Erik G . Willcutt

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One of the most prominent neuropsychologic theories of attention-deficit/hyperactivity disorder (ADHD) suggests that its symptoms arise from a primary deficit in executive functions (EF), defined as neurocognitive processes that maintain an appropriate problem-solving set to attain a later goal. To examine the validity of the EF theory, we conducted a(More)
This article describes a comprehensive meta-analysis that was conducted to estimate the prevalence of attention-deficit/hyperactivity disorder (ADHD), as defined by the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). A systematic literature review identified 86 studies of children and adolescents (N = 163,688 individuals) and(More)
This study used a nonreferred sample of twins to contrast the performance of individuals with reading disability (RD; n = 93), attention-deficit/hyperactivity disorder (ADHD; n = 52), RD and ADHD (n = 48), and neither RD nor ADHD (n = 121) on measures of phoneme awareness (PA) and executive functioning (EF). Exploratory factor analysis of the EF measures(More)
OBJECTIVE Little is known about the validity of the diagnosis of attention-deficit/hyperactivity disorder (ADHD) in young children. Moreover, the results of the DSM-IV field trials raised concerns that inclusion of the new predominantly hyperactive-impulsive type of ADHD in DSM-IV might increase the likelihood of the diagnosis being given to active but(More)
Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria for attention deficit/hyperactivity disorder (ADHD) specify two dimensions of inattention and hyperactivity-impulsivity symptoms that are used to define three nominal subtypes: predominantly hyperactive-impulsive type (ADHD-H), predominantly inattentive type (ADHD-I), and(More)
This study investigated the association between reading disability (RD) and internalizing and externalizing psychopathology in a large community sample of twins with (N = 209) and without RD (N = 192). The primary goals were to clarify the relation between RD and comorbid psychopathology, to test for gender differences in the behavioral correlates of RD,(More)
This study used a community sample of 494 twins with a reading disability (223 girls, 271 boys) and 373 twins without a reading disability (189 girls, 184 boys) to assess the relation between reading disability (RD) and attention-deficit/hyperactivity disorder (ADHD). Symptoms of DSM-III and DSM-IV ADHD were classified into symptoms of inattention and(More)
INTRODUCTION Attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) are complex childhood disorders that frequently co-occur, but the etiology of this comorbidity remains unknown. METHOD Participants were 457 twin pairs from the Colorado Learning Disabilities Research Center (CLDRC) twin study, an ongoing study of the etiology of RD,(More)
Measures of component reading and language skills, executive functions, and processing speed were administered to groups of children with attention deficit hyperactivity disorder (ADHD; n = 113), reading disability (RD; n = 109), both RD and ADHD (n = 64), and neither RD nor ADHD (n = 151). Groups with RD exhibited pronounced deficits on all measures of(More)
We test our neurocomputational model of fronto-striatal dopamine (DA) and noradrenaline (NA) function for understanding cognitive and motivational deficits in attention deficit/hyperactivity disorder (ADHD). Our model predicts that low striatal DA levels in ADHD should lead to deficits in ‘Go’ learning from positive reinforcement, which should be alleviated(More)