Cognitive functioning in children with and without Attention-deficit/Hyperactivity Disorder with and without comorbid learning disabilities

This study attempted to determine whether children with the combined subtype of attention-deficit/hyperactivity disorder (ADHD) have impairments in cognitive functioning and motor skills. The specific effect of the comorbidity of learning disabilities (LD) was also investigated. A battery of cognitive tests was administered to 26 children with a clinical diagnosis of ADHD-combined subtype (ADHD/C), to 24 children with ADHD/C with a comorbid diagnosis of LD (ADHD/C+LD), and to 102 participants without disabilities, all between ages 7 and 10. The testing battery consisted of tasks assessing memory, visuospatial and verbal abilities, and fine motor skills. In general, the test results of children with ADHD/C were poorer than those of the control group but better than the results of children with a combined ADHD/C+LD diagnosis (with the exception of motor skills). The predictive accuracy of the testing battery tasks in children with ADHD/C and ADHD/C+LD was examined. The results of a standard procedure of discriminant function analyses revealed that the measures correctly classified 73.6% of the children.     

Written expression performance in adolescents with attention-deficit/hyperactivity disorder (ADHD)

We examined written expression performance in a sample of adolescents with ADHD and subthreshold ADHD using two different strategies: examining performance on standardized measures of written expression and using other indicators of written expression developed in this study. We examined associations between standardized measures of written expression, cognitive processing measures (working memory, processing speed, language, fine motor ability, and reading efficiency) and behavioral ratings of ADHD by parents and teachers. We also developed a coding scheme for a writing sample to measure productivity and the ratio of self-corrections to errors. The results indicated that written expression performance was most consistently associated with cognitive processing measures and not behavioral ratings of ADHD, based on correlational and simultaneous regression analyses. These results were consistent in the analyses with both the standardized measures and the coding scheme measures of written expression. Findings generally remained robust, regardless of whether participants who met criteria for a learning disability were included or excluded in the analyses. The current results suggest that written expression difficulties in adolescents with ADHD are attributable to processing difficulties that may be associated with ADHD, not to ADHD reported symptoms. Implications for assessment and intervention are discussed.     

ADHD and dyscalculia: Evidence for independent familial transmission

The familial relationship between dyscalculia and attention-deficit/hyperactivity disorder (ADHD) was assessed. We conducted a familial risk analysis using probands with and without ADHD of both genders and their first-degree relatives. Participants were assessed with structured diagnostic interviews and a cognitive test battery. We found elevated rates of ADHD in relatives of both ADHD proband groups, regardless of dyscalculia status, and elevated rates of dyscalculia in relatives of probands with dyscalculia, irrespective of ADHD status. There was no evidence for cosegregation or assortative mating. Our findings support the hypothesis that ADHD and dyscalculia are independently transmitted in families and are etiologically distinct. These results reinforce the current nosological approach to these disorders and underscore the need for separate identification and treatment strategies for children with both conditions.     

ADHD and reading disability in male adults: is there a connection?

The present study examined the comorbidity between attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) in male adults. Participants were 120 men, of whom 24 were classified as having ADHD. The basis for the diagnosis was two self-report scales validated by interviews and background data. An extensive battery was used to assess phonological abilities and various aspects of reading skills. No differences were obtained between adults with and without ADHD on measures of either phonological processing skills or word decoding, indicating a low comorbidity with RD. This finding was valid even when different criteria were used to diagnose RD. However, the two groups differed in reading comprehension, with individuals with ADHD performing poorly in tests of reading comprehension. These results are compatible with the view that reading comprehension involves many of the higher cognitive control functions assumed to be impaired in ADHD. However, these attentional control functions are not critical to word recognition, which is determined by a more encapsulated phonological processing module. The pattern of associations between ADHD and RD observed in the present study is explained with reference to the differential attentional demands of the two aspects of reading.     

Genome‐Wide Association Study of Latent Cognitive Measures in Adolescence: Genetic Overlap With Intelligence and Education

Individual differences in executive functions (EF) are heritable and predictive of academic attainment (AA). However, little is known about genetic contributions to EFs or their genetic relationship with AA and intelligence. We conducted genome‐wide association analyses for processing speed (PS) and the latent EF measures of working memory (WM) and inhibitory control (IC) in 4,611 adolescents from the Avon Longitudinal Study of Parents and Children. While no loci reached genome‐wide significance, common genetic variants explained 30% of the variance in WM and 19% in PS. In contrast, we failed to find common genetic contributions to IC. Finally, we examined shared genetic effects between EFs and general intelligence, AA and ADHD. We identified significant genetic correlations between WM, intelligence, and AA. A more specific pattern was observed for PS, with modest genetic overlap with intelligence. Together these findings highlight diversity in the genetic contributions to specific cognitive functions and their genetic relationship with educational and psychiatric outcomes.     

Effectiveness of a school-based multicomponent program for the treatment of children with ADHD

The objective of this study was to evaluate the efficacy of a multicomponent program for treating attention-deficit/hyperactivity disorder (ADHD) carried out by teachers in a classroom context. Dependent measures included neuropsychological tasks, behavioral rating scales for parents and teachers, direct observation of behavior in the classroom, and academic records of children with ADHD. Fifty children with ADHD participated in the study. The teachers of 29 of the 50 students were trained in the use of behavior modification techniques, cognitive behavior strategies, and instructional management strategies. The other 21 students formed the control group. Parents' and teachers'ratings detected improvements in primary symptoms (inattention-disorganization, hyperactivity-impulsivity) and in behavioral difficulties usually associated with ADHD (e.g., antisocial behavior, psychopathological disorders, anxiety). Furthermore, the results showed increased academic scores, enhanced classroom behavioral observations, and improved teachers' knowledge about the strategies directed toward responding to the children's educational needs.     

Clinical appraisal of spelling ability and its relationship to phonemic awareness (blending,segmenting, elision,and reversal), phonological memory,and reading in reading disabled,ADHD, and normal children

Seventy-eight 8-to-12-year-old children (34 ReadingDisabled; 31 Attention-Deficit-Hyperactivity-Disordered; and 13diagnosed normal controls) were given a battery oftests including cognitive, linguistic, academic,phonemic awareness, and memory tests. As part of theacademic battery an 8-point spelling rating scale wasdeveloped (Rating Scale) that resulted in threedifferent scores which reliably discriminated amongthe three groups. Relationships between phonemicawareness, phonological memory, reading and spellingwere explored. Zero-order and second-ordercorrelations were completed with indications thatphonemic awareness tasks (elision, blending, reversal,and segmenting) and phonological memory (WISC-IIIDigit Span) are significantly correlated with readingdecoding and spelling measures with slightly highercorrelations with the Rating Scale. Regressionanalyses resulted in a large proportion of thevariance on reading and spelling tasks accounted forby phonemic awareness (particularly elision andreversal) and phonological memory. The ReadingDisabled group was found to produce more errors thatwere phonetically inaccurate than the other twogroups. The demand of spelling ten ``error' wordsbeyond the RD students' achievement level appeared toelicit greater weaknesses in their phonologicalrecoding abilities than in those of the ADHD ornormally achieving students.     

Early Histories of School‐Aged Children With Attention‐Deficit/ Hyperactivity Disorder

In a prospective study of developmental outcomes in relation to early‐life otitis media, behavioral, cognitive, and language measures were administered to a large, diverse sample of children at 2, 3, 4, 6, and 9–11 years of age (N = 741). At 9–11 years of age, 9% of the children were categorized as having attention‐deficit/hyperactivity disorder (ADHD) based on parent report. Compared to the non‐ADHD group, the ADHD group had higher (i.e., less favorable) scores on parent and teacher versions of the Child Behavior Checklist at all ages. Children in the ADHD group also had lower scores on cognitive and receptive language measures in preschool. The findings support the concept that ADHD is a cognitive as well as a behavioral disorder.     

Handwriting fluency and visuospatial generativity at primary school

Handwriting is a complex activity that involves continuous interaction between lowerlevel perceptual-motor and higher-level cognitive processes. All handwriting models describe involvement of executive functions (EF) in handwriting development. Particular EF domains associated with handwriting include maintenance of information in working memory, inhibition of prepotent responses, and shifting and sustaining of attention. Generativity, an EF domain that has not been extensively studied, may play a role in the acquisition and automation of handwriting. We hypothesized that neuropsychological performances and handwriting fluency would be mutually associated, and that visuospatial generativity could have a specific role in handwriting speed. We enrolled 96 children who completed a comprehensive neuropsychological battery. The study found that handwriting speed was associated with visuospatial fluency, which involves behavioural execution and initiation. In learning and performing handwriting, there is an inherent non-exclusive role of fine motor skills.     

Preschool twin study of the relation between attention-deficit/hyperactivity disorder and prereading skills

Numerous studies have examined the etiology of the association between reading difficulties and attention-deficit hyperactivity disorder (ADHD) in school-age children, but little is known about the relation between prereading skills and ADHD behaviors prior to the beginning of formal reading instruction. A population-based sample of 809 pairs of preschool twins completed an extensive battery of prereading measures, and the parent of each twin completed an ADHD rating scale. Phenotypic analyses revealed small but significant correlations between DSM-IV inattention ratings and six prereading composite measures, whereas hyperactivity–impulsivity symptoms were not independently associated with any of the prereading scores. Multivariate twin analyses indicated that virtually all of the phenotypic correlation between inattention and prereading performance is attributable to common genetic influences, consistent with results obtained in studies of older twins. Although additional research is needed to test alternative causal models in children younger than five years old, these results are most consistent with the hypothesis that reading difficulties and inattention symptoms are attributable to common genetic influences.     

The influence of feedback of diagnosis and executive function skills on rates of false positive and false negative outcomes for ADHD

This study examined executive function (EF) skills and self-reported symptoms of ADHD. EF skills were measured to determine whether skills were different between groups that reported clinical levels of ADHD symptoms (clinical group) and nonclinical levels of ADHD symptoms (nonclinical group). EF skills in the nonclinical group were also investigated to determine whether differences existed for those who received false positive and negative feedback about an ADHD diagnosis. Results indicated statistically and clinically significant differences in EF skills between the clinical and nonclinical group. Participants in the nonclinical group who reported elevated scores on the ADHD screener after receiving false positive feedback had statistically significantly different EF function scores, but not clinically significant scores, compared to the participants in nonclinical group who received negative feedback.     

Theoretical and methodological implications of associations between executive function and mathematics in early childhood

Despite agreement about the importance of executive function (EF) for children’s early math achievement, its treatment in correlational studies reflects a lack of agreement about the theoretical connection between the two. It remains unclear whether the association between EF and math operates through a latent EF construct or specific EF components. Specifying the correct measurement model has important theoretical implications for the predicted effects of EF interventions on children’s math achievement. In the current study, we tested whether associations between EF and math operate via a latent EF factor, or via specific EF components using data from a large, nationally representative sample. We then replicated these same analyses with a meta-analytic database drawn from ten studies that collected measures of children’s EF and math achievement. Our results lend support to explanations that a single EF factor accounts for most of the EF component-specific associations with math achievement. We discuss theoretical and methodological implications of these findings for future work.     

Neuropsychology of Early-treated Phenylketonuria: Specific Executive Function Deficits

This study explored the hypothesis that children with early-treated phenylketonuria (PKU) are selectively impaired on executive function measures, even when still on diet. The rationale for this hypothesis is that even mild elevations in phenylalanine (Phe) can lead to lower central levels of biogenic amines, including dopamine (DA). We hypothesize that this mild DA depletion causes subtle prefrontal dysfunction, which in turn affects executive functions such as set maintenance, planning, and organized search. 11 preschool early-treated PKU children (M age = 4.64) and a sample of age- and IQ-matched unaffected peers (n = 11) were evaluated on a battery of executive function (EF) measures. In addition, a "non-executive function" task, recognition memory, was administered to all subjects. Group comparisons demonstrated that PKU children were significantly impaired on an executive function composite score; there were no group differences, however, in recognition memory. These results supported the hypothesized specific deficit in executive function. Furthermore, within the PKU group the executive function composite score was significantly negatively correlated with concurrent phenylalanine levels, even after controlling for the correlation between IQ and executive function skills. This second finding provides support for the proposed biochemical mechanism underlying the specific cognitive deficits.     

Intact and Impaired Memory Functions in Autism

This study examined memory functions in individuals with autism. Based on previous evidence of executive function (EF) deficits, we hypothesized that subjects with autism would demonstrate a pattern of intact and imparred memory functions similar to that found in other groups with EF deficits, such as patients with frontal lobe pathology. We compared the performance of high-functioning children and adolescents with autism (n = 19) and clinical comparison subjects (n = 19) matched on sex, CA, and VIQ on measures of memory and EF. The group with autism performed significantly worse than comparison subjects on measures of temporal order memory, source memory, supraspan free recall, working memory, and EF, but not on short- and long-term recognition, cued recall, or new learning ability, consistent with the predictions of the EF theory. The cognitive measures were significantly more intercorrelated in the autism group than the comparison group, consistent with a limit in central cognition.     

Identifying Attention Deficit Hyperactive Disorder with the WISC-R and the Stroop Color and Word Test

Twenty-nine children with a diagnosis of Attention Deficit Hyperactive Disorder (ADHD) were compared to a group of 21 emotionally disturbed (ED) children and a control group (CO) of 20 nonproblem children. The meaures used in the comparison were the 12 subtests of the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the Stroop Color and Word Test (SCWT). The results showed that the CO group was superior to the ADHD and ED groups and that the ED group performed better than the ADHD group on most of the variables. A stepwise discriminant function analysis showed that similar WISC-R subtests differentiated between the ADHD group and the ED and CO groups. Two measures of the SCWT helped in discriminating between the ADHD and ED groups, but not between the ADHD and CO groups. The authors discuss the meaning of these findings and their contribution to better understanding of the ADHD group, its specific cognitive processing, and its problems.     

Cognitive profiling in Chinese developmental dyslexia with attention-deficit/hyperactivity disorders

The cognitive profiles of children with Developmental Reading Disorder (RD) and Attention-Deficit/Hyperactivity Disorders (ADHD) have been extensively studied in alphabetic language communities. Deficits in phonological processing and rapid naming have been implicated as core features of RD although whether the latter is a deficit specific to RD remains controversial. Similar research aiming to explore the cognitive profiles of children with both RD and ADHD in non-alphabetic language communities is limited. The specificity of rapid naming deficit to RD among Chinese has yet to be studied. In the first study, 43 Chinese children with confirmed diagnoses of RD + ADHD were assessed on their cognitive abilities in relating to reading. In the second study, the specificity deficit hypothesis of rapid naming to RD but not ADHD was examined. A digit naming test was administered to the RD + ADHD group (43 subjects) and an ADHD only group (49 subjects). In regard to cognitive profiling, rapid naming and orthographic knowledge were found to be the most common deficits among the Chinese RD + ADHD group. This co-morbid group was also found to have a significant deficit performance on the rapid naming task than the ADHD only group. The present findings support the double dissociation hypothesis in cognitive deficit between RD and ADHD. The results of both studies are discussed with reference to the findings of the Western counterparts.     

Cognitive Stimulation as a Mechanism Linking Socioeconomic Status With Executive Function: A Longitudinal Investigation

Executive functions (EF), including working memory, inhibition, and cognitive flexibility, vary as a function of socioeconomic status (SES), with children from economically disadvantaged backgrounds having poorer performance than their higher SES peers. Using observational methods, we investigated cognitive stimulation in the home as a mechanism linking SES with EF. In a sample of 101 children aged 60–75 months, cognitive stimulation fully mediated SES-related differences in EF. Critically, cognitive stimulation was positively associated with the development of inhibition and cognitive flexibility across an 18-month follow-up period. Furthermore, EF at T1 explained SES-related differences in academic achievement at T2. Early cognitive stimulation—a modifiable factor—may be a desirable target for interventions designed to ameliorate SES-related differences in cognitive development and academic achievement.     

Understanding the relations between RAN letter subtest components and word reading in first-grade students

First-grade students (N = 221) were individually tested on a battery of cognitive and achievement measures of verbal fluency, visual attention, phonological awareness, orthographic recognition, rapid automatized naming (RAN) of letters and objects, and reading. All tests were subjected to postacquisition scoring, and all RAN measures were segregated into measures of articulation time, pause time, and consistency of the pause time. Structural equation modeling demonstrated that word reading was directly and significantly predicted by RAN letter naming and general RAN cognitive processing time of objects. Moreover, RAN letter reading constructs were significantly and directly predicted by the latent variables of phonological awareness, orthographic recognition, and general RAN object articulation and cognitive processing times. RAN letter naming constructs were also significantly and indirectly predicted by visual attention. The reading model was found to be consistent with a total mediation of the relation of phonological awareness and reading through RAN letter naming and supported the validity of the RAN letter naming subtest as a basic letter reading test. These findings supported the double-deficit hypothesis for letter reading. We suggest that phonological memory is a basic factor underlying general RAN cognitive processing time of objects and domain-specific information associated with phonemes and their graphic representations.     

Boys with reading disabilities and/or ADHD: distinctions in early childhood

We examined distinctions in the early childhood characteristics of boys with reading disabilities (RD) and/or attention-deficit/ hyperactivity disorder (ADHD). A four-group mixed design consisting of boys identified at age 11 with reading disabilities only (RD only; n = 46), reading disabilities and ADHD (RD/ADHD; n = 16), ADHD only (n = 20), and a comparison group (n = 281) was utilized. Differences on receptive and expressive language and temperament for ages 3 and 5 were investigated. Analyses indicated that the boys from the RD-only group performed worse on measures of receptive and expressive language. The results also indicated that boys from the RD/ADHD groups consistently performed worse on measures of receptive language and exhibited more behaviors indicative of an undercontrolled temperament. In summary, we suggest that reading disabilities and ADHD represent moderately unique disorders that frequently co-occur and are characterized by distinct developmental pathways.     

Group-based intervention on attention and executive functions in the school context

The objective of the study was to examine the effects of a group-based behavioural, cognitive and skills training intervention (Maltti) provided in schools for elementary school pupils with attention and executive function (EF) deficits. The treatment effects were identified by comparing an intervention group (n = 46) with a waitlist control group (n = 26). Specific effects of the intervention on behavioural deficits in attention and EF in a classroom setting as well as on academic skills were examined. Our analysis indicated that significant intervention effects could be found in the behavioural manifestation of attentional and executive skills in the classroom setting among children (n = 30) who were evaluated as having moderate symptoms in the pre-intervention assessment. Positive effects of the intervention were also observed in arithmetic and reading skills. The severity level of pre-intervention attention and EF deficits did not moderate the results observed in the academic skills tests. The results of this study suggest that a combination of behavioural, cognitive and skills training methods applied in a school context can be effective in reducing attention and EF problems and enhancing the academic performance of children with attention and EF deficits.