulties and ADHD symptoms were more highly heritable if the proband met criteria for both disorders versus RD or ADHD alone, suggesting that future molecular genetic analyses of comorbid RD + ADHD may facilitate the identification of susceptibility genes for RD, ADHD, and their comorbidity. © 2007 Wiley‐Liss, Inc.