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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Attention-deficit/hyperactivity disorder (ADHD) and childhood-onset psychosis (COP) are chronic, heterogeneous disorders with symptoms that frequently co-occur, but the etiology of their comorbidity is unknown. Studies of each disorder indicate that both ADHD and COP are associated with a range of neuropsychological weaknesses, but few neuropsychological studies have directly compared groups with ADHD and COP. Methods: Groups with ADHD only (32 F, 48 M), COP only (5 F, 5 M), ADHD + COP (9 F, 21 M), and a control group with neither disorder (25 F, 44 M) completed a neuropsychological battery that included measures of verbal working memory, response inhibition, response speed and variability, and selective attention. Results: All three clinical groups exhibited significantly lower performance versus the control group on all neuropsychological measures, whereas the only significant difference between the clinical groups was a significantly larger weakness in verbal working memory in the groups with COP. Conclusions: The frequent co-occurrence between COP and ADHD may reflect shared neuropsychological weaknesses that are most pronounced on measures of working memory and response variability. [ABSTRACT FROM AUTHOR]

Background Attention-deficit/hyperactivity disorder ( ADHD) symptoms and mathematics ability are associated, but little is known about the genetic and environmental influences underlying this association. Methods Data came from more than 6,000 twelve-year-old twin pairs from the UK population-representative Twins Early Development Study. Parents rated each twin's behaviour using a DSM- IV-based 18-item questionnaire of inattentive and hyperactive-impulsive ADHD symptoms. Mathematics tests based on the UK National Curriculum were completed by each twin. The twins also completed standardised tests of reading and general cognitive ability. Multivariate twin model fitting was applied. Results Inattentive and hyperactive-impulsive ADHD symptoms were highly heritable (67% and 73% respectively). Mathematics ability was moderately heritable (46%). Mathematics ability and inattentiveness showed a significantly greater phenotypic correlation ( rp = −.26) and genetic correlation ( rA = −.41) than mathematics ability and hyperactivity-impulsivity ( rp = −.18; rA = −.22). The genetic correlation between inattentiveness and mathematics ability was largely independent from hyperactivity-impulsivity, and was only partially accounted for by genetic influences related to reading and general cognitive ability. Conclusions Results revealed the novel finding that mathematics ability shows significantly stronger phenotypic and genetic associations with inattentiveness than with hyperactivity-impulsivity. Genetic associations between inattentiveness and mathematics ability could only partially be accounted for by hyperactivity-impulsivity, reading and general cognitive ability. Results suggest that mathematics ability is associated with ADHD symptoms largely because it shares genetic risk factors with inattentiveness, and provide further evidence for considering inattentiveness and hyperactivity-impulsivity separately. DNA markers for ADHD symptoms (especially inattentiveness) may also be candidate risk factors for mathematics ability and vice versa. [ABSTRACT FROM AUTHOR]

Background: Reading disability (RD) and attention deficit/hyperactivity disorder (ADHD) are comorbid and genetically correlated, especially the inattentive dimension of ADHD (ADHD-I). However, previous research indicates that RD and ADHD enter into opposite gene by environment (G × E) interactions. Methods: This study used behavioral genetic methods to replicate these opposite G × E interactions in a sample of same-sex monozygotic and dizygotic twin pairs from the Colorado Learning Disabilities Research Center (CLDRC; ) and to test a genetic hypothesis for why these opposite interactions occur. Results: We replicated opposite G × E interactions for RD (bioecological) and ADHD-I (diathesis-stress) with parental education in the same sample of participants. The genetic hypothesis for this opposite pattern of interactions is that only genes specific to each disorder enter into these opposite interactions, not the shared genes underlying their comorbidity. To test this hypothesis, we used single models with an exploratory three-way interaction, in which the G × E interactions for each disorder were moderated by comorbidity. Neither three-way interaction was significant. The heritability of RD did not vary as a function of parental education and ADHD-I. Similarly, the heritability of ADHD-I did not vary as a function of parental education and RD. Conclusions: We documented opposite G × E interactions in RD and ADHD-I in the same overall twin sample, but the explanation for this apparent paradox remains unclear. Examining specific genes and more specific environmental factors may help resolve the paradox. [ABSTRACT FROM AUTHOR]

This study tests a multiple cognitive deficit model of reading disability (RD), attention-deficit/hyperactivity disorder (ADHD), and their comorbidity. A structural equation model (SEM) of multiple cognitive risk factors and symptom outcome variables was constructed. The model included phonological awareness as a unique predictor of RD and response inhibition as a unique predictor of ADHD. Processing speed, naming speed, and verbal working memory were modeled as potential shared cognitive deficits. Model fit indices from the SEM indicated satisfactory fit. Closer inspection of the path weights revealed that processing speed was the only cognitive variable with significant unique relationships to RD and ADHD dimensions, particularly inattention. Moreover, the significant correlation between reading and inattention was reduced to non-significance when processing speed was included in the model, suggesting that processing speed primarily accounted for the phenotypic correlation (or comorbidity) between reading and inattention. This study illustrates the power of a multiple deficit approach to complex developmental disorders and psychopathologies, particularly for exploring comorbidities. The theoretical role of processing speed in the developmental pathways of RD and ADHD and directions for future research are discussed. [ABSTRACT FROM AUTHOR]

Background: It has been proposed that some of the variability in reporting of associations between attention deficit hyperactivity disorder (ADHD) and candidate genes may result from mixing of genetically heterogeneous forms of ADHD using DSM-IV criteria. The goal of the current study is to test whether population-based ADHD subtypes defined by latent class analysis help resolve issues of variable findings across individual gene association studies. Methods: Three studies which had previously reported no associations between polymorphisms of the DRD4 and DAT genes and DSM-IV defined ADHD were reanalyzed using population-based and DSM-IV defined ADHD subtypes. Results: Across studies no significant associations were found for either DRD4 or DAT polymorphisms using DSM-IV ADHD subtypes. In contrast, a significant association was found between the combined data set for the 440 base pair 3′ DAT VNTR polymorphism and population-defined severe combined ADHD (OR = 1.25, p = .01). A marginally significant association was also found between the 7 repeat DRD4 allele and population-defined severe combined ADHD. Conclusion: Use of alternative population-based defined ADHD subtypes may help resolve some of the variable results presented for candidate gene association studies in ADHD. [ABSTRACT FROM AUTHOR]

Behavioral genetic studies provide strong evidence that attention-deficit/hyperactivity disorder (ADHD) has a substantial genetic component. Yet, due to the complexity of the ADHD phenotype, questions remain as to the specific genes that contribute to this condition as well as the pathways from genes to behavior. Endophenotypes, or phenotypes that are more closely linked to the neurobiological substrate of a disorder, offer the potential to address these two issues simultaneously (Freedman, Adler, & Leonard, 1999). Thus far, potential endophenotypes for ADHD have not been systematically studied. The current paper reviews evidence supporting the use of deficits on neurocognitive measures of executive functions for this purpose. Such deficits are a correlate of ADHD and show preliminary evidence of heritability and association with relevant candidate genes. Nonetheless, studies that have assessed the familial and genetic overlap of neurocognitive impairments with ADHD have yielded inconsistent results. In order for executive function deficits to be used as an endophenotype for ADHD, we recommend greater attention to the neurocognitive heterogeneity of this disorder and to the precision of measurement of the neuropsychological tests employed. We also discuss empirical strategies that may be necessary to allow such research to progress prior to full resolution of the pathophysiological basis of ADHD. [ABSTRACT FROM AUTHOR]

This study investigated the association between reading disability (RD) and internalizing and externalizing psychopathology in a large community sample of twins with ( NO= 209) and without RD ( NO= 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, and to test if common familial influences contributed to the association between RD and other disorders. Results indicated that individuals with RD exhibited significantly higher rates of all internalizing and externalizing disorders than individuals without RD. However, logistic regression analyses indicated that RD was not significantly associated with symptoms of aggression, delinquency, oppositional defiant disorder, or conduct disorder after controlling for the significant relation between RD and ADHD. In contrast, relations between RD and symptoms of anxiety and depression remained significant even after controlling for comorbid ADHD, suggesting that internalizing difficulties may be specifically associated with RD. Analyses of gender differences indicated that the significant relation between RD and internalizing symptoms was largely restricted to girls, whereas the association between RD and externalizing psychopathology was stronger for boys. Finally, preliminary etiological analyses suggested that common familial factors predispose both probands with RD and their non-RD siblings to exhibit externalizing behaviors, whereas elevations of internalizing symptomatology are restricted to individuals with RD. [ABSTRACT FROM AUTHOR]