Fine motor skills in South African children with symptoms of ADHD: influence of subtype, gender, age, and hand dominance

A Critical View on Motor-based Interventions to Improve Motor Skill Performance in Children With ADHD: A Systematic Review and Meta-analysis

OBJECTIVE

To map the effect of motor-based interventions on motor skills in children with ADHD.

METHOD

A systematic literature search was performed in Pubmed, Web of Science, and the SCOPUS database (last search: October 30th 2022). Methodological quality was assessed using the PEDro-scale and the quality of evidence was determined with the GRADE-method. Meta-analysis was performed when at least five studies were available.

RESULTS

Thirteen studies (7 RCTs) satisfied the inclusion criteria, five of which were eligible for meta-analysis. Only one of the included studies reached the low risk of bias threshold. Comparing different motor-based interventions to any non-motor control intervention showed large motor skill improvements (SMD = 1.46; 95% CI = [1.00;1.93]; I² = 47.07%). The most effective type of motor-based intervention and the optimal treatment parameters could not be determined yet.

CONCLUSION

Motor-based interventions in general seem to improve motor skills in children with ADHD. Additional RCTs are needed to increase current low GRADE confidence.

Investigating Motor Preparation in Autism Spectrum Disorder With and Without Attention Deficit/Hyperactivity Disorder

This study investigated motor preparation and action-consequence prediction using the lateralized readiness potential (LRP). Motor impairments are common in autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), which commonly co-occur. Alterations in predictive processes may impact motor planning. Whether motor planning deficits are characteristic of ASD broadly or magnified in the context of co-morbid ADHD is unclear. ASD children with (ASD + ADHD; n = 12) and without (ASD - ADHD; n = 9) comorbid ADHD and typical controls (n = 29) performed voluntary motor actions that either did or did not result in auditory consequences. ASD - ADHD children demonstrated LRP enhancement when their action produced an effect while ASD + ADHD children had attenuated responses regardless of action-effect pairings. Findings suggest influence of ADHD comorbidity on motor preparation and prediction in ASD.

How effective is fine motor training in children with ADHD? A scoping review

Background

Motor deficiencies are observed in a large number of children with ADHD. Especially fine motor impairments can lead to academic underachievement, low self-esteem and frustration in affected children. Despite these far-reaching consequences, fine motor deficiencies have remained widely undertreated in the ADHD population. The aim of this review was to systematically map the evidence on existing training programs for remediating fine motor impairments in children with ADHD and to assess their effectiveness.

Methods

The scoping review followed the PRISMA-ScR guidelines. In March 2020, PsycINFO, MEDLINE (PubMed), Web of Science, Google Scholar and The Cochrane Database of Systematic Reviews were searched for evidence. The eligibility criteria and the data charting process followed the PICO framework, complemented by study design. The investigated population included children with a formal ADHD diagnosis (either subtype) or elevated ADHD symptoms aged between 4 and 12 years, both on and off medication. All training interventions aiming at improving fine motor skills, having a fine motor component or fine motor improvements as a secondary outcome were assessed for eligibility; no comparators were specified.

Results

Twelve articles were included in the final report, comprising observational and experimental studies as well as a review. Both offline and online or virtual training interventions were reported, often accompanied by physical activity and supplemented by training sessions at home. The training programs varied in length and intensity, but generally comprised several weeks and single or multiple training sessions per week. All interventions including more than one session were effective in the treatment of fine motor deficiencies in children with ADHD and had a wide range of additional positive outcomes. The effects could be maintained at follow-up.

Conclusions

Fine motor training in children with ADHD can be very effective and multiple approaches including specific fine motor and cognitive training components, some kind of physical activity, feedback mechanisms, or multimodal treatments can be successful. Training programs need to be tailored to the specific characteristics of the ADHD population. A mHealth approach using serious games could be promising in this context due to its strong motivational components.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02916-5.

Cross-lateralisation in children with attention-deficit/hyperactivity disorder and motor skill performance

Cross‐lateralisation and increased motor difficulties have been reported in children with attention‐deficit/hyperactivity disorder (ADHD). Nevertheless, the question of how crossed (i.e. mixed preference) or uncrossed (i.e. same side preference) lateralisation impacts motor performance in children with ADHD has yet to be examined. In this study, previously validated observational measures of hand and foot preference were used to identify right‐handed children with ADHD who display cross‐ (n = 29) and uncross‐lateralisation (n = 31). An uncross‐lateralised typically developing (TD) group (n = 32) was also identified, and included as a control. Motor performance was assessed with seven valid and reliable fine and gross motor tasks performed with both preferred and non‐preferred limbs. Group, task and sex‐related effects were examined. Findings revealed that male (but not female) cross‐lateralised children with ADHD performed significantly worse, respectively, in two of the fine motor tasks (spiral tracing [p < .01], and dot filling [p < .05]). Results suggest that cross‐lateralised hand and foot preference may affect complex motor skills in male children with ADHD. Furthermore, characteristics of ADHD may manifest differently in male and female children. Findings highlight the importance of considering both hand and foot preference when targeting motor interventions for children with ADHD.

New Insights on the Effects of Methylphenidate in Attention Deficit Hyperactivity Disorder

This narrative review describes an overview of the multiple effects of methylphenidate (MPH) in attention-deficit/hyperactivity disorder (ADHD) and its potential neurobiological targets. It addressed the following aspects: 1) MPH effects on attention and executive functions in ADHD; 2) the relation between MPH efficacy and dopamine transporter gene (DAT) polymorphism; and 3) the role of MPH as an epigenetic modulator in ADHD. Literature analysis showed that MPH, the most commonly used psychostimulant in the therapy of ADHD, acts on multiple components of the disorder. Marked improvements in attentional and executive dysfunction have been observed in children with ADHD during treatment with MPH, as well as reductions in neurological soft signs. MPH efficacy may be influenced by polymorphisms in the DAT, and better responses to treatment were associated with the 10/10 genotype. Innovative lines of research have suggested that ADHD etiopathogenesis and its neuropsychological phenotypes also depend on the expression levels of human endogenous retrovirus (HERV). In particular, several studies have revealed that ADHD is associated with HERV-H over-expression and that MPH administration results in decreased expression levels of this retroviral family and a reduction in the main symptoms of the disorder. In conclusion, there is a confirmed role for MPH as an elective drug in the therapy of ADHD alone or in association with behavioral therapy. Its effectiveness can vary based on DAT polymorphisms and can act as a modulator of HERV-H gene expression, pointing to targets for a precision medicine approach.

Gender and hand dominance on fine motor skills among Grade 1–7 learners with attention-deficit hyperactivity disorder

Children diagnosed with attention-deficit/hyperactivity disorder encounter difficulties in many activities in their daily lives that require motor coordination skills. The aim of this study was to establish whether children with attention-deficit/hyperactivity disorder have deficits in fine motor skills. Eighty male and female learners diagnosed with attention-deficit/hyperactivity disorder matched with 80 non-attention-deficit/hyperactivity disorder from the North West and Limpopo provinces (South Africa), aged 7–13  years, participated in the study. All participants completed the grooved pegboard test, the maze coordination task, and the finger tapping test. These instruments measure various functions of motor speed and eye–hand coordination. The findings reveal that children with attention-deficit/hyperactivity disorder performed significantly poorer than the control group with regard to the grooved pegboard and maze coordination tasks, but not with the finger tapping task. There were no gender differences in all the tests. Performance on the maze coordination task with the non-dominant hand was poorer for the attention-deficit/hyperactivity disorder group with regard to the time taken to complete the task. However, no hand dominance differences were found on the grooved pegboard and finger tapping tests. The study revealed a relationship between attention-deficit/hyperactivity disorder symptomatology and motor problems with regard to complex tasks of accuracy, but not on a simple task of motor speed. It is, therefore, recommended that since children with attention-deficit/hyperactivity disorder show motor deficiencies, motor skill training should be considered as part of the intervention, as these skills are needed for many daily activities and academic competencies.

Exercise Interventions in Children and Adolescents With ADHD: A Systematic Review

OBJECTIVE

Exercise has attracted attention as a potential helpful intervention in children with ADHD. Effects are emphasized on cognition, social-emotional, and motor development.

METHOD

A systematic literature search was conducted using the electronic databases Web of Science, PubMed, Scopus, and ERIC to analyze the efficacy of different types of exercise interventions in children and adolescents with ADHD. Seven studies examining the acute and 14 studies examining the long-term effects were included.

RESULTS

The largest effects were reported for mixed exercise programs on ADHD symptomatology and fine motor precision. However, because of the large differences in the study designs, the comparability is limited.

CONCLUSION

At this time, no evidence-based recommendation can be formulated regarding frequency, intensity, or duration of exercise. Nevertheless, some first trends regarding the effects of certain types of exercise can be identified. When focusing on long-term health benefits in children and adolescents with ADHD, qualitative exercise characteristics might play an important role.

Fine motor deficits and attention deficit hyperactivity disorder in primary school children

Background

Many children with attention deficit hyperactivity disorder (ADHD) display motor deficiencies during their daily routine, which may have impact on their developmental course. Children with ADHD who experience motor deficiencies often display deficits in tasks requiring movements, such as handwriting.

Aim

This study investigated deficiencies in fine motor skills in primary school children with ADHD. The study further sought to establish whether ADHD subtypes differ in deficiencies of fine motor performance, recorded for both the dominant and non-dominant hands.

Methods

The Disruptive Behavior Disorders Rating Scale, completed by educators and parents, was used to screen for ADHD symptoms. Researchers confirmed the diagnosis of ADHD. Motor functioning was assessed using the Grooved Pegboard and Maze Coordination. The children diagnosed with ADHD were matched for age and gender with controls without ADHD. The sample consisted of an ADHD group (160) and control group (160) of primary school children from the Moletjie area.

Results

Children with ADHD (predominantly inattentive subtype) and ADHD (combined subtype) performed significantly more poorly than the control group on the Grooved Pegboard (p < 0.05) with both the dominant and non-dominant hand. No significant difference between the hyperactivity and impulsiveness subtype and the controls were found. There was no difference on the Maze Coordination Task (p > 0.05) between the ADHD subtypes and the controls.

Conclusion

Difficulties in fine motor skills are prevalent in children with ADHD, particularly in the ADHD-PI and ADHD-C. Problems are encountered in distal, complex, speeded tasks. The effect may lead to poor handwriting and academic performance.

Fine motor ability and psychiatric disorders in youth

Impaired fine motor ability has been linked to several domains of psychopathology. However, studies validating the specificity of this association among several categorical psychiatric disorders are still needed. The aim of this study was to assess differences in fine motor ability performance among four non-overlapping groups of psychiatric disorders and a group of typical developing comparisons (TDC). Our sample consisted of 2035 subjects aged 6-14-year-old. Diagnoses of psychiatric disorders were performed with the Development and Well-Being Assessment (DAWBA). Five non-overlapping groups without comorbidity were formed: phobic disorders (n = 101), distress disorders (n = 82), attention deficit hyperactivity disorder (ADHD) (n = 133), oppositional defiant disorder/conduct disorder (ODD/CD) (n = 52) and one group of typical developing comparisons (TDC) (n = 1667). Fine motor ability was evaluated by three tasks: sequential finger-thumb opposition, Oseretsky, and pronation/supination tests. Each task was assessed by total time to perform the movement and levels of accuracy, fluency, symmetry, precision, and coordination. We found that, when compared to TDC, the ADHD group performed more poorly in total fine motor ability (mean difference = - 0.28; p = 0.014), time to complete the task (mean difference = 0.36; p < 0.001), accuracy (mean difference = - 0.30; p = 0.005), fluency (mean difference = - 0.26; p = 0.03), symmetry (mean difference - 0.25; p = 0.04), precision (mean difference = - 0.26; p = 0.026), and coordination (mean difference = - 0.25; p = 0.042). The ADHD group also took more time to complete the task than the ODD/CD group (mean difference = 0.45; p = 0.037). No other significant between-group differences were found. Additional analyses showed those differences were statistically significant for all ADHD dimensions. Our results suggest that children with ADHD present impairments in all aspects of fine motor abilities compared to TDC, a difference not found in other psychiatric disorders.

Prevalence and Correlates of ADHD Among Adolescent Students in Nigeria

OBJECTIVE

To determine the prevalence and psychosocial correlates of ADHD among adolescents in Jos, Nigeria.

METHOD

A cross-sectional descriptive two-stage study of 487 randomly selected participants using Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL), Raven's Standard Progressive Matrix (SPM) and the Children's Global Assessment Score (CGAS).

RESULTS

The prevalence of ADHD was 8.8%. The subtypes found were inattentive (3.08%), hyperactive-impulsive (2.05%), and combined (3.08%); male:female ratio of 1.4:1. ADHD was significantly associated with use of substance by father (odds ratio [OR] = 0.35; 95% confidence interval [CI] = [0.154, 0.781]), use of substance by mother (OR = 0.2; 95% CI = [0.055, 0.711]), and lower education of mother (OR = 0.3 95% CI = [0.116, 0.693]). Poor quality of handwriting (χ² = 8.120; p = .010) and impaired global functioning ( t test = 10.756; p < .001) were significantly associated with ADHD in the adolescents.

CONCLUSION

Given the burden of ADHD, efforts should be made to establish a system for the early identification and management.

Upper limb function in children with attention-deficit/hyperactivity disorder (ADHD)

Upper limb function was investigated in children with ADHD using objective methods. We hypothesised that children with ADHD exhibit abnormal dexterity, force application during manipulation of a novel object, and movement rhythmicity. Two groups of age- and gender-matched children were investigated: 35 typically developing children (controls, 10.5 ± 0.4 years, 32M-3F) and 29 children (11.5 ± 0.5 years, 27M-2F) with formally diagnosed ADHD according to DSM-IV-TR criteria. Participants underwent a series of screening tests and tests of upper limb function while "off" medication. Objective quantification of upper limb function involved measurement of force during a grip and lift task, maximal finger tapping task, and maximal pinch grip. Acceleration at the index finger was also measured during rest, flexion and extension, and a postural task to quantify tremor. The Movement Assessment Battery for Children-2 (MABC-2) was also administered. Significant between-group differences were observed in movement rhythmicity, manipulation of a novel object, and performance of the MABC-2 dexterity and aiming and catching components. Children with ADHD lifted a novel object using a lower grip force (P = 0.036), and held the object with a more variable grip force (P = 0.003), than controls. Rhythmicity of finger tapping (P = 0.008) and performance on the dexterity (P = 0.007) and aiming and catching (P = 0.042) components of the MABC-2 were also significantly poorer in the ADHD group than controls. Movement speed, maximum pinch grip strength, and tremor were unaffected. The results of the study show for the first time that ADHD is associated with deficits in multiple, but not all domains of upper limb function.

False Memory in Adults With ADHD: A Comparison Between Subtypes and Normal Controls

OBJECTIVES

To examine the performance on the Deese-Roediger-McDermott task of adults divided into ADHD subtypes and compares their performance to that of healthy controls to examine whether adults with ADHD are more susceptible to the production of false memories under experimental conditions.

METHOD

A total of 128 adults with ADHD (50% females), classified into three Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV-TR) subtypes, were compared with 48 controls.

RESULTS

The results indicated that the ADHD participants recalled and recognized fewer studied words than the controls, the ADHD groups produced more false memories than the control group, no differences in either the false positives or the false negatives. The ADHD-combined (ADHD-CT) group recognized significantly more critical words than the control, ADHD-predominantly inattentive (ADHD-IA), and ADHD-predominantly hyperactive-impulsive (ADHD-HI) groups. The ADHD groups recalled and recognized more false positives, were more confident in their false responses, and displayed more knowledge corruption than the controls. The ADHD-CT group recalled and recognized more false positives than the other ADHD groups.

CONCLUSION

The adults with ADHD have more false memories than the controls and that false memory formation varied with the ADHD subtypes.

Neurological soft signs, but not theory of mind and emotion recognition deficit distinguished children with ADHD from healthy control

Attention Deficit Hyperactivity Disorder (ADHD) is associated with social cognition impairment, executive dysfunction and motor abnormalities, consisting in the persistence of neurological soft signs (NSS). Theory of mind (ToM) and emotion recognition (ER) deficit of children with ADHD have been interpreted as a consequence of their executive dysfunction, particularly inhibitory control deficit. To our knowledge, there are not studies that evaluate the possible correlation between the ToM and ER deficit and NSS in the population with ADHD, while this association has been studied in other psychiatric disorders, such as schizophrenia. Therefore, the aim of this study was to evaluate ToM and ER and NSS in a sample of 23 drug-naïve children with ADHD and a sample of 20 healthy children and the possible correlation between social cognition dysfunction and NSS in ADHD. Our findings suggest that ToM and ER dysfunction is not a constant feature in the population with ADHD, while NSS confirmed as a markers of atypical neurodevelopment and predictors of the severity of functional impairment in children with ADHD.

Attention Deficit Hyperactivity Disorder and Motor Impairment

Attention deficit hyperactivity disorder (ADHD) is the most common neurobehavioral disorder during childhood, affecting approximately 3–6% of school-aged children; its cardinal symptoms of high activity, impulsivity, and behavioral distractibility might be assumed to have close relationships to interferences with motor skills. A separate body of literature attests to ways that motor problems can severely impact children’s daily lives, as motor problems may occur in 30–50% of children with ADHD. This article critically reviews research on motor impairment in children with ADHD, notable differences in motor performance of individuals with ADHD compared with age-matched controls, and possible neural underpinnings of this impairment. We discuss the highly prevalent link between ADHD and developmental coordination disorder (DCD) and the lack of a clear research consensus about motor difficulties in ADHD. Despite increasing evidence and diagnostic classifications that define DCD by motor impairment, the role of ADHD symptoms in DCD has not been delineated. Similarly, while ADHD may predispose children to motor problems, it is unclear whether any such motor difficulties observed in this population are inherent to ADHD or are mediated by comorbid DCD. Future research should address the exact nature and long-term consequences of motor impairment in children with ADHD and elucidate effective treatment strategies for these disorders together and apart.

Poor performance of fine motor activity among biological parents of children with attention deficit/hyperactivity disorder

It has been proposed that the dopaminergic system and heritability may play roles in attention deficit/hyperactivity disorder (ADHD). We assessed the performance of healthy parents of children with ADHD in the finger tapping test (FTT) in this study, which is a reliable test and sensitive to central dopamine activity. A total of 16 parents of children with ADHD and 32 controls were enrolled. The FTT was conducted. The 16 healthy parents of children with ADHD exhibited a significantly poorer performance in the FTT, using the nondominant hand, than the 32 healthy controls. This finding indicated that poor motor function could be a potential characteristic in parents of offspring with ADHD.

Neurological soft signs are associated with attentional dysfunction in children with attention deficit hyperactivity disorder

INTRODUCTION

Inattention is one of the core symptoms of Attention Deficit Hyperactivity Disorder (ADHD). Most of patients with ADHD show motor impairment, consisting in the persistence of neurological soft signs (NSS). Our aim was to evaluate attentional and motor functioning in an ADHD sample and healthy children (HC) and possible link between attentional dysfunction and motor impairment in ADHD.

METHOD

Twenty-seven drug-naive patients with ADHD and 23 HC were tested with a test battery, measuring different aspects of attention. Motor evaluation has provided three primary variables: overflow movements (OM), dysrhythmia and total speed of timed activities.

RESULTS

Compared to HC, patients were impaired in a considerable number of attentional processes and showed a greater number of NSS. Significant correlations between disturbances of attention and motor abnormalities were observed in ADHD group.

CONCLUSION

Our findings suggest that attentional processes could be involved in the pathophysiology of the NSS and add scientific evidence to the predictive value of NSS as indicators of the severity of functional impairment in ADHD. Given the marked improvement or complete resolution of NSS following treatment with methylphenidate, we suggest that evaluation of NSS is useful to monitor the effectiveness of pharmacological treatment with MPH in ADHD.

A decade of contributions to understanding and ameliorating attention deficit-hyperactivity disorder

Background

It has been 10 years since Terje Sagvolden founded Behavioral and Brain Functions.

Body

After setting the context, this paper reviews some of the contributions of articles in the journal to the literature on ADHD over that decade. Those articles provide a cross section of some of the most important ongoing themes in ADHD research.

Conclusion

Terje’s faith in the new journal was well founded. It has survived the first threat of new journals, crib death, because of the continuing quality and relevance of the articles it carries. It has a diversified portfolio of similar research in many other fields of related interest.

Motor abilities of children and adolescents with a psychiatric condition: A systematic literature review

AIM: To summarize research regarding the motor abilities of children and adolescents who suffer from a common psychiatric condition.

METHODS: In order to outline the current knowledge regarding the motor abilities of children and adolescents with autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), disruptive behavior disorders (DBD) and depression, a comprehensive systematic literature search was carried out using PubMed, Medline and ERIC databases. The databases were searched for relevant English language articles published between January 1990 and April 2014. Only studies that conducted a quantitative evaluation of motor ability and concerned individuals aged 0-18 years were included. A separate search was conducted for each disorder (ASD, ADHD, DBD, depression) in conjunction with each of the following keywords: (psycho/perceptuo) motor/movement skill(s), (psycho/perceptuo) motor/movement abilities, (psycho/perceptuo) motor/movement impairment, (psycho/perceptuo) motor/movement problem(s), motor function, motor coordination, motor performance, motor deficit(s). To detect supplementary relevant literature, the reference lists of the retrieved articles were examined.

RESULTS: The search strategy yielded 51 studies meeting the inclusion criteria. In total, 28 studies were included that examined the motor abilities of children and adolescents with ASD. All studies indicated that they performed below average on various standardized motor assessment instruments. The overall prevalence rate for impairment in motor abilities ranged from 33% to 100%. Twenty-seven studies examined the motor abilities of children and adolescents with ADHD. Depending on the type of motor assessment tool and the cut-off points used by different researchers, prevalence rates of impairment in motor abilities are highly variable and ranged from 8% to 73%. Remarkably, there is a paucity of research addressing the motor abilities of individuals with DBD or depression. Furthermore, methodological problems, such as measurement and comorbidity issues, complicate the generalization of the findings.

CONCLUSION: Research suggests that motor impairment is highly prevalent in some psychiatric conditions, particularly ASD and ADHD. However, future work is necessary to draw sound conclusions.

Development of graphomotor fluency in adults with ADHD: Evidence of attenuated procedural learning

PURPOSE

The present study sought to determine if adults with ADHD demonstrate reduced graphomotor learning relative to controls.

METHOD

Twenty-eight control adults (n=14) and adults with ADHD (n=14) were recruited and wrote a novel grapheme on a digitizing tablet 30 times. Participants with ADHD were counterbalanced on and off stimulant medication.

RESULTS

Control participants, F(1,13)=13.786, p=.003, ω(2)partial=.460, and participants with ADHD on medication, F(1,13)=10.462, p=.007, ω(2)partial=.387, demonstrated significant improvement in graphomotor fluency with equivalent practice whereas participants with ADHD off medication did not, F(1,12)=0.166, NS.

CONCLUSIONS

Results indicate that graphomotor program learning in adults with ADHD may occur more slowly than typically developing peers. Findings have implications for providing accommodations to adults with ADHD, potential benefits of stimulant medication, and using digitizing technology as a neuropsychological assessment instrument.

Neurological soft signs in children with attention deficit hyperactivity disorder: Their relationship to executive function and parental neurological soft signs

The correlations between neurological soft signs (NSS) in children with attention deficit hyperactivity disorder (ADHD) and their executive function, symptoms of inattention, and hyperactivity-impulsivity and the NSS of their parents remain unclear. This study aimed to examine: (1) the prevalence of NSS in children with ADHD and their parents; (2) the correlation between the NSS of children with ADHD and the NSS of their parents; and (3) the correlation between the NSS of children with ADHD and their executive function and symptoms. NSS were assessed with the Cambridge Neurological Inventory (CNI) in 57 children with ADHD (and 80 parents) and 60 healthy children (and 75 parents). Executive function was measured with the Behavioral Rating Inventory of Executive Function (BRIEF). Children with ADHD and their parents had significantly higher NSS than normal children and their parents, respectively, and the NSS of children with ADHD were correlated more strongly with the NSS of their fathers than their mothers. No correlation was found between NSS and BRIEF executive function, but Disinhibition in children with ADHD was significantly correlated with hyperactivity-impulsivity symptoms. Paternal and maternal NSS provided different predictions for child NSS. It may be that NSS are more likely to be genetically transmitted by fathers.

Grooved Pegboard for adult employed South Africans: normative data and human immunodeficiency virus associations

The Grooved Pegboard is a widely used test of psychomotor speed, and currently is used in particular to assess HIV-associated neurocognitive decline. To accurately interpret any assessment, appropriate reference norms are required. Although South Africa has the highest number of people living with HIV and AIDS, no local large scale reference data are available for the Grooved Pegboard. The main objective of the study was to formulate reference data for healthy adult South Africans in formal employment; two secondary objectives aimed to statistically explore the available Grooved Pegboard performance data, as well as its association with HIV status. Data were collected as part of multi-disciplinary occupational health screening, and included healthy HIV− adults ( N = 3118), and 70 HIV+ participants. This article presents normative reference data stratified across age and gender categories. The South African scores differ from other reported samples, emphasising the need to develop local norms that are context based, to facilitate clinical interpretation of psychomotor performance. Furthermore, in this sample, the Grooved Pegboard differentiated significantly between asymptomatic HIV+ persons, and those with HIV-associated neurocognitive disorders, although with poor predictive ability. In conclusion, large-sample reference data for healthy employed adult South Africans (age 19–59) are reported across gender and age categories, and may assist in more accurate screening of psychomotor speed generally, and HIV-associated neurocognitive decline in particular.

The four causes of ADHD: a framework

In addition to the symptoms singled out by the diagnostic criteria for Attention-Deficit Hyperactivity Disorder (ADHD), a comprehensive definition should inform us of the events that trigger ADHD in both its acute and chronic manifestations; the neurobiology that underlies it; and the evolutionary forces that have kept it in the germ line of our species. These factors are organized in terms of Aristotle's four kinds of "causes," or explanations: formal, efficient, material, and final. This framework systematizes the nosology, biology, psychology, and evolutionary pressures that cause ADHD.

Motor skills in Czech children with attention-deficit/hyperactivity disorder and their neurotypical counterparts

Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed neurobehavioural disorder. Characterized by recurring problems with impulsiveness and inattention in combination with hyperactivity, motor impairments have also been well documented in the literature. The aim of this study was to compare the fine and gross motor skills of male and female children with ADHD and their neurotypical counterparts within seven skill assessments. This included three fine motor tasks: (1) spiral tracing, (2) dot filling, (3) tweezers and beads; and four gross motor tasks: (1) twistbox, (2) foot tapping, (3) small plate finger tapping, and (4) large plate finger tapping. It was hypothesized that children with ADHD would display poorer motor skills in comparison to neurotypical controls in both fine and gross motor assessments. However, statistically significant differences between the groups only emerged in four of the seven tasks (spiral tracing, dot filling, tweezers and beads and foot tapping). In line with previous findings, the complexity underlying upper limb tasks solidified the divide in performance between children with ADHD and their neurotypical counterparts. In light of similar research, impairments in lower limb motor skill were also observed. Future research is required to further delineate trends in motor difficulties in ADHD, while further investigating the underlying mechanisms of impairment.

A comparison of phenylketonuria with attention deficit hyperactivity disorder: do markedly different aetiologies deliver common phenotypes?

Phenylketonuria (PKU) is a well-defined metabolic disorder arising from a mutation that disrupts phenylalanine metabolism and so produces a variety of neural changes indirectly. Severe cognitive impairment can be prevented by dietary treatment; however, residual symptoms may be reported. These residual symptoms appear to overlap a more prevalent childhood disorder: Attention Deficit/Hyperactivity Disorder (ADHD). However, the aetiology of ADHD is a vast contrast to PKU: it seems to arise from a complex combination of genes; and it has a substantial environmental component. We ask whether these two disorders result from two vastly different genotypes that converge on a specific core phenotype that includes similar dysfunctions of Gray's (Gray, 1982) Behavioural Inhibition System (BIS), coupled with other disorder-specific dysfunctions. If so, we believe comparison of the commonalities will allow greater understanding of the neuropsychology of both disorders. We review in detail the aetiology, treatment, neural pathology, cognitive deficits and electrophysiological abnormalities of PKU; and compare this with selected directly matching aspects of ADHD. The biochemical and neural pathologies of PKU and ADHD are quite distinct in their causes and detail; but they result in the disorder in the brain of large amino acid levels, dopamine and white matter that are very similar and could explain the overlap of symptoms within and between the PKU and ADHD spectra. The common deficits affect visual function, motor function, attention, working memory, planning, and inhibition. For each of PKU and ADHD separately, a subset of deficits has been attributed to a primary dysfunction of behavioural inhibition. In the case of ADHD (excluding the inattentive subtype) this has been proposed to involve a specific failure of the BIS; and we suggest that this is also true of PKU. This accounts for a substantial proportion of the parallels in the superficial symptoms of both disorders and we see this as linked to prefrontal, rather than more general, dysfunction of the BIS.

Sensory and motor secondary symptoms as indicators of brain vulnerability

In addition to the primary symptoms that distinguish one disorder from the next, clinicians have identified, yet largely overlooked, another set of symptoms that appear across many disorders, termed secondary symptoms. In the emerging era of systems neuroscience, which highlights that many disorders share common deficits in global network features, the nonspecific nature of secondary symptoms should attract attention. Herein we provide a scholarly review of the literature on a subset of secondary symptoms––sensory and motor. We demonstrate that their pattern of appearance––across a wide range of psychopathologies, much before the full-blown disorder appears, and in healthy individuals who display a variety of negative symptoms––resembles the pattern of appearance of network abnormalities. We propose that sensory and motor secondary symptoms can be important indicators of underlying network aberrations and thus of vulnerable brain states putting individuals at risk for psychopathology following extreme circumstances.

Genetic variation in dopamine-related gene expression influences motor skill learning in mice

Several neurodevelopmental disorders with a strong genetic basis, including attention-deficit/hyperactivity disorder, autism spectrum disorders and developmental coordination disorder, involve deficits in fine motor skills. This phenotype may depend on heritable variation in components of the dopamine (DA) system, which is known to play a critical role in motor skill learning. In this study, we took advantage of two inbred strains of mice (BALB/c and C57BL/6) that differ markedly in the number of midbrain DA neurons in order to investigate the influence of such naturally occurring genetic variation on the acquisition and performance of fine motor skills. Gene expression analysis of midbrain, frontal cortex and striatum showed significant differences in the expression of presynaptic and postsynaptic dopaminergic (DAergic) markers (e.g. tyrosine hydroxylase, DA transporter, DA D4 receptor, DA D5 receptor and DARPP-32) between these two strains. BALB/c mice had lower learning rate and performance scores in a complex skilled reaching task when compared with C57BL/6 mice. A negative correlation was found between the motor learning rate and level of DARPP-32 mRNA expression in the frontal cortex contralateral to the trained forelimb. The rate of motor learning was also negatively correlated with the levels of DARPP-32 and DA D1 receptor mRNAs in the striatum. Our results suggest that genetically driven variation in frontostriatal DAergic neurotransmission is a major contributor to individual differences in motor skill learning. Moreover, these findings implicate the D1R/cAMP/DARPP-32 signaling pathway in those neurodevelopmental disorders that are associated with fine motor skill deficits.

Advanced analysis of finger-tapping performance: a preliminary study

BACKGROUND

The finger-tapping test is a commonly employed quantitative assessment tool used to measure motor performance in the upper extremities. This task is a complex motion that is affected by external stimuli, mood and health status. The complexity of this task is difficult to explain with a single average intertap-interval value (time difference between successive tappings) which only provides general information and neglects the temporal effects of the aforementioned factors.

AIMS

This study evaluated the time course of average intertap-interval values and the patterns of variation in both the right and left hands of right-handed subjects using a computer-based finger-tapping system.

STUDY DESIGN

Cross sectional study.

METHODS

Thirty eight male individuals aged between 20 and 28 years (Mean±SD = 22.24±1.65) participated in the study. Participants were asked to perform single-finger-tapping test for 10 seconds of test period. Only the results of right-handed (RH) 35 participants were considered in this study. The test records the time of tapping and saves data as the time difference between successive tappings for further analysis. The average number of tappings and the temporal fluctuation patterns of the intertap-intervals were calculated and compared. The variations in the intertap-interval were evaluated with the best curve fit method.

RESULTS

An average tapping speed or tapping rate can reliably be defined for a single-finger tapping test by analysing the graphically presented data of the number of tappings within the test period. However, a different presentation of the same data, namely the intertap-interval values, shows temporal variation as the number of tapping increases. Curve fitting applications indicate that the variation has a biphasic nature.

CONCLUSION

The measures obtained in this study reflect the complex nature of the finger-tapping task and are suggested to provide reliable information regarding hand performance. Moreover, the equation reflects both the variations in and the general patterns associated with the task.

A behavioral neuroenergetics theory of ADHD

Energetic insufficiency in neurons due to inadequate lactate supply is implicated in several neuropathologies, including attention-deficit/hyperactivity disorder (ADHD). By formalizing the mechanism and implications of such constraints on function, the behavioral Neuroenergetics Theory (NeT) predicts the results of many neuropsychological tasks involving individuals with ADHD and kindred dysfunctions, and entails many novel predictions. The associated diffusion model predicts that response times will follow a mixture of Wald distributions from the attentive state, and ex-Wald distributions after attentional lapses. It is inferred from the model that ADHD participants can bring only 75-85% of the neurocognitive energy to bear on tasks, and allocate only about 85% of the cognitive resources of comparison groups. Parameters derived from the model in specific tasks predict performance in other tasks, and in clinical conditions often associated with ADHD. The primary action of therapeutic stimulants is to increase norepinephrine in active regions of the brain. This activates glial adrenoceptors, increasing the release of lactate from astrocytes to fuel depleted neurons. The theory is aligned with other approaches and integrated with more general theories of ADHD. Therapeutic implications are explored.

Task-dependent interactions between dopamine D2 receptor polymorphisms and L-DOPA in patients with Parkinson's disease

Variants in genes regulating dopamine transmission affect performance on tasks including working memory and executive function as well as temporal processing and sequence learning. In the current study, we determined whether a dopamine D2 receptor DNA sequence polymorphism interacts with L-DOPA during motor tasks in patients with Parkinson's disease (PD). Forty-five PD patients were genotyped for the DRD2 polymorphism (rs 1076560, G>T). Patients performed an explicit motor sequence learning task and the grooved pegboard test in both ON and OFF L-DOPA states. For motor sequence learning, DRD2 genotype mediated L-DOPA effects such that L-DOPA associated improvements were only observed in the minor T allele carriers (associated with lower D2 receptor availability, t10=-2.71, p=0.022), whereas G homozygotes showed no performance change with L-DOPA. For the grooved pegboard test, performance improved with L-DOPA independent of patients' DRD2 genotype. Collectively these results demonstrate that common DRD2 allelic differences found in the human population may explain how dopamine differentially contributes to performance across tasks and individuals.

Effects of sensory information, movement direction, and hand use on fine motor precision

The differences in fine motor precision over line model in different sensorial conditions (visual-proprioceptive and proprioceptive only) for different movement directions (transverse, frontal, and sagittal) and both hands were measured digitally with use of special software. The observed variables were directional (D) and formal (F) deviations, together with changes of line length (LL) from the base model. Analysis indicated non-significant differences for all measured variables for hand use, while for the remaining factors (sensory test condition and movement direction), the differences were significant for all levels. Both sensory information and movement directions are important for hand-drawing precision, not just the specific hand used.

Neuropsychological testing in a rural African school-age population: evaluating contributions to variability in test performance

This study investigated the psychometric properties of a number of neuropsychological tests adapted for use in sub-Saharan Africa. A total of 308 school-age children in a predominantly rural community completed the tests. These tests were developed to assess skills similar to those measured by assessments of cognitive development published for use in Western contexts. Culturally appropriate adaptations were made to enhance within-population variability. Internal consistency ranged from .70 to .84. Scores on individual tests were related to various background factors at the level of the child, household, and neighborhood. School experience was the most consistent predictor of outcome, accounting for up to 22.9% of the variance observed. Significant associations were identified to determine salient background characteristics that should be taken into account when measuring the discrete effects of disease exposure in similar sociocultural and economic settings.

Central processing energetic factors mediate impaired motor control in ADHD combined subtype but not in ADHD inattentive subtype

Participants with attention-deficit/hyperactivity disorder (ADHD) are often impaired in visuomotor tasks. However, little is known about the contribution of modal impairment in motor function relative to central processing deficits or whether different processes underlie the impairment in ADHD combined (ADHD-C) versus ADHD inattentive (ADHD-I) subtype. The present study analyzes performance on the Visual Motor Integration Test relative to less effortful motor tests as well as on measures of energetics. Both ADHD groups showed evidence of impaired motor function on both visual-motor integration (VMI) and the less effortful motor tests. The ADHD-C group performed below the ADHD-I group on VMI, but their performance correlated highly with the measures of the energetic pools of arousal and effort. Different mechanisms may underlie impaired fine motor skills in ADHD. Central processing deficits contribute significantly to the deficit of ADHD-C but do not explain the motor impairment in ADHD-I.

Linkages between childhood executive functioning and adolescent social functioning and psychopathology in girls with ADHD

We followed an ethnically and socioeconomically diverse sample of preadolescent girls with ADHD (n = 140) and matched comparison girls (n = 88) over a period of 5 years, from middle childhood through early/midadolescence, with the aim of determining whether childhood levels of executive function (EF) would predict adolescent multi-informant outcomes of social functioning and psychopathology, including comorbidity between externalizing and internalizing symptomatology. Predictors were well-established measures of planning, response inhibition, and working memory, along with a control measure of fine motor control. Independent of ADHD versus comparison group status, (a) childhood planning and response inhibition predicted adolescent social functioning and (b) childhood planning predicted comorbid internalizing/externalizing disorders in adolescence. Subgroup status (ADHD-Combined, ADHD-Inattentive, and comparison) moderated the relationship between childhood planning and adolescent internalizing/externalizing comorbidity, with the combined type revealing particularly strong associations between baseline planning and adolescent comorbidity. Mediation analyses indicated that adolescent social functioning mediated the prediction from childhood EF to comorbidity at follow-up; in turn, in the girls with ADHD, adolescent comorbidity mediated the prediction from childhood EF to social functioning at follow-up. We conclude that childhood interventions should target EF impairments in addition to behavioral symptoms.

ADHD: volumetry, motor, and oculomotor functions

The use of quantitative neuroimaging (volumetry), motor, and oculomotor assessments for studying children with attention-deficit/hyperactivity disorder (ADHD) has grown dramatically in the past 20 years. Most evidence to date suggests that anomalous basal ganglia development plays an important role in early manifestation of ADHD; however, widespread cerebellar and cortical delays are also observed and are associated with the behavioral (cognitive, motor, oculomotor) phenotype in children with ADHD. These motor and "executive" control systems appear to develop in parallel, such that both systems display a similar protracted developmental trajectory, with periods of rapid growth in elementary years and continued maturation into young adulthood. Development of each system is dependent on the functional integrity and maturation of related brain regions, suggesting a shared neural circuitry that includes frontostriatal systems and the cerebellum (i.e., those identified as anomalous in studies of volumetry in ADHD). Motor and oculomotor paradigms provide unique opportunities to examine executive control processes that exist at the interface between movement and cognition in children with ADHD, also linking cognition and neurological development. The observed pattern of volumetric differences, together with the known parallel development of motor and executive control systems, appears to predict motor and oculomotor anomalies in ADHD, which are highly relevant, yet commonly overlooked in clinical settings.

Deficits in fine motor skills in a genetic animal model of ADHD

Background

In an attempt to model some behavioral aspects of Attention Deficit/Hyperactivity Disorder (ADHD), we examined whether an existing genetic animal model of ADHD is valid for investigating not only locomotor hyperactivity, but also more complex motor coordination problems displayed by the majority of children with ADHD.

Methods

We subjected young adolescent Spontaneously Hypertensive Rats (SHRs), the most commonly used genetic animal model of ADHD, to a battery of tests for motor activity, gross motor coordination, and skilled reaching. Wistar (WIS) rats were used as controls.

Results

Similar to children with ADHD, young adolescent SHRs displayed locomotor hyperactivity in a familiar, but not in a novel environment. They also had lower performance scores in a complex skilled reaching task when compared to WIS rats, especially in the most sensitive measure of skilled performance (i.e., single attempt success). In contrast, their gross motor performance on a Rota-Rod test was similar to that of WIS rats.

Conclusion

The results support the notion that the SHR strain is a useful animal model system to investigate potential molecular mechanisms underlying fine motor skill problems in children with ADHD.

Motor function and methylphenidate effect in children with attention deficit hyperactivity disorder

AIM

Hyperactivity, impulsivity and poor attention are the core problems of ADHD and central stimulant medication is the preferred treatment. Many children with ADHD also display motor problems. The present study investigated the presence of motor problems in subjects who showed positive response to central stimulants on ADHD symptoms, compared with non-responders.

METHOD

This is a retrospective study of 73 children diagnosed ADHD, aged 5-17 years, who had been assessed with parts of the 'Motor Function Neurological Assessment' (MFNU) and evaluated with regard to effect of central stimulant medication. The sample was divided into two subgroups based on the responses to methylphenidate: Medicine responders and Non medicine responders.

RESULTS

Stimulant responders showed significantly more motor problems than the non-responders on all sub-tests and on the total problem score of the MFNU. Motor problems were present both in younger (age 5-10 years) and older (11-17 years) stimulant responders. There were no gender differences in motor performance.

CONCLUSION

Our findings indicate that the probability of positive effect of central stimulants on core problems of ADHD is higher when motor problems are present in addition to ADHD symptoms, than when motor problems are absent.

Pathophysiology of NSS in ADHD

Attention deficit/hyperactivity disorder (ADHD) is the behavioural disorder most commonly diagnosed in childhood. In addition to the main symptoms of inattention, impulsiveness and hyperactivity, neurological soft signs (NSS) are often associated with ADHD. NSS are discrete motor and sensory disorders that cannot be linked to specific cerebral lesions. We review all the scientific contributions on NSS in ADHD. The conclusions support the presence of an alteration in the neural networks for motor control inhibition, at the base of the pathophysiology of NSS in children with ADHD, as well as a possible central role of dopamine in these neural circuits.

Motor function may differentiate attention deficit hyperactivity disorder from early onset bipolar disorder

BACKGROUND

Differentiating between bipolar spectrum disorder (BD) and attention deficit hyperactivity disorder (ADHD) in childhood and adolescence is difficult because the clinical presentation is influenced by ongoing neural development, causing considerable symptom overlap. Motor problems and neurological soft signs have been associated with ADHD for decades. Little is known about motor skills in BD. Here we assess the diagnostic accuracy of neuromotor deviations in differentiating ADHD from BD in clinical practice. We also investigate if these deviations exist in concurrent ADHD and BD, thus indicating true comorbidity

METHODS

64 patients 6-18 years (31 girls, 33 boys) fulfilling the diagnostic criteria of BD, ADHD combined subtype (ADHD-C) or comorbid BD and ADHD-C, were compared using an age-standardized neuromotor test; NUBU. Categorical variables were analyzed using cross table with two-tailed chi square test or Fisher's exact test when appropriate. Continuous variables were analyzed by Kruskal-Wallis test and, if significant, Mann-Whitney U test and ROC plots.

RESULTS

The ADHD-C group and the comorbid ADHD-C and BD group both showed significantly more neurological soft signs (p less than 0.01) and lower mean static coordination percentile (p less than 0.01) than the BD group. The positive predictive value of NUBU in the diagnosis of ADHD-C with or without concurrent BD was 89% (80-95) for total soft signs and 87% (79-95) for static coordination below the 7.5 percentile.

CONCLUSION

An age-standardized neuromotor test battery may promote diagnostic accuracy in differentiating ADHD from BD in clinical practice, and help evaluating whether symptoms of ADHD in children who have BD reflect symptom overlap or real comorbidity. This may have important implications for everyday diagnostic work.

Distinct response time distributions in attention deficit hyperactivity disorder subtypes

OBJECTIVE

To address the issue of response time (RT) profiles in hyperactive-impulsive (ADHD-HI), inattentive (ADHD-IA), and combined (ADHD-C) subtypes of ADHD. We hypothesized that children with ADHD-HI should respond more rapidly than children without ADHD and children with ADHD-IA and ADHD-C should respond more slowly than children without ADHD.

METHOD

Four groups (3 ADHD groups and 1 non-ADHD group) each composed of 16 children (7-13 years old) performed a visuospatial choice task.

RESULTS

ANOVA indicated very variable RTs for each ADHD subtype when controlling for individual RT. ANOVA performed on RT distribution showed significant differences between the ADHD and non-ADHD groups: biased to fast responses in ADHD-HI and biased to slow responses in ADHD-IA and ADHD-C.

CONCLUSION

The results suggest that response time profiles were abnormal in all ADHD subtypes and were markedly different between children meeting criteria for ADHD-HI and those meeting criteria for ADHD-IA or ADHD-C.

The Motor Function Neurological Assessment (MFNU) as an indicator of motor function problems in boys with ADHD

BACKGROUND

The paper presents the Motor Function Neurological Assessment (MFNU), as a tool for identifying typical motor function problems in children with Attention Deficit Hyperactivity Disorder (ADHD). The study investigated motor functions in boys diagnosed with Hyperkinetic Disorder (HKD, F.90.0). HKD corresponds to the ADHD-combined (ADHD-C) diagnosis in the DSM-IV. The paper addresses the ability of the instrument to discriminate between non-medicated boys with HKD and a control group consisting of normal non-referred boys without any clinical significant ADHD symptoms.

METHODS

25 drug-naïve boys, aged 8-12 years and recently diagnosed as HKD F90.0, were compared with 27 controls, all boys in the same age range, on 17 MFNU subtests, and with a 'Total score' parameter.

RESULTS

On the individual subtests 80-96% (median 88%) of the ADHD group showed 'moderate' to 'severe' problems, compared to 0-44% (median 14.8%) within the control group. The percentage of 'severe problems' ranged from 44-84%, (median 64%) in the ADHD group, and 0-44% (median 0%) in the control group. The highly significant differences found between the groups on all subtests, and on the Total score scores, indicated that the MFNU had a high discriminative power when children with ADHD and normal controls were compared. The Total score parameter seemed to be a meaningful discriminator of a common underlying factor of the 17 subtests used in the study.

CONCLUSION

The study confirms our clinical findings that the MFNU measures a consistent pattern of motor function problems in children with HKD, and that these problems are rarely represented in individuals without ADHD. Further research is needed to investigate to what extent the MFNU taps motor problems that are truly specific to ADHD, in contrast to motor problems common to children with DCD or other clinical problems.

The effect of sequel symptoms and signs of Complex Regional Pain Syndrome type 1 on upper extremity disability and quality of life

Although properly treated, patients with Complex Regional Pain Syndrome type 1 (CRPS type 1) of upper limb may continue to have sequel signs and symptoms of the disease in long-term. The aim of this study is to analyse the effect of the sequel findings of CRPS type 1 on upper limb disability and quality of life. Thirty patients with CRPS type 1 of the upper extremity were re-evaluated for the sequel sign and symptoms of CRPS type 1 after 18 months (8-60 months). Pain, range of motion, strength, manual dexterity and touch perception thresholds of the hands, upper extremity disability [Disability of arm, shoulder and hand (DASH) questionnaire] and health-related quality of life [Short Form-36 (SF-36)] were measured and compared to 38 healthy controls. Of the 30 patients, only 3 patients (10%) were symptom free. Pain after use was the most frequently found symptom. Strength and range of motion of the involved hand was reduced in CRPS type 1 patients. Manual dexterity was impaired and touch perception threshold was elevated in CRPS type 1 patients. The involved upper extremities were more disabled in CRPS type 1 patients than controls. The severity of the pain, and numbness of the hands were the factors causing disability. Pain caused reduced quality of life in physical functioning. In conclusion, prolonged follow-up period and efforts to improve sensory disturbances (especially pain) may reduce the upper extremity disability and reduced quality of life in CRPS type 1 patients.

Relationship between endophenotype and phenotype in ADHD

Background

It has been hypothesized that genetic and environmental factors relate to psychiatric disorders through the effect of intermediating, vulnerability traits called endophenotypes. The study had a threefold aim: to examine the predictive validity of an endophenotypic construct for the ADHD diagnosis, to test whether the magnitude of group differences at the endophenotypic and phenotypic level is comparable, and to investigate whether four factors (gender, age, IQ, rater bias) have an effect (moderation or mediation) on the relation between endophenotype and phenotype.

Methods

Ten neurocognitive tasks were administered to 143 children with ADHD, 68 non-affected siblings, and 120 control children (first-borns) and 132 children with ADHD, 78 non-affected siblings, and 113 controls (second-borns) (5 – 19 years). The task measures have been investigated previously for their endophenotypic viability and were combined to one component which was labeled 'the endophenotypic construct': one measure representative of endophenotypic functioning across several domains of functioning.

Results

The endophenotypic construct classified children with moderate accuracy (about 50% for each of the three groups). Non-affected children differed as much from controls at the endophenotypic as at the phenotypic level, but affected children displayed a more severe phenotype than endophenotype. Although a potentially moderating effect (age) and several mediating effects (gender, age, IQ) were found affecting the relation between endophenotypic construct and phenotype, none of the effects studied could account for the finding that affected children had a more severe phenotype than endophenotype.

Conclusion

Endophenotypic functioning is moderately predictive of the ADHD diagnosis, though findings suggest substantial overlap exists between endophenotypic functioning in the groups of affected children, non-affected siblings, and controls. Results suggest other factors may be crucial and aggravate the ADHD symptoms in affected children.