Processing Speed is Related to the General Psychopathology Factor in Youth.

The relationship between the p factor and cognition in youth has largely focused on general cognition (IQ) and executive functions (EF). Another cognitive construct, processing speed (PS), is dissociable from IQ and EF, but has received less research attention despite being related to many different mental health symptoms. The present sample included 795 youth, ages 11-16 from the Colorado Learning Disabilities Research Center (CLDRC) sample.

Discovery of 42 genome-wide significant loci associated with dyslexia.

Reading and writing are crucial life skills but roughly one in ten children are affected by dyslexia, which can persist into adulthood. Family studies of dyslexia suggest heritability up to 70%, yet few convincing genetic markers have been found. Here we performed a genome-wide association study of 51,800 adults self-reporting a dyslexia diagnosis and 1,087,070 controls and identified 42 independent genome-wide significant loci: 15 in genes linked to cognitive ability/educational attainment, and 27 new and potentially more specific to dyslexia.

Compounding Effects of Domain-General Cognitive Weaknesses and Word Reading Difficulties on Anxiety Symptoms in Youth.

This study examined whether domain-general cognitive weaknesses in processing speed (PS) or executive functioning (EF) moderate the relation between word reading scores and anxiety such that lower word reading scores in combination with lower cognitive scores are associated with higher anxiety symptoms. The sample consisted of 755 youth ages 8-16 who were recruited as part of the Colorado Learning Disabilities Research Center twins study. Lower scores on PS ( = .

Sequencing Deficits and Phonological Speech Errors, But Not Articulation Errors, Predict Later Literacy Skills.

Purpose: Speech sound disorder (SSD) in conjunction with a language disorder has been associated with poor literacy acquisition; however, no study has evaluated whether articulation, phonological, or sequencing skills are differentially related to reading skills. Therefore, this study examined the relationship between speech error types at ages 5-6 years and literacy at ages 7-9 years. Phonological errors were hypothesized to predict phonological awareness (PA) and literacy even while accounting for other speech error types and language skills.

Mathematics Difficulties and Psychopathology in School-Age Children.

This study investigated the relationship between mathematics difficulties and psychopathology in a large community sample ( = 881) of youth (8-18 years of age) in the United States. The primary aims of the study were to (a) test the associations between mathematics difficulties and specific components of internalizing, externalizing, attention, and social problems; (b) examine potential age and gender differences; and (c) investigate the longitudinal relationship between mathematics and psychopathology using 5-year follow-up data. Results indicated that individuals with mathematics difficulties exhibited elevations in most dimensions of psychopathology, including anxiety, depression, externalizing behaviors, attention problems, and social problems.

Heritability and Clinical Characteristics of Neuropsychological Profiles in Youth With and Without Elevated ADHD Symptoms.

Objective: In the last decade, there has been an increase in research that aims to parse heterogeneity in attention deficit hyperactivity disorder (ADHD). The current study tests heritability of latent class neuropsychological subtypes.

Method: Latent class analysis was used to derive subtypes in a sample of school-age twins ( = 2,564) enriched for elevated ADHD symptoms.

In Search of Cognitive Promotive and Protective Factors for Word Reading.

This study examined whether strong cognitive skills (i.e. vocabulary, rapid naming, verbal working memory [VWM], and processing speed [PS]) contributed to resilience in single-word reading skills in children at risk for reading difficulties because of low phonological awareness scores (PA).

How Specific Are Learning Disabilities?

Despite historical emphasis on "specific" learning disabilities (SLDs), academic skills are strongly correlated across the curriculum. Thus, one can ask how specific SLDs truly are. To answer this question, we used bifactor models to identify variance shared across academic domains (academic ), as well as variance unique to reading, mathematics, and writing.

The Multiple Deficit Model: Progress, Problems, and Prospects.

The multiple deficit model (MDM) was proposed because the prevailing single-deficit model provided an inadequate account of atypical neuropsychological development. Across methods and levels of analysis, there has been support for the two fundamental tenets of the MDM, that multiple predictors contribute probabilistically to neurodevelopmental disorders and shared risk factors contribute to comorbidity. Diagnostically, the multiplicity of factors means that no single cognitive deficit or combination of deficits can be used to rule in or out most neurodevelopmental disorders.

Cross-Country Differences in Parental Reporting of Symptoms of ADHD.

Previous studies within the United States suggest there are cultural and contextual influences on how Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms are perceived. If such influences operate within a single country, they are likely to also occur between countries. In the current study, we tested whether country differences in mean ADHD scores also reflect cultural and contextual differences, as opposed to actual etiological differences.

Understanding Comorbidity Between Specific Learning Disabilities.

Current definitions of specific learning disability (SLD) identify a heterogeneous population that includes individuals with weaknesses in reading, math, or writing, and these academic difficulties often co-occur in many of the same individuals. The Colorado Learning Disabilities Research Center (CLDRC) is an interdisciplinary, multisite research program that uses converging levels of analysis to understand the genetic and environmental etiology, neuropsychology, and developmental outcomes of SLDs in reading (RD), math (MD), and writing (WD), along with the comorbidity between these SLDs and other developmental disorders. The latest results from the CLDRC twin study suggest that shared genetic influences contribute to the significant covariance between all aspects of reading (word reading, reading fluency, and reading comprehension) and math (calculations, math fluency, and word problems), and distinct genetic or environmental influences also contribute to weaknesses in each specific academic domain.

Multivariate genome-wide association study of rapid automatised naming and rapid alternating stimulus in Hispanic American and African-American youth.

Background: Rapid automatised naming (RAN) and rapid alternating stimulus (RAS) are reliable predictors of reading disability. The underlying biology of reading disability is poorly understood. However, the high correlation among RAN, RAS and reading could be attributable to shared genetic factors that contribute to common biological mechanisms.

Genome-wide association scan identifies new variants associated with a cognitive predictor of dyslexia.

Developmental dyslexia (DD) is one of the most prevalent learning disorders, with high impact on school and psychosocial development and high comorbidity with conditions like attention-deficit hyperactivity disorder (ADHD), depression, and anxiety. DD is characterized by deficits in different cognitive skills, including word reading, spelling, rapid naming, and phonology. To investigate the genetic basis of DD, we conducted a genome-wide association study (GWAS) of these skills within one of the largest studies available, including nine cohorts of reading-impaired and typically developing children of European ancestry (N = 2562-3468).

Approximate Number Sense Shares Etiological Overlap with Mathematics and General Cognitive Ability.

Approximate number sense (ANS), the ability to rapidly and accurately compare quantities presented non-symbolically, has been proposed as a precursor to mathematics skills. Earlier work reported low heritability of approximate number sense, which was interpreted as evidence that approximate number sense acts as a fitness trait. However, viewing ANS as a fitness trait is discordant with findings suggesting that individual differences in approximate number sense acuity correlate with mathematical performance, a trait with moderate genetic effects.

Enrichment of putatively damaging rare variants in the DYX2 locus and the reading-related genes CCDC136 and FLNC.

Eleven loci with prior evidence for association with reading and language phenotypes were sequenced in 96 unrelated subjects with significant impairment in reading performance drawn from the Colorado Learning Disability Research Center collection. Out of 148 total individual missense variants identified, the chromosome 7 genes CCDC136 and FLNC contained 19. In addition, a region corresponding to the well-known DYX2 locus for RD contained 74 missense variants.

Literacy acquisition influences children's rapid automatized naming.

Previous research has established that learning to read improves children's performance on reading-related phonological tasks, including phoneme awareness (PA) and nonword repetition. Few studies have investigated whether literacy acquisition also promotes children's rapid automatized naming (RAN). We tested the hypothesis that literacy acquisition should influence RAN in an international, longitudinal population sample of twins.

Explaining the sex difference in dyslexia.

Background: Males are diagnosed with dyslexia more frequently than females, even in epidemiological samples. This may be explained by greater variance in males' reading performance.

Methods: We expand on previous research by rigorously testing the variance difference theory, and testing for mediation of the sex difference by cognitive correlates.

Genetic Etiologies of Comorbidity and Stability for Reading Difficulties and ADHD: A Replication Study.

Because of recent concerns about the replication of published results in the behavioral and biomedical sciences (Ioannidis, PLoS Medicine, Vol. 2, 2005, p. e124; Open Science Collaboration, Science, Vol.

Investigating the effects of copy number variants on reading and language performance.

Background: Reading and language skills have overlapping genetic bases, most of which are still unknown. Part of the missing heritability may be caused by copy number variants (CNVs).

Methods: In a dataset of children recruited for a history of reading disability (RD, also known as dyslexia) or attention deficit hyperactivity disorder (ADHD) and their siblings, we investigated the effects of CNVs on reading and language performance.

Cognitive Prediction of Reading, Math, and Attention: Shared and Unique Influences.

The current study tested a multiple-cognitive predictor model of word reading, math ability, and attention in a community-based sample of twins ages 8 to 16 years ( N = 636). The objective was to identify cognitive predictors unique to each skill domain as well as cognitive predictors shared among skills that could help explain their overlap and thus help illuminate the basis for comorbidity of related disorders (reading disability, math disability, and attention deficit hyperactivity disorder). Results indicated that processing speed contributes to the overlap between reading and attention as well as math and attention, whereas verbal comprehension contributes to the overlap between reading and math.

The regulatory element READ1 epistatically influences reading and language, with both deleterious and protective alleles.

Background: Reading disability (RD) and language impairment (LI) are heritable learning disabilities that obstruct acquisition and use of written and spoken language, respectively. We previously reported that two risk haplotypes, each in strong linkage disequilibrium (LD) with an allele of READ1, a polymorphic compound short tandem repeat within intron 2 of risk gene DCDC2, are associated with RD and LI. Additionally, we showed a non-additive genetic interaction between READ1 and KIAHap, a previously reported risk haplotype in risk gene KIAA0319, and that READ1 binds the transcriptional regulator ETV6.

The Colorado Longitudinal Twin Study of Reading Difficulties and ADHD: Etiologies of Comorbidity and Stability.

Approximately 60% of children with reading difficulties (RD) meet criteria for at least one co-occurring disorder. The most common of these, attention deficit-hyperactivity disorder (ADHD), occurs in 20-40% of individuals with RD. Recent studies have suggested that genetic influences are responsible.