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.

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.

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.

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.

Regional cerebellar volume and cognitive function from adolescence to late middle age.

Cerebellar morphology and function have been implicated in a variety of developmental disorders, and in healthy aging. Although recent work has sought to characterize the relationships between volume and age in this structure during adolescence, young, and older adulthood, there have been no investigations of regional cerebellar volume from adolescence through late middle age. Middle age in particular has been largely understudied, and investigating this period of the lifespan may be especially important for our understanding of senescence. Understanding regional patterns of cerebellar volume with respect to age during this portion of the lifespan may provide important insight into healthy aging and cognitive function as well as pathology from adolescence into later life. We investigated regional cerebellar volume using a highly novel lobular segmentation approach in conjunction with a battery of cognitive tasks in a cross-sectional sample of 123 individuals from 12 to 65 years old. Our results indicated that regional cerebellar volumes show different patterns with respect to age. In particular, the more posterior aspect of the neocerebellum follows a quadratic "inverse-U" pattern while the vermis and anterior cerebellum follow logarithmic patterns. In addition, we quantified the relationships between age and a variety of cognitive assessments and found relationships between regional cerebellar volumes and performance. Finally, exploratory analyses of sex differences in the relationships between regional cerebellar volume, age, and cognition were investigated. Taken together, these results provide key insights into the development and aging of the human cerebellum, and its role in cognitive function across the lifespan.

Cognitive disengagement syndrome in pediatric spina bifida.

The primary aim of this study was to characterize Cognitive Disengagement Syndrome (CDS) symptomatology in youth with spina bifida (SB). One hundred and sixty-nine patients aged 5-19 years old were drawn from clinical cases seen through a multidisciplinary outpatient SB clinic at a children's hospital between 2017 and 2019. Parent-reported CDS and inattention were measured using Penny's Sluggish Cognitive Tempo Scale and the Vanderbilt ADHD Rating Scale. Self-reported internalizing symptoms were measured with the 25-item Revised Children's Anxiety and Depression Scale (RCADS-25). We replicated Penny's proposed 3-factor structure of CDS with slow, sleepy, and daydreamer components. The slow component of CDS overlapped heavily with inattention, while the sleepy and daydreamer components were distinct from inattention and internalizing symptoms. Eighteen percent (22 of 122) of the full sample met criteria for elevated CDS, and 39% (9 of 22) of those patients did not meet criteria for elevated inattention. Diagnosis of myelomeningocele and presence of a shunt were associated with greater CDS symptoms. CDS can be measured reliably in youth with SB and can be discriminated from inattention and internalizing symptoms in this population. ADHD rating scale measures fail to identify a substantial portion of the SB population with attention-related challenges. Standard screening for CDS symptoms in SB clinics may be important to help identify clinically impairing symptoms and design targeted treatment plans.

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.

Resting-state connectivity underlying cognitive control's association with perspective taking in callous-unemotional traits.

Callous-Unemotional (CU) traits are often associated with impairments in perspective taking and cognitive control (regulating goal directed behavior); and adolescents with CU traits demonstrate aberrant brain activation/connectivity in areas underlying these processes. Together cognitive control and perspective taking are thought to link mechanistically to explain CU traits. Because increased cognitive control demands modulate perspective taking ability among both typically developing samples and individuals with elevated CU traits, understanding the neurophysiological substrates of these constructs could inform efforts to alleviate societal costs of antisocial behavior. The present study uses GIMME to examine the heterogenous functional brain properties (i.e., connection density, node centrality) underlying cognitive control's influence on perspective taking among adolescents on a CU trait continuum. Results reveal that cognitive control had a negative indirect association with CU traits via perspective taking; and brain connectivity indirectly associated with lower CU traits - specifically the social network via perspective taking and conflict network via cognitive control. Additionally, less negative connection density between the social and conflict networks was directly associated with higher CU traits. Our results support the growing literature on cognitive control's influence on socio-cognitive functioning in CU traits and extends that work by identifying underlying functional brain properties.

Efficiency of Heterogenous Functional Connectomes Explains Variance in Callous-Unemotional Traits After Computational Lesioning of Cortical Midline and Salience Regions.

Introduction: Callous-unemotional (CU) traits are a youth antisocial phenotype hypothesized to be a result of differences in the integration of multiple brain systems. However, mechanistic insights into these brain systems are a continued challenge. Where prior work describes activation and connectivity, new mechanistic insights into the brain's functional connectome can be derived by removing nodes and quantifying changes in network properties (hereafter referred to as computational lesioning) to characterize connectome resilience and vulnerability. Methods: Here, we study the resilience of connectome integration in CU traits by estimating changes in efficiency after computationally lesioning individual-level connectomes. From resting-state data of 86 participants (48% female, age 14.52 ± 1.31) drawn from the Nathan Kline institute's Rockland study, individual-level connectomes were estimated using graphical lasso. Computational lesioning was conducted both sequentially and by targeting global and local hubs. Elastic net regression was applied to determine how these changes explained variance in CU traits. Follow-up analyses characterized modeled node hubs, examined moderation, determined impact of targeting, and decoded the brain mask by comparing regions to meta-analytic maps. Results: Elastic net regression revealed that computational lesioning of 23 nodes, network modularity, and Tanner stage explained variance in CU traits. Hub assignment of selected hubs differed at higher CU traits. No evidence for moderation between simulated lesioning and CU traits was found. Targeting global hubs increased efficiency and targeting local hubs had no effect at higher CU traits. Identified brain mask meta-analytically associated with more emotion and cognitive terms. Although reliable patterns were found across participants, adolescent brains were heterogeneous even for those with a similar CU traits score. Conclusion: Adolescent brain response to simulated lesioning revealed a pattern of connectome resiliency and vulnerability that explains variance in CU traits, which can aid prediction of youth at greater risk for higher CU traits.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The internal and external validity of sluggish cognitive tempo and its relation with DSM-IV ADHD.

Studies of subtypes of DSM-IV attention-deficit/hyperactivity disorder (ADHD) have provided inconsistent support for the discriminant validity of the combined type (ADHD-C) and predominantly inattentive type (ADHD-I). A large sample of children and adolescents with ADHD (N = 410) and a comparison group without ADHD (N = 311) were used to test the internal and external validity of sluggish cognitive tempo (SCT), a dimension characterized by low energy and sleepy and sluggish behavior. SCT scores were then incorporated in analyses of ADHD subtypes to test whether the discriminant validity of ADHD-C and ADHD-I could be improved by including SCT symptoms as part of the criteria for ADHD-I. Factor analyses of parent and teacher ratings indicated that six SCT items loaded on a factor separate from symptoms of ADHD and other psychopathology, providing important support for the internal validity of SCT. The external validity of SCT was supported by significant associations between SCT and measures of functional impairment and neuropsychological functioning when symptoms of ADHD and other psychopathology were controlled. However, contrary to initial predictions, high levels of SCT did not identify a subgroup of ADHD-I that was clearly distinct from ADHD-C. Instead, the current results suggest that DSM-IV inattention and SCT are separate but correlated symptom dimensions that are each independently associated with important aspects of functional impairment and neuropsychological functioning.