Exploring how symptoms of attention-deficit/hyperactivity disorder are related to reading and mathematics performance: general genes, general environments

Abstract

Children with attention-deficit/hyperactivity disorder (ADHD) tend to perform more poorly on tests of reading and mathematical performance than their typical peers. Quantitative genetic analyses allow for a better understanding of the etiology of ADHD and reading and mathematics outcomes, by examining their common and unique genetic and environmental influences. Analyses were conducted on a sample 271 pairs of 10-year-old monozygotic and dizygotic twins drawn from the Western Reserve Reading and Mathematics Project. In general, the results suggested that the associations among ADHD symptoms, reading outcomes, and math outcomes were influenced by both general genetic and general shared-environment factors. The analyses also suggested significant independent genetic effects for ADHD symptoms. The results imply that differing etiological factors underlie the relationships among ADHD and reading and mathematics performance. It appears that both genetic and common family or school environments link ADHD with academic performance.

Fig. 1

Model of the relationships among symptoms of attention-deficit/hyperactivity disorder (ADHD), reading performance, and mathematics performance. This diagram shows the full model (Model 1), in which the ADHD factor included all four measures of ADHD. The bottom half of the diagram shows the latent factor measurement model, with standardized factor loadings and residuals; the upper half shows an independent pathway model with variances and covariances among the factors decomposed into general and independent genetic (A), shared-environment (C), and nonshared-environment (E) influences. See the text for an explanation of the subscripts. ADHD was measured by the Inattention (In) and Hyperactivity/Impulsivity (H/Im) subscales of The Strength and Weaknesses of ADHD-Symptoms and Normal-Behavior scale (SWAN; Swanson et al., 2005) and by ratings of “attention to tasks” (Att) and “hyperactivity” (Hyp) on the Bayley Behavior Rating Scale (BBR; Bayley, 1993). Reading performance was measured by the Word Identification (Word ID) and Passage Comprehension (PC) subtests of the Woodcock Reading Mastery Tests (WRMT; Woodcock, 1987). Math performance was measured by the Applied Problems (AP), Quantitative Concepts (QC), Fluency, and Calculation (Calc) subtests of the Woodcock-Johnson III (WJ; Woodcock, McGraw, & Mather, 2001). Significant estimates are indicated by asterisks (*p < .05).