Examining Differences in the Genetic and Functional Architecture of Attention-Deficit/Hyperactivity Disorder Diagnosed in Childhood and Adulthood

Background

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with diagnostic criteria requiring symptoms to begin in childhood. We investigated whether individuals diagnosed as children differ from those diagnosed in adulthood with respect to shared and unique architecture at the genome-wide and gene expression level of analysis.

Methods

We used genomic structural equation modeling (SEM) to investigate differences in genetic correlations (rg) of childhood-diagnosed (ncases = 14,878) and adulthood-diagnosed (ncases = 6961) ADHD with 98 behavioral, psychiatric, cognitive, and health outcomes. We went on to apply transcriptome-wide SEM to identify functional annotations and patterns of gene expression associated with genetic risk sharing or divergence across the ADHD subgroups.

Results

Compared with the childhood subgroup, adulthood-diagnosed ADHD exhibited a significantly larger negative rg with educational attainment, the noncognitive skills of educational attainment, and age at first sexual intercourse. We observed a larger positive rg for adulthood-diagnosed ADHD with major depression, suicidal ideation, and a latent internalizing factor. At the gene expression level, transcriptome-wide SEM analyses revealed 22 genes that were significantly associated with shared genetic risk across the subtypes that reflected a mixture of coding and noncoding genes and included 15 novel genes relative to the ADHD subgroups.

Conclusions

This study demonstrated that ADHD diagnosed later in life shows much stronger genetic overlap with internalizing disorders and related traits. This may indicate the potential clinical relevance of distinguishing these subgroups or increased misdiagnosis for those diagnosed later in life. Top transcriptome-wide SEM results implicated genes related to neuronal function and clinical characteristics (e.g., sleep).

Stimulus shapes strategy: Effects of stimulus characteristics and individual differences in academic achievement on the neural mechanisms engaged during the N-back task

This fMRI study of 126 youth explored whether the neural mechanisms underlying the N-back task, commonly used to examine executive control over the contents of working memory, are associated with individual differences in academic achievement in reading and math. Moreover, the study explored whether these relationships occur regardless of the nature of the stimulus being manipulated in working memory (letters, numbers, nonsense shapes) or whether these relationships are specific to achievement domain and stimulus type (i.e., letters for reading and numbers for math). The results indicated that higher academic achievement in each of reading and math was associated with greater activation of dorsolateral prefrontal cortex in the N-back task regardless of stimulus type (i.e., did not differ for letters and numbers), suggesting that at least some aspects of the neural mechanisms underlying these academic domains are executive in nature. In addition, regardless of level of academic achievement, prefrontal regions were engaged to a greater degree for letters than numbers than nonsense shapes. In contrast, nonsense shapes yielded greater hippocampal activation than letters and numbers. Potential reasons for this pattern of findings are discussed.

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 (R2 = .007, p = .014), EF (R2 = .009, p = .006), and word reading (R2 = .006-.008, p = .010-.032) were associated with higher anxiety scores. In addition, the word reading × cognitive interactions were significant such that lower scores on PS (R2 = .010, p = .005) or EF (R2 = .013, p = .010) combined with lower word reading were associated with higher-than-expected anxiety symptoms. Results suggest that weaknesses in PS, EF, and word reading are modestly associated with higher anxiety symptoms, and these anxiety symptoms may be compounded in youth with both PS or EF weaknesses and word reading difficulties. These findings can guide assessment approaches for identifying youth with word reading challenges who may be at increased risk for anxiety.

The Rosetta Phenotype Harmonization Method Facilitates Finding a Relationship Quantitative Trait Locus for a Complex Cognitive Trait

Genetics researchers increasingly combine data across many sources to increase power and to conduct analyses that cross multiple individual studies. However, there is often a lack of alignment on outcome measures when the same constructs are examined across studies. This inhibits comparison across individual studies and may impact the findings from meta-analysis. Using a well-characterized genotypic (brain-derived neurotrophic factor: BDNF) and phenotypic constructs (working memory and reading comprehension), we employ an approach called Rosetta, which allows for the simultaneous examination of primary studies that employ related but incompletely overlapping data. We examined four studies of BDNF, working memory, and reading comprehension with a combined sample size of 1711 participants. Although the correlation between working memory and reading comprehension over all participants was high, as expected (ρ = 0.45), the correlation between working memory and reading comprehension was attenuated in the BDNF Met/Met genotype group (ρ = 0.18, n.s.) but not in the Val/Val (ρ = 0.44) or Val/Met (ρ = 0.41) groups. These findings indicate that Met/Met carriers may be a unique and robustly defined subgroup in terms of memory and reading comprehension. This study demonstrates the utility of the Rosetta method when examining complex phenotypes across multiple studies, including psychiatric genetic studies, as shown here, and also for the mega-analysis of cohorts generally.

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. Confirmatory factor analyses tested multiple p factor models, with the primary model being a second-order, multi-reporter p factor. We then tested the correlation between the p factor and a latent PS factor. There was a significant, negative correlation between the p factor and PS (r(87) = -0.42, p < .001), indicating that slower processing speed is associated with higher general mental health symptoms. This association is stronger than previously reported associations with IQ or EF. This finding was robust across models that used different raters (youth and caregiver) and modeling approaches (second-order vs. bifactor). Our findings indicate that PS is related to general psychopathology symptoms. This research points to processing speed as an important transdiagnostic construct that warrants further exploration across development.

Report of a Work Group on Sluggish Cognitive Tempo: Key Research Directions and a Consensus Change in Terminology to Cognitive Disengagement Syndrome

OBJECTIVE

The aim of this work was 2-fold: (1) to evaluate current knowledge and identify key directions in the study of sluggish cognitive tempo (SCT); and (2) to arrive at a consensus change in terminology for the construct that reflects the current science and may be more acceptable to researchers, clinicians, caregivers, and patients.

METHOD

An international Work Group was convened that, in early 2021, compiled an online archive of all research studies on SCT and summarized the current state of knowledge, noted methodological issues, and highlighted future directions, and met virtually on 10 occasions in 2021 to discuss these topics and terminology.

RESULTS

Major progress has been made over the last decade in advancing our understanding of SCT across the following domains of inquiry: construct measurement and stability; genetic, environmental, pathophysiologic, and neuropsychological correlates; comorbid conditions; functional impairments; and psychosocial and medication interventions. Findings across these domains are summarized, and potential avenues to pursue in the next generation of SCT-related research are proposed. Following repeated discussions on terminology, the Work Group selected "cognitive disengagement syndrome" (CDS) to replace "SCT" as the name for this construct. This term was deemed to best satisfy considerations that should apply when selecting terms for a condition or syndrome, as it does not overlap with established terms for other constructs, is not offensive, and reflects the current state of the science.

CONCLUSION

It is evident that CDS (SCT) has reached the threshold of recognition as a distinct syndrome. Much work remains to further clarify its nature (eg, transdiagnostic factor, separate disorder, diagnostic specifier), etiologies, demographic factors, relations to other psychopathologies, and linkages to specific domains of functional impairment. Investigators are needed with interests and expertise spanning basic, clinical, and translational research to advance our understanding and to improve the lives of individuals with this unique syndrome.

ADHD and Psychological Need Fulfillment in College Students

OBJECTIVE

Self-determination theory suggests that the satisfaction and frustration of basic psychological needs-autonomy, competence, relatedness-are uniquely associated with overall well-being. Undergraduates with attention-deficit/hyperactivity disorder (ADHD) experience more academic-related impairment and are less likely to graduate. Thus, well-being is important to understand and aim to improve in these students.

METHOD

Students at four universities (N = 2,197) completed a survey and reported previous diagnoses, ADHD symptoms, and psychological need satisfaction and frustration. Group differences were explored via t-tests; associations were explored via structural equation modeling.

RESULTS

The ADHD group reported lower satisfaction and higher frustration across all psychological needs. Inattention and hyperactivity/impulsivity were uniquely associated with aspects of need fulfillment beyond the impact of comorbid symptoms. Sex differences emerged such that women with ADHD had the lowest overall need satisfaction.

CONCLUSIONS

Addressing need fulfillment, both satisfaction and frustration, in interventions with undergraduates with clinical/subclinical levels of ADHD may optimize treatment effectiveness.

Mathematics Difficulties and Psychopathology in School-Age Children

This study investigated the relationship between mathematics difficulties and psychopathology in a large community sample (N = 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. Furthermore, mathematics impairment was associated with internalizing problems, rule-breaking behaviors, inattention, and social problems even after controlling for comorbid reading difficulties. Results suggested that the associations between mathematics and psychopathology are generally similar in males and females. Finally, preliminary longitudinal evidence suggested that initial mathematics difficulties predicted elevations of conduct disorder, rule-breaking behavior, inattention, hyperactivity, and social problems at follow-up, with several of these associations remaining significant even after controlling for initial reading. In contrast, there was no significant association between initial mathematics ability and internalizing symptoms at follow-up, demonstrating some amelioration of internalizing symptoms over time.

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. We validated 23 loci (13 new) in independent cohorts of Chinese and European ancestry. Genetic etiology of dyslexia was similar between sexes, and genetic covariance with many traits was found, including ambidexterity, but not neuroanatomical measures of language-related circuitry. Dyslexia polygenic scores explained up to 6% of variance in reading traits, and might in future contribute to earlier identification and remediation of dyslexia.

The Angular Gyrus as a Hub for Modulation of Language-related Cortex by Distinct Prefrontal Executive Control Regions

It has become clear in recent years that reading, while relying on domain-specific language processing regions, also involves regions that implement executive processes more broadly. Such executive control is generally considered to be implemented by prefrontal regions, which exert control via connectivity that allows them to modulate processing in target brain regions. The present study examined whether three previously identified and distinct executive control regions in the pFC [Wang, K., Banich, M. T., Reineberg, A. E., Leopold, D. R., Willcutt, E. G., Cutting, L. E., et al. Left posterior prefrontal regions support domain-general executive processes needed for both reading and math. Journal of Neuropsychology, 14, 467-495, 2020] show similar patterns of functional connectivity (FC) during a reading comprehension task as compared with a symbol identification condition. Our FC results in a sample of adolescents (n = 120) suggest all three regions commonly show associations with activity in "classic" left hemisphere reading areas, including the angular and supramarginal gyri, yet each exhibits differential connectivity as well. In particular, precentral regions show differential FC to parietal portions of the dorsal language stream, the inferior frontal junction shows differential FC to middle temporal regions of the right hemisphere and other regions involved in semantic processing, and portions of the inferior frontal gyrus show differential FC to an extensive set of right hemisphere prefrontal regions. These results suggest that prefrontal control over language-related regions occurs in a coordinated yet discrete manner.

Genome-wide analyses of individual differences in quantitatively assessed reading- and language-related skills in up to 34,000 people

The use of spoken and written language is a fundamental human capacity. Individual differences in reading- and language-related skills are influenced by genetic variation, with twin-based heritability estimates of 30 to 80% depending on the trait. The genetic architecture is complex, heterogeneous, and multifactorial, but investigations of contributions of single-nucleotide polymorphisms (SNPs) were thus far underpowered. We present a multicohort genome-wide association study (GWAS) of five traits assessed individually using psychometric measures (word reading, nonword reading, spelling, phoneme awareness, and nonword repetition) in samples of 13,633 to 33,959 participants aged 5 to 26 y. We identified genome-wide significant association with word reading (rs11208009, P = 1.098 × 10-8) at a locus that has not been associated with intelligence or educational attainment. All five reading-/language-related traits showed robust SNP heritability, accounting for 13 to 26% of trait variability. Genomic structural equation modeling revealed a shared genetic factor explaining most of the variation in word/nonword reading, spelling, and phoneme awareness, which only partially overlapped with genetic variation contributing to nonword repetition, intelligence, and educational attainment. A multivariate GWAS of word/nonword reading, spelling, and phoneme awareness maximized power for follow-up investigation. Genetic correlation analysis with neuroimaging traits identified an association with the surface area of the banks of the left superior temporal sulcus, a brain region linked to the processing of spoken and written language. Heritability was enriched for genomic elements regulating gene expression in the fetal brain and in chromosomal regions that are depleted of Neanderthal variants. Together, these results provide avenues for deciphering the biological underpinnings of uniquely human traits.

Modeling the Speeded Determinants of Adolescents' Academic and Attentional Functioning

The current study utilized a large, unselected sample of adolescent twins to examine whether processing speed (PS) is an important shared predictor that accounts for covariance among reading, math, ADHD, and rapid naming (RN). The best fitting model included correlated but distinguishable latent measures of PS, RN, reading, math, inattention, hyperactivity/impulsivity, and academic fluency. PS was a shared predictor across all outcomes, while RN was uniquely associated with reading, fluency, and (albeit weakly) math. The results add to a growing literature suggesting that PS and RN may be important components of comprehensive neuropsychological models of academics, ADHD, and their covariation.

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 g), as well as variance unique to reading, mathematics, and writing. Participants were 686 children ages 8 to 16. Although the sample was overselected for learning disabilities, we intentionally included children across the full range of individual differences in this study in response to growing recognition that a dimensional, quantitative view of SLD is more accurate than a categorical view. Confirmatory factor analysis identified five academic domains (basic reading, reading comprehension, basic math, math problem-solving, and written expression); spelling clustered with basic reading and not writing. In the bifactor model, all measures loaded significantly on academic g. Basic reading and mathematics maintained variance distinct from academic g, consistent with the notion of SLDs in these domains. Writing did not maintain specific variance apart from academic g, and evidence for reading comprehension-specific variance was mixed. Academic g was strongly correlated with cognitive g (r = .72) but not identical to it. Implications for SLD diagnosis are discussed.

Unique considerations in the assessment of ADHD in college students

Evidence-based practice in psychology (EBPP) has long focused on treatment, but evidence-based psychological assessment (EBPA) is also crucial given the important role of accurate and reliable diagnostic practices in treatment planning. In terms of the diagnosis of attention-deficit/hyperactivity disorder (ADHD), EBPA practices are well-established for children, and more recently for adults, but for college students in particular there are special considerations that warrant attention. College students with symptoms of ADHD have some challenges that are unique, and thus the assessment and diagnosis of ADHD in these students is unique. The aim of this review is not to cover all EBPA strategies for diagnosing ADHD in emerging adult college students; rather, we will focus on the unique considerations at play in college ADHD assessment. These include (a) conceptual matters such as the appropriateness of the DSM-5 criteria for college students, the limitations of our understanding of ADHD this population because of a lack of diversity in research studies, and the issue of late-identified ADHD; and (b) practical matters, such as specific documentation needs, how to gather and interpret self- and other-report of symptoms, how to assess impairment, and alternate explanations for ADHD-like symptoms in college students.

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). Promotive factors were identified by main effects and protective factors through PA x cognition interactions. This study included 1,807 children ages 8-16. As predicted, all cognitive skills were significantly related to reading, consistent with promotive effects. A significant, but small effect PA x vocabulary interaction (R2 change=.002, p=.00038) was detected but its form was not consistent with a classic protective effect. Rather, the PA x vocabulary interaction was consistent with a "skill-enhancement" pattern, such that children with strong PA and vocabulary skills had better than expected reading. This study provides a framework for reading resilience research and directs attention to promotive mechanisms underlying reading success.

Invariance of ADHD Symptoms Across Sex and Age: a Latent Analysis of ADHD and Impairment Ratings from Early Childhood into Adolescence

A population-based longitudinal sample of 489 twin pairs was assessed at six time points over ten years to examine the measurement invariance and stability of attention-deficit/hyperactivity disorder (ADHD) symptoms, as well as the developmental relations between inattention (IN), hyperactivity-impulsivity (HI), and multiple aspects of functional impairment. Parent ratings of ADHD symptoms and functional impairment were obtained in preschool and after the completion of kindergarten, first, second, fourth, and ninth grades. Results of the temporal and sex invariance models indicated that parent ratings of the 18 ADHD symptoms function in the same manner for females and males from early childhood into adolescence. In addition to establishing this prerequisite condition for the interpretation of longitudinal and between-sex differences in the IN and HI symptom dimensions, cross-lagged models indicated that both IN and HI were associated with increased risk for both concurrent and future overall, social, and recreational impairment, whereas only IN was uniquely associated with later academic impairment. Taken together, the current results demonstrate that IN and HI are highly stable from preschool through ninth grade, invariant between females and males, and indicative of risk for impairment in multiple areas, thereby providing strong support for the validity of the symptom dimensions among both sexes.

Behavior and Molecular Genetic Approaches to Comorbidity

Purpose of Review

This review provides an overview of studies that used behavioral genetic methods to understand the genetic and environmental influences that lead to comorbidity, the co-occurrence of two or more developmental disorders in the same individual.

Recent Findings

Comorbidity is primarily explained by shared genetic influences for most pairs of disorders that have been studied, including attention deficit hyperactivity disorder (ADHD) and learning disabilities, conduct disorder and ADHD, anxiety and depression, and anxiety and autism spectrum disorder (ASD). Molecular genetic studies indicate that the etiologies of developmental disorders are highly multifactorial, with dozens or even hundreds of genes acting in combination with environmental risk factors to lead to each individual disorder and the extensive comorbidity between disorders. Due to this complexity, current state-of-the-art studies are now combining molecular genetic data from multiple large samples to begin to achieve adequate statistical power to identify the specific genetic polymorphisms that lead to comorbidity.

Summary

An extensive literature demonstrates the pervasiveness and potential importance of comorbidity between developmental disorders, and results of family, twin, and molecular genetic studies indicate that these comorbidities may be largely explained by shared genetic influences. Additional studies are ongoing to identify the specific genetic polymorphisms that increase risk for each developmental disorder and comorbidity between disorders.

Left posterior prefrontal regions support domain-general executive processes needed for both reading and math

Substantial evidence has suggested that reading and math are supported by executive processes (EP). However, to date little is known about which portion of the neural system underpinning domain-general executive skills works to support reading and math. In this study, we aimed to answer this question using fMRI via two complementary approaches. First, imaging data were acquired whilst a sample of 231 adolescents performed each of three separate tasks designed to assess reading comprehension, numerical magnitude estimation, and EP in working memory (WM), respectively. With careful task designs and conjunction analyses, we were able to isolate cross-domain brain activity specifically related to EP, as opposed to lower-level domain-general processes (e.g., visual processing). Second, the meta-analytic tool Neurosynth was used to independently identify brain regions involved reading, math, and EP. Using a combination of forward and reverse statistical inference and conjunction analyses, we again isolated brain regions specifically supporting domain-general EP. Results from both approaches yielded overlapping activation for reading, math, and EP in the left ventrolateral prefrontal cortex, left inferior frontal junction, and left precentral gyrus. This pattern suggests that posterior regions of the prefrontal cortex, rather than more central regions such as mid-DLPFC, play a leading role in supporting domain-general EP utilized by both reading and math.

DSM-5 and Other Symptom Thresholds for ADHD: Which Is the Best Predictor of Impairment in College Students?

OBJECTIVE

Approximately 5% of adults have ADHD. Despite recommendations regarding the diagnosis of emerging adults, there is not a strong consensus regarding the ideal method for diagnosing ADHD in both emerging and mature adults. We were interested in determining whether a threshold of four, five, or six ADHD symptoms would be associated with significantly different levels of functional impairment and be more or less indicative of a potential ADHD diagnosis.

METHOD

We examined the relation between functional impairment and these ADHD symptom thresholds in 2,577 college students.

RESULTS

Our findings suggest that none of these symptom thresholds are differentially better at predicting functional impairment.

CONCLUSION

The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) threshold of five symptoms for ages 17 years and older is not necessarily predictive of ADHD-related impairment in college students and may not be preferable to other thresholds. Options for resolving this diagnostic dilemma are discussed.

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.

OBJECTIVE

To identify shared genetic factors that contribute to RAN and RAS performance using a multivariate approach.

METHODS

We conducted a multivariate genome-wide association analysis of RAN Objects, RAN Letters and RAS Letters/Numbers in a sample of 1331 Hispanic American and African-American youth. Follow-up neuroimaging genetic analysis of cortical regions associated with reading ability in an independent sample and epigenetic examination of extant data predicting tissue-specific functionality in the brain were also conducted.

RESULTS

Genome-wide significant effects were observed at rs1555839 (p=4.03×10-8) and replicated in an independent sample of 318 children of European ancestry. Epigenetic analysis and chromatin state models of the implicated 70 kb region of 10q23.31 support active transcription of the gene RNLS in the brain, which encodes a catecholamine metabolising protein. Chromatin contact maps of adult hippocampal tissue indicate a potential enhancer-promoter interaction regulating RNLS expression. Neuroimaging genetic analysis in an independent, multiethnic sample (n=690) showed that rs1555839 is associated with structural variation in the right inferior parietal lobule.

CONCLUSION

This study provides support for a novel trait locus at chromosome 10q23.31 and proposes a potential gene-brain-behaviour relationship for targeted future functional analysis to understand underlying biological mechanisms for reading disability.

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. The sample for the present study included 974 participants from four countries tested at two-time points, the end of preschool and the end of 2^nd grade. Consistent with previous research, we found lower mean ADHD scores in Norway and Sweden in comparison to Australia and the United States, and we tested four explanations for these country differences: 1) Genuine etiological differences, 2) Slower introduction to formal academic skills in Norway and Sweden than in the United States and Australia that indicated a context difference, 3) Under-reporting tendency in Norway and Sweden, or 4) Over-reporting tendency in the United States and Australia. Either under-or over-reporting would be examples of cultural differences in the perception of ADHD symptoms. Of these explanations, results of ADHD measurement equivalence tests across countries rejected the first three explanations and supported the fourth explanation: an over-reporting tendency in the United States and Australia. These findings indicate that parental reporting of ADHD symptoms is more accurate in Norway and Sweden than in Australia and the United States, and thus have important clinical and educational implications for how parental reporting informs an ADHD diagnosis in these countries.

Characterizing and decomposing the neural correlates of individual differences in reading ability among adolescents with task-based fMRI

To better characterize the neural correlates of the full spectrum of reading ability, this fMRI study examined how variations in reading ability correlate with task-based brain activity during reading among a large community sample of adolescents (N = 234). In addition, complimentary approaches taking advantage of empirical as well as independent meta-analytic information were employed to isolate neural substrates of domain-general executive processes that are predictive of reading ability. Age-related differences in brain activity were also examined. Better reading was associated with increased activation in left anterior and inferior temporal regions and parts of orbitofrontal cortex, along with reduced activation in the thalamus and left frontal eye field (FEF). Converging evidence suggests that FEF activity corresponds to executive processes during reading. In contrast, activity in temporal regions is likely to reflect cognitive processes specific to reading. Older adolescents also demonstrated increased activation in an orbitofrontal region that overlaps with the aforementioned age-independent, reading-related regions, along with reduced activity in parietal and occipital regions. These results suggest that comparedto poor readers, proficient readers benefit from efficient reading-specific processes and require less executive effort, implemented via the FEF, during a reading comprehension task.

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. RD and MD are associated with a range of negative outcomes on both concurrent measures and measures of functional outcomes completed 5 years after the twins were first assessed. Over the next several years the CLDRC will continue to expand on this work by administering a comprehensive test battery that includes measures of all dimensions of academic achievement that are described in current definitions of SLD and incorporating these measures in new neuroimaging and molecular genetic studies.

Advancing the study of sluggish cognitive tempo via DSM, RDoC, and hierarchical models of psychopathology

Sluggish cognitive tempo (SCT) is separable from attention-deficit/hyperactivity disorder (ADHD) and other psychopathologies, and growing evidence demonstrates SCT to be associated with impairment in both children and adults. However, it remains unclear how SCT should optimally be conceptualized. In this article, we argue that multiple models of psychopathology should be leveraged to make substantive advances to our understanding of SCT. Both categorical and dimensional approaches should be used, including the Diagnostic and Statistical Manual of Mental Disorders (DSM) nosology, the Research Domain Criteria (RDoC) initiative, and hierarchical models of psychopathology. Studies are needed to determine whether individuals categorized with SCT can be reliably identified and differentiated from individuals without SCT in pathophysiological, neuropsychological, behavioral, and daily life functioning. Studies are also needed to evaluate the validity and utility of SCT as a transdiagnostic and dimensional construct. In considering SCT as a dimensional and potentially transdiagnostic construct, we describe ways in which SCT might be examined within the RDoC framework, including negative valence systems, cognitive systems, and arousal/regulatory systems, as well as within hierarchical models of psychopathology. Conceptualizing SCT within both categorical and dimensional models of psychopathology will help to better understand the causes, developmental pathways, and clinical implications of SCT, both as a construct in its own right and also in relation to other psychopathologies.

Are Sluggish Cognitive Tempo, ADHD, and Oppositional Defiant Disorder Trait- or State-Like Constructs from Prekindergarten to Fourth Grade?

The objective was to determine the proportion of trait (consistency across occasions) and occasion-specific variance in sluggish cognitive tempo (SCT), attention deficit/hyperactivity disorder (ADHD)-inattention (IN), ADHD-hyperactivity/impulsivity (HI), and oppositional defiant disorder (ODD) symptom ratings. A single trait factor-multiple state factors model was applied to parent ratings of SCT, ADHD-IN, ADHD-HI, and ODD symptoms for 978 children (50% female) across prekindergarten (M = 4.90 years), kindergarten (M = 6.27 years), 1st-grade (M = 7.42 years), 2nd-grade (M = 8.45 years), and 4th-grade (M = 10.45 years) assessments. For the prekindergarten assessment, SCT, ADHD-IN, ADHD-HI, and ODD contained more occasion-specific than trait variance (54%, 64%, 56%, and 55% occasion-specific variance, respectively). In contrast, SCT, ADHD-IN, ADHD-HI, and ODD contained more trait than occasion-specific variance for the kindergarten through 4th-grade assessments (62%-72%, 65%-68%, 71%-75%, and 60%-69% trait variance, respectively). SCT, ADHD-IN, ADHD-HI, and ODD are slightly to moderately more state-like than trait-like during the prekindergarten developmental period but are more stable traits than fluctuating states from kindergarten to 4th grade. Findings indicate that, particularly after children start formal schooling, these psychopathology dimensions are primarily stable traits; implications for assessment are discussed.

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). We observed a genome-wide significant effect (p < 1 × 10-8) on rapid automatized naming of letters (RANlet) for variants on 18q12.2, within MIR924HG (micro-RNA 924 host gene; rs17663182 p = 4.73 × 10-9), and a suggestive association on 8q12.3 within NKAIN3 (encoding a cation transporter; rs16928927, p = 2.25 × 10-8). rs17663182 (18q12.2) also showed genome-wide significant multivariate associations with RAN measures (p = 1.15 × 10-8) and with all the cognitive traits tested (p = 3.07 × 10-8), suggesting (relational) pleiotropic effects of this variant. A polygenic risk score (PRS) analysis revealed significant genetic overlaps of some of the DD-related traits with educational attainment (EDUyears) and ADHD. Reading and spelling abilities were positively associated with EDUyears (p ~ [10-5-10-7]) and negatively associated with ADHD PRS (p ~ [10-8-10-17]). This corroborates a long-standing hypothesis on the partly shared genetic etiology of DD and ADHD, at the genome-wide level. Our findings suggest new candidate DD susceptibility genes and provide new insights into the genetics of dyslexia and its comorbities.

Differential impact of trait sluggish cognitive tempo and ADHD inattention in early childhood on adolescent functioning

BACKGROUND

Sluggish cognitive tempo (SCT) is distinct from attention-deficit/hyperactivity disorder inattention (ADHD-IN) and concurrently associated with a range of impairment domains. However, few longitudinal studies have examined SCT as a longitudinal predictor of adjustment. Studies to date have all used a relatively short longitudinal time span (6 months to 2 years) and only rating scale measures of adjustment. Using a prospective, multi-method design, this study examined whether SCT and ADHD-IN were differentially associated with functioning over a 10-year period between preschool and the end of ninth grade.

METHODS

Latent state-trait modeling determined the trait variance (i.e. consistency across occasions) of SCT and ADHD-IN across four measurement points (preschool and the end of kindergarten, first grade, and second grade) in a large population-based longitudinal sample (N = 976). Regression analyses were used to examine trait SCT and ADHD-IN factors in early childhood as predictors of functioning at the end of ninth grade (i.e. parent ratings of psychopathology and social/academic functioning, reading and mathematics academic achievement scores, processing speed and working memory).

RESULTS

Both SCT and ADHD-IN contained more trait variance (Ms = 65% and 61%, respectively) than occasion-specific variance (Ms = 35% and 39%) in early childhood, with trait variance increasing as children progressed from preschool through early elementary school. In regression analyses: (a) SCT significantly predicted greater withdrawal and anxiety/depression whereas ADHD-IN did not uniquely predict these internalizing domains; (b) ADHD-IN uniquely predicted more externalizing behaviors whereas SCT uniquely predicted fewer externalizing behaviors; (c) SCT uniquely predicted shyness whereas both SCT and ADHD-IN uniquely predicted global social difficulties; and (d) ADHD-IN uniquely predicted poorer math achievement and slower processing speed whereas SCT more consistently predicted poorer reading achievement.

CONCLUSIONS

Findings of this study - from the longest prospective sample to date - provide the clearest evidence yet that SCT and ADHD-IN often differ when it comes to the functional outcomes they predict.

A Cognitive Dimensional Approach to Understanding Shared and Unique Contributions to Reading, Math, and Attention Skills

Disorders of reading, math, and attention frequently co-occur in children. However, it is not yet clear which cognitive factors contribute to comorbidities among multiple disorders and which uniquely relate to one, especially because they have rarely been studied as a triad. Thus, the present study considers how reading, math, and attention relate to phonological awareness, numerosity, working memory, and processing speed, all implicated as either unique or shared correlates of these disorders. In response to findings that the attributes of all three disorders exist on a continuum rather than representing qualitatively different groups, this study employed a dimensional approach. Furthermore, we used both timed and untimed academic variables in addition to attention and activity level variables. The results supported the role of working memory and phonological awareness in the overlap among reading, math, and attention, with a limited role of processing speed. Numerosity was related to the comorbidity between math and attention. The results from timed variables and activity level were similar to those from untimed and attention variables, although activity level was less strongly related to cognitive and academic/attention variables. These findings have implications for understanding cognitive deficits that contribute to comorbid reading disability, math disability, and/or attention-deficit/hyperactivity disorder.

Achievement attributions are associated with specific rather than general learning delays

The causal attributions that children make for success and failure have been associated with later reading motivation and ability perceptions, which have the potential to impact future task engagement. Few studies have investigated whether such attributions are domain specific, that is linked with the specific skill in question, or a general motivational set. Even fewer studies have examined these relationships among diverse racial and ethnic subgroups. The present study examined differences in success and failure attributions among children with and without reading delay (RD) and general language impairments (LI), in a predominately Hispanic and African American sample. Participants were 1311 children, 8 to 15 years old. Significant differences in ability attributions were observed between participants with and without RD and LI, with no additive effect for cases with co-occurring reading and language impairments. When reading and vocabulary were evaluated continuously, significant and substantial positive relationships were observed between skill and ability attributions in situations of success, and negative associations observed in situations of failure. Weaker relationships were observed for vocabulary, though vocabulary did function as a moderator in the relationship between reading skill and ability attributions, with stronger associations at higher vocabulary levels. Overall, the findings suggest that ability attributions for reading success and failure are linked with reading skill and/or deficits, and not with general language impairments.

Sluggish cognitive tempo in adults: Psychometric validation of the Adult Concentration Inventory

[Correction Notice: An Erratum for this article was reported in Vol 30(3) of Psychological Assessment (see record 2017-30273-001). In the article, the Table 1 item content was incorrectly ordered. The table, as well as text referencing Table 1 in the Results and Discussion, have been corrected in all versions of this article.] As interest in sluggish cognitive tempo (SCT) increases, a primary limitation for the field is the lack of a unified set of symptoms for assessing SCT. No existing SCT measure includes all items identified in a recent meta-analysis as optimal for distinguishing between SCT and attention-deficit/hyperactivity disorder (ADHD) inattention. This study evaluates a new self-report measure for assessing SCT in adulthood, the Adult Concentration Inventory (ACI), which was developed in response to the meta-analytic findings for assessing SCT. Using a large, multiuniversity sample (N = 3,172), we evaluated the convergent and discriminant validity and reliability of the ACI. We also evaluated the ACI measure of SCT in relation to self-reported demographic characteristics, daily life executive functioning, socioemotional adjustment (i.e., anxiety/depression, loneliness, emotion dysregulation, self-esteem), and functional impairment. Exploratory confirmatory factor analyses resulted in 10 ACI items demonstrating strong convergent and discriminant validity from both anxiety/depressive and ADHD inattentive symptom dimensions. SCT was moderately to-strongly correlated with daily life EF deficits, poorer socioemotional adjustment, and greater global functional impairment. Moreover, SCT remained uniquely associated in structural regression analyses with most of these external criterion domains above and beyond ADHD. Finally, when internalizing symptoms were also covaried, SCT, but not ADHD inattention, remained significantly associated with poorer socioemotional adjustment. These findings support the use of the ACI in future studies examining SCT in adulthood and make a major contribution in moving the field toward a unified set of SCT items that can be used across studies. (PsycINFO Database Record

Reading-Related Causal Attributions for Success and Failure: Dynamic Links With Reading Skill

The present study investigated the relation among reading skills and attributions, naming speed, and phonological awareness across a wide range of reading skill. Participants were 1,105 school-age children and youths from two understudied populations: African Americans and Hispanic Americans. Individual assessments of children ranging in age from 8 to 15 years were conducted for reading outcomes, cognitive and linguistic predictors of reading, and attributions for success and failure in reading situations. Quantile regressions were formulated to estimate these relations across the full skill span of each outcome. Reading-related attributions predicted contextual word recognition, sight word and decoding fluency, and comprehension skills. Attributions to ability in success situations were positively related to each outcome across the full span. On three reading outcomes, this relation strengthened at higher skill levels. Attributions to effort in success situations were consistently and negatively related to all reading outcomes. The results provide evidence that the strength of the relation between reading and attributions varies according to reading skill levels, with the strongest evidence for ability-based attributions in situations of reading success.

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. Both allele sets were filtered for a minor allele frequency ≤0.01 and high Polyphen-2 scores. To determine if observations of these alleles are occurring more frequently in our cases than expected by chance in aggregate, counts from our sample were compared to the number of observations in the European subset of the 1000 Genomes Project using Fisher's exact test. Significant P values were achieved for both CCDC136/FLNC (P = 0.0098) and the DYX2 locus (P = 0.012). Taken together, this evidence further supports the influence of these regions on reading performance. These results also support the influence of rare variants in reading disability.

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. Importantly, the shared etiology of approximate number sense, mathematics, and general cognitive ability has remained unexamined. Thus, the etiology of approximate number sense and its overlap with math and general cognitive ability was assessed in the current study with two independent twin samples (N = 451 pairs). Results suggested that ANS acuity had moderate but significant additive genetic influences. ANS also had overlap with generalist genetic mechanisms accounting for variance and covariance in mathematics and general cognitive ability. Furthermore, ANS may have genetic factors unique to covariance with mathematics beyond overlap with general cognitive ability. Evidence across both samples was consistent with the proposal that the etiology of approximate number sense functions similar to that of mathematics and general cognitive skills.

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. We developed an analytic framework that can be applied to group differences in any psychiatric disorder.

RESULTS

Males' overrepresentation in the low performance tail of the reading distribution was accounted for by mean and variance differences across sex. There was no sex difference at the high performance tail. Processing speed (PS) and inhibitory control partially mediated the sex difference. Verbal reasoning emerged as a strength in males.

CONCLUSIONS

Our results complement a previous finding that PS partially mediates the sex difference in symptoms of attention deficit/hyperactivity disorder (ADHD), and helps explain the sex difference in both dyslexia and ADHD and their comorbidity.

Distinct influences of affective and cognitive factors on children's non-verbal and verbal mathematical abilities

Individual differences in children's math performance have been associated with math anxiety, attention problems, working memory (WM), and reading skills, but the mechanisms by which these factors jointly contribute to children's math achievement are unknown. Here, we use structural equation modeling to characterize the relation between these factors and their influence on non-verbal Numerical Operations (NO) and verbal Math Reasoning (MR) in 330 children (M=8.34years). Our findings indicate that WM plays a central role in both non-verbal NO and verbal MR, whereas math anxiety and reading comprehension have unique and more pronounced influences on MR, compared to NO. Our study elucidates how affective and cognitive factors distinctly influence non-verbal and verbal mathematical problem solving.

Does the Environment Have an Enduring Effect on ADHD? A Longitudinal Study of Monozygotic Twin Differences in Children

Environmental factors play a key role in the development of Attention-Deficit/Hyperactivity Disorder (ADHD), but the long-term effects of these factors are still unclear. This study analyses data from 1024 monozygotic (identical) twins in Australia, the United States, and Scandinavia who were assessed for ADHD in Preschool, Kindergarten, Grade 1, and Grade 2. Differences within each twin pair were used as a direct measure of non-shared environmental effects. The Trait-State-Occasion (TSO) model developed by Cole et al. (Psychological Methods, 10, 3-20, 2005) was used to separate the non-shared environmental effects into stable factors, and transient factors that excluded measurement error. Stable factors explained, on average, 44 % and 39 % of the environmental variance in hyperactive-impulsive and inattentive symptoms, respectively. Transient effects explained the remaining 56 % and 60 % of variance. The proportion of stable variance was higher than expected based on previous research, suggesting promise for targeted interventions if future research identifies these stable risk factors.

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. There was no evidence that executive functioning skills help account for covariation among these skill domains. Instead, specific executive functions differentially related to certain outcomes (i.e., working memory to math and inhibition to attention). We explored whether the model varied in younger versus older children and found only minor differences. Results are interpreted within the context of the multiple deficit framework for neurodevelopmental disorders.

Attention-deficit/hyperactivity disorder and sluggish cognitive tempo throughout childhood: temporal invariance and stability from preschool through ninth grade

BACKGROUND

Although multiple cross-sectional studies have shown symptoms of sluggish cognitive tempo (SCT) and attention-deficit/hyperactivity disorder (ADHD) to be statistically distinct, studies have yet to examine the temporal stability and measurement invariance of SCT in a longitudinal sample. To date, only six studies have assessed SCT longitudinally, with the longest study examining SCT over a 2-year period. The overall goals of this study were to assess the 10-year longitudinal stability and interfactor relationships of ADHD and SCT symptoms among a community sample of children.

METHODS

Confirmatory factor analysis was used to assess the temporal invariance of ADHD and SCT symptoms in a large population-based longitudinal sample (International Longitudinal Twin Study of Early Reading Development) that included children assessed at preschool and after kindergarten, first, second, fourth, and ninth grades (n = 489). Latent autoregressive models were then estimated to assess the stability of these constructs.

RESULTS

Results demonstrated invariance of item loadings and intercepts from preschool through ninth grades, as well as invariance of interfactor correlations. Results further indicated that both ADHD and SCT are highly stable across these years of development, that these symptom dimensions are related but also separable, and that hyperactivity/impulsivity and SCT are both more strongly correlated with inattention than with each other and show differential developmental trajectories. Specifically, even in the presence of latent simplex analyses providing support for the developmental stability of these dimensions, linear comparisons indicated that that mean levels of hyperactivity/impulsivity decreased with time, inattentive ratings were generally stable, and SCT tended to increase slightly across development.

CONCLUSIONS

This study adds to the current literature by being the first to systematically assess and demonstrate the temporal invariance and stability of ADHD and SCT across a span of 10 years.

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. First, we called CNVs with PennCNV using signal intensity data from Illumina OmniExpress arrays (~723,000 probes). Then, we computed the correlation between measures of CNV genomic burden and the first principal component (PC) score derived from several continuous reading and language traits, both before and after adjustment for performance IQ. Finally, we screened the genome, probe-by-probe, for association with the PC scores, through two complementary analyses: we tested a binary CNV state assigned for the location of each probe (i.e., CNV+ or CNV-), and we analyzed continuous probe intensity data using FamCNV.

RESULTS

No significant correlation was found between measures of CNV burden and PC scores, and no genome-wide significant associations were detected in probe-by-probe screening. Nominally significant associations were detected (p~10(-2)-10(-3)) within CNTN4 (contactin 4) and CTNNA3 (catenin alpha 3). These genes encode cell adhesion molecules with a likely role in neuronal development, and they have been previously implicated in autism and other neurodevelopmental disorders. A further, targeted assessment of candidate CNV regions revealed associations with the PC score (p~0.026-0.045) within CHRNA7 (cholinergic nicotinic receptor alpha 7), which encodes a ligand-gated ion channel and has also been implicated in neurodevelopmental conditions and language impairment. FamCNV analysis detected a region of association (p~10(-2)-10(-4)) within a frequent deletion ~6 kb downstream of ZNF737 (zinc finger protein 737, uncharacterized protein), which was also observed in the association analysis using CNV calls.

CONCLUSIONS

These data suggest that CNVs do not underlie a substantial proportion of variance in reading and language skills. Analysis of additional, larger datasets is warranted to further assess the potential effects that we found and to increase the power to detect CNV effects on reading and language.

Extending the 'cross-disorder' relevance of executive functions to dimensional neuropsychiatric traits in youth

BACKGROUND

Evidence that different neuropsychiatric conditions share genetic liability has increased interest in phenotypes with 'cross-disorder' relevance, as they may contribute to revised models of psychopathology. Cognition is a promising construct for study; yet, evidence that the same cognitive functions are impaired across different forms of psychopathology comes primarily from separate studies of individual categorical diagnoses versus controls. Given growing support for dimensional models that cut across traditional diagnostic boundaries, we aimed to determine, within a single cohort, whether performance on measures of executive functions (EFs) predicted dimensions of different psychopathological conditions known to share genetic liability.

METHODS

Data are from 393 participants, ages 8-17, consecutively enrolled in the Longitudinal Study of Genetic Influences on Cognition (LOGIC). This project is conducting deep phenotyping and genomic analyses in youth referred for neuropsychiatric evaluation. Using structural equation modeling, we examined whether EFs predicted variation in core dimensions of the autism spectrum disorder, bipolar illness, and schizophrenia (including social responsiveness, mania/emotion regulation, and positive symptoms of psychosis, respectively).

RESULTS

We modeled three cognitive factors (working memory, shifting, and executive processing speed) that loaded on a second-order EF factor. The EF factor predicted variation in our three target traits, but not in a negative control (somatization). Moreover, this EF factor was primarily associated with the overlapping (rather than unique) variance across the three outcome measures, suggesting that it related to a general increase in psychopathology symptoms across those dimensions.

CONCLUSIONS

Findings extend support for the relevance of cognition to neuropsychiatric conditions that share underlying genetic risk. They suggest that higher-order cognition, including EFs, relates to the dimensional spectrum of each of these disorders and not just the clinical diagnoses. Moreover, results have implications for bottom-up models linking genes, cognition, and a general psychopathology liability.

The Internal, External, and Diagnostic Validity of Sluggish Cognitive Tempo: A Meta-Analysis and Critical Review

OBJECTIVE

To conduct the first meta-analysis evaluating the internal and external validity of the sluggish cognitive tempo (SCT) construct as related to or distinct from attention-deficit/hyperactivity disorder (ADHD) and as associated with functional impairment and neuropsychological functioning.

METHOD

Electronic databases were searched through September 2015 for studies examining the factor structure and/or correlates of SCT in children or adults. The search procedures identified 73 papers. The core SCT behaviors included across studies, as well as factor loadings and reliability estimates, were reviewed to evaluate internal validity. Pooled correlation effect sizes using random effects models were used to evaluate SCT in relation to external validity domains (i.e., demographics, other psychopathologies, functional impairment, and neuropsychological functioning).

RESULTS

Strong support was found for the internal validity of the SCT construct. Specifically, across factor analytic studies including more than 19,000 individuals, 13 SCT items loaded consistently on an SCT factor as opposed to an ADHD factor. Findings also support the reliability (i.e., internal consistency, test-retest reliability, interrater reliability) of SCT. In terms of external validity, there is some indication that SCT may increase with age (r = 0.11) and be associated with lower socioeconomic status (r = 0.10). Modest (potentially negligible) support was found for SCT symptoms being higher in males than females in children (r = 0.05) but not in adults. SCT is more strongly associated with ADHD inattention (r = 0.63 in children, r = 0.72 in adults) than with ADHD hyperactivity-impulsivity (r = 0.32 in children, r = 0.46 in adults), and it likewise appears that SCT is more strongly associated with internalizing symptoms than with externalizing symptoms. SCT is associated with significant global, social, and academic impairment (r = 0.38-0.44). Effects for neuropsychological functioning are mixed, although there is initial support for SCT being associated with processing speed, sustained attention, and metacognitive deficits.

CONCLUSION

This meta-analytic review provides strong support for the internal validity of SCT and preliminary support for the external validity of SCT. In terms of diagnostic validity, there is currently not enough evidence to describe SCT in diagnostic terms. Key directions for future research are discussed, including evaluating the conceptualization of SCT as a transdiagnostic construct and the need for longitudinal research.

Development in reading and math in children from different SES backgrounds: the moderating role of child temperament

Socioeconomic risks (SES risks) are robust risk factors influencing children's academic development. However, it is unclear whether the effects of SES on academic development operate universally in all children equally or whether they vary differentially in children with particular characteristics. The current study aimed to explore children's temperament as protective or risk factors that potentially moderate the associations between SES risks and academic development. Specifically, latent growth modeling (LGM) was used in two longitudinal datasets with a total of 2236 children to examine how family SES risks and children's temperament interactively predicted the development of reading and math from middle childhood to early adolescence. Results showed that low negative affect, high effortful control, and low surgency mitigated the negative associations between SES risks and both reading and math development in this developmental period. These findings underline the heterogeneous nature of the negative associations between SES risks and academic development and highlight the importance of the interplay between biological and social factors on individual differences in development.

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.

Objective

To examine the hypothesis that READ1 is a transcriptional regulator of KIAA0319.

Methods

We characterised associations between READ1 alleles and RD and LI in a large European cohort, and also assessed interactions between READ1 and KIAHap and their effect on performance on measures of reading, language and IQ. We also used family-based data to characterise the genetic interaction, and chromatin conformation capture (3C) to investigate the possibility of a physical interaction between READ1 and KIAHap.

Results and conclusions

READ1 and KIAHap show interdependence—READ1 risk alleles synergise with KIAHap, whereas READ1 protective alleles act epistatically to negate the effects of KIAHap. The family data suggest that these variants interact in trans genetically, while the 3C results show that a region of DCDC2 containing READ1 interacts physically with the region upstream of KIAA0319. These data support a model in which READ1 regulates KIAA0319 expression through KIAHap and in which the additive effects of READ1 and KIAHap alleles are responsible for the trans genetic interaction.

Sex differences in ADHD symptom severity

BACKGROUND

Males show higher rates of attention deficit hyperactivity disorder (ADHD) than do females. Potential explanations include genuine etiological differences or artifact.

METHODS

2,332 twin and sibling youth participated in behavioral and cognitive testing. Partially competing models of symptom severity distribution differences, the mean difference, and variance difference models, were tested within a randomly selected subsample. The Delta method was used to test for mediation of sex differences in ADHD symptom severity by processing speed, inhibition and working memory.

RESULTS

The combined mean difference and variance difference models fully explained the sex difference in ADHD symptom severity. Cognitive endophenotypes mediated 14% of the sex difference effect.

CONCLUSIONS

The sex difference in ADHD symptom severity is valid and may be due to differing genetic and cognitive liabilities between the sexes.

Evaluating the construct validity of adult ADHD and SCT among college students: a multitrait-multimethod analysis of convergent and discriminant validity

OBJECTIVE

To advance our understanding of adult ADHD and sluggish cognitive tempo (SCT), the present study investigates their construct validity by exploring the nature of trait- and method-related variance in self- and parent-ratings of ADHD and SCT.

METHOD

Using a multitrait-multimethod (MTMM) design, response variance in college undergraduates' (n = 3,925) and a subset of their parents' (n = 2,242) ratings was decomposed into method, trait, and error-specific variance.

RESULTS

Global evidence for convergent and discriminant validity was supported, but parameter-level comparisons suggest that method effects, situational specificity, and ADHD's core feature--inattention--are prominent.

CONCLUSION

This investigation offers two important conclusions: (a) SCT appears to be a related but separate factor from ADHD; and (b) self- and parent-ratings of emerging adult ADHD exhibit low to moderate correlations and support the situational specificity hypothesis, suggesting that multiple raters should be consulted when assessing adult ADHD. Implications of these findings and recommendations for the continued study of SCT are discussed.

Longitudinal stability in reading comprehension is largely heritable from grades 1 to 6

Reading comprehension is a foundational academic skill and significant attention has focused on reading development. This report is the first to examine the stability and change in genetic and environmental influences on reading comprehension across Grades 1 to 6. This developmental range is particularly important because it encompasses the timespan in which most children move from learning how to read to using reading for learning. Longitudinal simplex models were fitted separately for two independent twin samples (N = 706; N = 976). Results suggested that the shared environment contributed to variance in early but not later reading. Instead, stability in reading development was largely mediated by continuous genetic influences. Thus, although reading is clearly a learned skill and the environment remains important for reading development, individual differences in reading comprehension appear to be also influenced by a core of genetic stability that persists through the developmental course of reading.

Mathematics achievement and anxiety and their relation to internalizing and externalizing behaviors

Although behavioral difficulties are well documented in reading disabilities, little is known about the relationship between math ability and internalizing and externalizing behaviors. Here, we use standardized measures to investigate the relation among early math ability, math anxiety, and internalizing and externalizing behaviors in a group of 366 second and third graders. Math achievement was significantly correlated with attentional difficulties and social problems but not with internalizing symptoms. The relation between math achievement and externalizing behavioral problems was stronger in girls than in boys. Math achievement was not correlated with trait anxiety but was negatively correlated with math anxiety. Critically, math anxiety differed significantly between children classified as math learning disabled (MLD), low achieving (LA), and typically developing (TD), with math anxiety significantly higher in the MLD and LA groups compared to the TD group. Our findings suggest that, even in nonclinical samples, math difficulties at the earliest stages of formal math learning are associated with attentional difficulties and domain-specific anxiety. These findings underscore the need for further examination of the shared cognitive, neural, and genetic influences underlying problem solving and nonverbal learning difficulties and accompanying internalizing and externalizing behaviors.