Combined Attention Deficit Hyperactivity Disorder Research Articles

922 Association Between the Polymorphism of Drd4Exoniii48Bp Vntr and Executive Function in Han Chinese Children with Tourette's Syndrome

Objective: The relationship of DRD4exonIII48bp VNTR and executive function were studied in 86 children with Tourette's Syndrome. Methods: 86 Han Chinese children with GTS were tested using a set of neuropsychological test(Stroop test, trail making test, modified Wisconsin Card sorting test) and compared with 51 healthy control group to understand the relationship between executive deficits and genetics. Results: Compared with normal children, The GTS group showed impairment on almost all psychological measures. In some stroop test, combined ADHD group differed from the GTS-alone group. No evidence show significantly difference among DRD4exonIII48bp VNTR and executive function. Conclusion: GTS patient has executive function deficits, these deficits may have nothing to do with DRD4exonIII48bp VNTR. For comorbid, there may be a certain influence in the executive function.

A pilot study: differential effects of methylphenidate-OROS on working memory and attention functions in children with attention-deficit/hyperactivity disorder with and without behavioural comorbidities

To examine the effects of methylphenidate-OROS (MPH-OROS) on working memory (WM) and attention functions in children with attention-deficit hyperactivity disorder (ADHD), and to investigate whether there is a differential effect in ADHD children with (ADHD+) and without (ADHD-) behavioural comorbidities. Participants included a clinic referred sample of 12 stimulant naïve school-aged children with a diagnosis of combined ADHD according to the DSM-IV criteria (6 ADHD+, 6 ADHD-), and 11 healthy children. A neuropsychological protocol was applied at three different moments: before treatment, after one those of MPH-OROS, and after one month of MPH-OROS daily treatment. The protocol was simultaneously administered to the control group. Initial differences in attention parameters between naïve children with ADHD and the control group disappeared after the first dose of MPH-OROS. For WM, one month of daily treatment was necessary to achieve this pattern of results. Both ADHD groups (ADHD+ and ADHD-) showed these differences, but there was a greater improvement in (ADHD-). MPH-OROS had an immediate effect on attention deficits, but long-term treatment was needed to improve WM to the level of healthy subjects. The presence of comorbid behavioural conditions determined a less robust response in neuropsychological performance to stimulant treatment.

The Role of Inattention and Social Perception and Performance in Two Subtypes of ADHD

This study evaluated the social perception and social functioning of children with Attention Deficit Hyperactivity Disorder-Combined (ADHD-C), ADHD-predominately inattentive (ADHD-PI), and controls. Two-hundred and seventy children with ADHD-C, ADHD-PI, or controls were evaluated using direct and indirect measures of social functioning. The ADHD-C and ADHD-PI groups showed significant differences in interpretation of emotional and nonverbal cues on a direct measure of social perception compared with controls. The number of inattentive symptoms was significantly related to poor performance for interpretation of both emotional and nonverbal cues, whereas hyperactivity and impulsivity symptoms showed a less robust relation. Children with ADHD-C were rated by parents and teachers as showing significant problems with social performance and problem behaviors compared with those with ADHD-PI or with controls. These findings show a link between inattention and social perception that is separate from impulsivity difficulties. These findings have important implications for treatment.

Perinatal risk factors interacting with catechol O‐methyltransferase and the serotonin transporter gene predict ASD symptoms in children with ADHD

Symptoms of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) often co-occur. Given the previously found familiality of ASD symptoms in children with ADHD, addressing these symptoms may be useful for genetic association studies, especially for candidate gene findings that have not been consistently replicated for ADHD. We studied the association of the catechol O-methyltransferase (COMT) Val158Met polymorphism and the serotonin transporter (SLC6A4/SERT/5-HTT) 5-HTTLPR insertion/deletion polymorphism with ASD symptoms in children with ADHD, and whether these polymorphisms would interact with pre- and perinatal risk factors, i.e., maternal smoking during pregnancy and low birth weight. Analyses were performed using linear regression in 207 Dutch participants with combined type ADHD of the International Multicenter ADHD Genetics (IMAGE) study, and repeated in an independent ADHD sample (n =439) selected from the TRracking Adolescents' Individual Lives Survey (TRAILS). Dependent variables were the total and subscale scores of the Children's Social Behavior Questionnaire (CSBQ). No significant main effects of COMT Val158Met, 5-HTTLPR, maternal smoking during pregnancy and low birth weight on ASD symptoms were found. However, the COMT Val/Val genotype interacted with maternal smoking during pregnancy in increasing stereotyped behavior in the IMAGE sample (p =.008); this interaction reached significance in the TRAILS sample after correction for confounders (p =.02). In the IMAGE sample, the 5-HTTLPR S/S genotype interacted with maternal smoking during pregnancy, increasing problems in social interaction (p =.02), and also interacted with low birth weight, increasing rigid behavior (p =.03). Findings for 5-HTTLPR in the TRAILS sample were similar, albeit for related CSBQ subscales. These findings suggest gene-environment interaction effects on ASD symptoms in children with ADHD.

Frequency of Attention Deficit in First-Episode Schizophrenia Compared to ADHD

Attention deficit in schizophrenia may be underestimated due to limited sensitivity of attention tests. Comparing the frequency of attention deficits in schizophrenia to attention deficit hyperactivity disorder (ADHD) may solve this problem, since all subjects with ADHD should demonstrate impaired attention. Twenty-seven subjects with schizophrenia were compared to 74 clinical controls with ADHD on tests of focused/divided/sustained attention and impulsivity. Results: The frequency of impaired attention was equal among subjects with schizophrenia and ADHD-combined (ADHD-C), while ADHD-inattentive (ADHD-I) subjects were more impaired. Half the subjects with schizophrenia had a mild impairment in dual processing. Twenty-one percent showed normal performance on all tests. Fewer subjects with schizophrenia were impulsive/hyperactive, and fewer were impaired in sustained attention compared with the ADHD-C and ADHD-I groups, respectively. Conclusion: Attention tests are not sufficiently sensitive to attention deficits in everyday functioning. Taking this into account, the possibility still remains that a substantial portion of subjects with schizophrenia are not impaired in attention.

Behavioral performance predicts grey matter reductions in the right inferior frontal gyrus in young adults with combined type ADHD

Optimized voxel-based morphometry (VBM) was used in the present study to investigate morphometric differences between young adults with combined type Attention Deficit/Hyperactivity Disorder (ADHD) and a well-matched control group. Investigations examined differences on a between-group whole brain level, as well as how individual differences in behavioral performance predicted grey matter differences. Although a whole brain analysis revealed no significant differences between ADHD and control individuals, ADHD but not control individuals exhibited reduced grey matter volume in the right inferior frontal gyrus (rIFG), predicted by poorer behavioral performance on all three measures. A subsequent region-of-interest approach revealed lower grey matter volume in the rIFG in ADHD compared to control individuals. These results suggest that young adults with ADHD show morphometric differences in inferior prefrontal regions, as compared to controls. These morphometric differences are related to disruptions in performance on behavioral tasks that frequently have been reported to be affected in individuals with ADHD.

Do Low-Effort Learning Strategies Mediate Impaired Memory in ADHD?

As a group, participants with attention-deficit/hyperactivity disorder (ADHD) are impaired in academic performance and learning. This may be due to a mild intellectual impairment, impaired attention, or inability to allocate sufficient effort. If the latter is the case, this should be evident in the learning strategies applied. Four indices of learning strategy, considered to measure degree of effort, were analyzed from 67 participants with ADHD and 67 age-matched normal controls between 9 and 16 years of age. The participants with ADHD were impaired with regard to semantic clustering, retroactive interference, and percentage items reported from the middle section of the list even when controlling for IQ and comorbid conduct or oppositional defiant disorders symptoms. In addition, participants with combined ADHD (ADHD-C) did not display the normal proactive interference effect. The four effort indices explained 39% and 35% of the variance in free recall among participants with inattentive ADHD (ADHD-I) and ADHD-C, respectively. IQ was still significant when the effect of strategy measures were accounted for, whereas diagnosis was no longer significant when entered into the regression analysis after the effort indices. The study shows that participants with ADHD employ less effortful learning strategies than healthy controls and that low effort to a large degree can account for diagnosis related variance in memory performance.

NICE guideline: attention deficit hyperactivity disorder

ADHD (attention deficit hyperactivity disorder) is a heterogeneous behavioural syndrome characterised by maladaptive levels of hyperactivity, impulsivity and inattention. ADHD (as defined by DSM-IV-TR) is a common disorder affecting 3.6%...

Direct and Indirect Measures of Social Perception, Behavior, and Emotional Functioning in Children with Asperger’s Disorder, Nonverbal Learning Disability, or ADHD

Understanding social interactions is crucial for development of social competence. The present study was one of the first to utilize direct and indirect measures of social perception to explore possible differences among children with nonverbal learning disability (NLD), Asperger's Syndrome (AS), Attention Deficit Hyperactivity Disorder-Combined (ADHD-C), Attention Deficit Hyperactivity Disorder-Predominately Inattentive (ADHD-PI), and controls (N = 342). Multiple informants provided ratings of the child's behavioral and social functioning. Results indicated that the NLD and AS groups experienced the most difficulty understanding emotional and nonverbal cues on the direct measure. In addition, children with AS or NLD showed significant signs of sadness and social withdrawal compared to the other groups. Attentional skills, while related to social perception, did not predict social perception difficulties to the same degree as number of AS symptoms.

Attentional Control Activation Relates to Working Memory in Attention-Deficit/Hyperactivity Disorder

Attentional control difficulties in individuals with attention-deficit/hyperactivity disorder (ADHD) might reflect poor working memory (WM) ability, especially because WM ability and attentional control rely on similar brain regions. The current study examined whether WM ability might explain group differences in brain activation between adults with ADHD and normal control subjects during attentional demand. Participants were 20 adults with ADHD combined subtype with no comorbid psychiatric or learning disorders and 23 control subjects similar in age, IQ, and gender. The WM measures were obtained from the Wechsler Adult Intelligence Scale-III and Wechsler Memory Scale-Revised. Brain activation was assessed with functional magnetic resonance imaging (fMRI) while performing a Color-Word Stroop task. Group differences in WM ability explained a portion of the activation in left dorsolateral prefrontal cortex (DLPFC), which has been related to the creation and maintenance of an attentional set for task-relevant information. In addition, greater WM ability predicted increased activation of brain regions related to stimulus-driven attention and response selection processes in the ADHD group but not in the control group. The inability to maintain an appropriate task set in young adults with combined type ADHD, associated with decreased activity in left DLPFC, might in part be due to poor WM ability. Furthermore, in individuals with ADHD, higher WM ability might relate to increased recruitment of stimulus-driven attention and response selection processes, perhaps as a compensatory strategy.

Electrophysiological evidence for abnormal preparatory states and inhibitory processing in adult ADHD

BackgroundAttention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. Several theories postulate deficits in ADHD that have effects across many executive functions or in more narrowly defined aspects, such as response inhibition. Electrophysiological studies on children, however, indicate that ADHD is not associated with a core deficit of response inhibition, as abnormal inhibitory processing is typically preceded or accompanied by other processing deficits. It is not yet known if this pattern of abnormal processing is evident in adult ADHD.MethodsThe objective of this paper was to investigate event-related potential indices of preparatory states and subsequent response inhibition processing in adults with ADHD. Two cued continuous performance tasks were presented to 21 adults meeting current criteria for adult ADHD and combined type ADHD in childhood, and 20 controls.ResultsThe ADHD group exhibited significantly weaker orienting attention to cues, cognitive preparation processes and inhibitory processing. In addition, we observed a strong correlation between the resources allocated to orienting to cues and the strength of the subsequent response strength control processes, suggesting that orienting deficits partly predict and determine response control deficits in ADHD.ConclusionsThese findings closely resemble those previously found in children with ADHD, which indicate that there is not a core response inhibition deficit in ADHD. These findings therefore suggest the possibility of developmental stability into adulthood of the underlying abnormal processes in ADHD.

P01-223 - A Study on the polymorphism of DRD4exoniii48bp VNTR and executive function in Han Chinese children with Tourette's Syndrome

ObjectiveThe relationship of DRD4exonIII48bp VNTR and executive function were studied in 86 children with Tourette's Syndrome.Methods86 Han Chinese children with GTS were tested using a set of neuropsychological test(Stroop test, trail making test,modified Wisconsin Card sorting test) and compared with 51 healthy control group to understand the relationship between executive deficits and genetics.ResultsCompared with normal children, The GTS group showed impairment on almost all psychological measures. In some stroop test, combined ADHD group differed from the GTS-alone group. No evidence show significantly difference among DRD4exonIII48bp VNTR and executive function.ConclusionGTS patient has executive function deficits,these deficits may have nothing to do with DRD4exonIII48bp VNTR.For comorbid, there is a certain influence in the executive function.

Recognition and referral of girls with Attention Deficit Hyperactivity Disorder: case vignette study

Compared with boys, girls with Attention Deficit Hyperactivity Disorder (ADHD) are under-recognized. Parents commonly discuss concerns with teachers, who play an important role in the recognition and referral of children with ADHD. We investigated whether the predominating subtype of symptomatology influences teacher recognition of affected girls. A total of 212 teachers from 40 randomly selected primary schools in England participated in a postal questionnaire study. The questionnaire consisted of a case vignette (based on DSM-IV criteria) describing a girl with either combined or predominantly inattentive subtype ADHD. Each school received an equal number of each type of vignette for distribution. Further questions elicited teachers' conceptualization of the girl's difficulties and need for specialist referral, their views on treatment modalities and demographic data. Most (98%) teachers recognized the presence of a problem but mainly conceptualized the girl's behaviour as reflecting attentional (89%) or emotional (62%) difficulties. Teachers were less likely to correctly identify a girl with inattentive than combined subtype ADHD (14% vs. 43%) or recommend clinical referral (50% vs. 59%) for her. Few (15%) teachers thought that medication might be helpful for a girl meeting diagnostic criteria for ADHD. Teachers are able to recognize ADHD-related behaviours and impairments but conceptualize these as reflecting attentional or emotional difficulties rather than as relating to a disorder (ADHD). Teachers' conceptualization of ADHD and views about medication are important factors that could affect accurate recognition and referral. Improving teachers' knowledge about ADHD, especially the inattentive subtype, could assist in tackling gender-related barriers to care.

Comorbidity in Adults with Attention-Deficit Hyperactivity Disorder

To examine the prevalence of comorbid Axis I (current and lifetime) and II disorders in adult men and women with attention-deficit hyperactivity disorder (ADHD). Adult patients (n = 447; 266 men, 181 women) received comprehensive assessments for ADHD and Axis I and II disorders. Adults were aged between 17 and 74 years. Among the patients diagnosed with ADHD (n = 335), there were those with ADHD inattentive subtype (ADHD-I) (n = 199), hyperactive-impulsive subtype (ADHD-H) (n = 24), or combined ADHD subtype (ADHD-C) (n = 112). Chi-square and logistic regression analyses were performed to examine associations between adults with and without ADHD on Axis I and II disorders. Adults with ADHD, compared with those without ADHD, had higher rates of Axis I (46.9% and 27.31%) and Axis II (50.7% and 38.2%) disorders. Adults with ADHD-C were more likely to have mood disorder, anxiety, conduct disorder, and substance use disorder as well as obsessive-compulsive personality disorder, passive-aggressive personality disorder, depressive personality disorder, narcissistic personality disorder, and borderline personality disorder (BPD). Men with ADHD were more likely to have antisocial personality disorder and had higher rates of current drug abuse than women with ADHD. Women with ADHD had higher rates of past and current panic disorder, and past anorexia and bulimia. Women with ADHD were more likely to have BPD than men with ADHD. Adults with ADHD have very high rates of comorbid Axis I and II disorders, with differences found between men and women on certain comorbid disorders.

Dopamine and serotonin transporter genotypes moderate sensitivity to maternal expressed emotion: the case of conduct and emotional problems in attention deficit/hyperactivity disorder

Mothers' positive emotions expressed about their children with attention deficit/hyperactivity disorder (ADHD) are associated with a reduced likelihood of comorbid conduct problems (CP). We examined whether this association with CP, and one with emotional problems (EMO), is moderated by variants within three genes, previously reported to be associated with ADHD and to moderate the impact of environmental risks on conduct and/or emotional problems; the dopamine transporter gene (SLC6A3/DAT1), the dopamine D4 receptor gene (DRD4) and the serotonin transporter gene (SLC6A4/5HTT). Seven hundred and twenty-eight males between the ages of 5 and 17 with a DSM-IV research diagnosis of combined type ADHD were included in these analyses. Parents and teachers rated children's conduct and emotional problems. Positive maternal expressed emotion (PMEE) was coded by independent observers on comments made during a clinical assessment with the mother based on current or recent medication-free periods. Sensitivity to the effects of PMEE on CP was moderated by variants of the DAT1 and 5HTT genes. Only children who did not carry the DAT1 10R/10R or the 5HTT l/l genotypes showed altered levels of CP when exposed to PMEE. The effect was most marked where the child with ADHD had both these genotypes. For EMO, sensitivity to PMEE was found only with those who carried the DAT1 9R/9R. There was no effect of DRD4 on CP or EMO. The gene-environment interactions observed suggested that genetic make-up can alter the degree of sensitivity an ADHD patients has to their family environment. Further research should focus on distinguishing general sensitivity genotypes from those conferring risk or protective qualities.

Attention Deficit Hyperactivity Disorder: A Rasch Analysis of the SWAN Rating Scale

The prevalence of attention-deficit/hyperactivity disorder (ADHD) has been estimated at 3-7% in the population. Children with this disorder are often characterized by symptoms of inattention and/or impulsivity and hyperactivity, which can significantly impact on many aspects of their behaviour and performance. This study investigated the characteristics of the SWAN Rating Scale and its discrimination of ADHD subtypes. This instrument was developed by Swanson and his colleagues and measures attentiveness and hyperactivity on a continuum, from attention problems to positive attention skills, using a seven-point scale of behaviour: "far below average" to "far above average". The Australian Twin Attention-Deficit/Hyperactivity Disorder Study consists of questionnaire data collected from families in 1990/2007. The Rasch model was used to measure the characteristics of items from the SWAN Rating Scale; how well these items discriminated between those with and without ADHD. The prevalence of each subtype was found to be 5.3% for inattentive ADHD, 4.3% for hyperactive ADHD and 4.6% for combined ADHD. A total of 14.2% of the cohort appeared to have ADHD. While the inattentive items appeared to be consistent with each other in their measurement behaviour and response patterns, the hyperactive items were less consistent. Further, the combined subtype appeared to be an entirely different type, with unique features unlike the other two subtypes. Further work is needed to distinguish the diagnostic features of each subtype of ADHD.

Differentiation between attention‐deficit/hyperactivity disorder and pervasive developmental disorders with hyperactivity on objective activity levels using actigraphs

To clarify differences in objective activity levels between children with attention-deficit/hyperactivity disorder (ADHD) and those with pervasive developmental disorders (PDD) and hyperactivity. Eighteen boys with combined type ADHD, 10 boys with PDD with hyperactivity, and 18 control boys wore actigraphs for 1 week while attending elementary school. In addition to the average activity level, the standard deviation in the activity levels were compared for two continuous situations: (i) in-seat classes, in which the participants were expected to sit in their own seats and learn quietly; and (ii) free recess periods following the in-seat classes. All the groups were affected by the situational shift, the average activity level of each the groups was higher and the standard deviation was smaller than those during the in-seat classes. The boys with ADHD exhibited a still smaller standard deviation than the controls and the boys with PDD and hyperactivity during the free recess period; no difference between the controls and the boys with PDD was seen. The boys with PDD exhibited a significantly lower average activity level than the other groups. No differences among the groups in the average activity levels and standard deviation were seen during the in-seat classes. The observed objective activity levels in each group reflect the degree to which the boys are able to tolerate changes in situations. Objective measurement of activity levels may be useful to differentiate hyperactivity in children with ADHD from that in children without ADHD.

Cognitive versus Behavioral ADHD Phenotype: What is it all About?

The ADHD PASS assessment is discussed. 100 combined and 50 inattentive ADHD patients with DSM IV - TR criteria, no comorbidity, and no previous treatment were enrolled. Those with SNAP-IV> or =2.5/1.8 (teacher/parents) [n=96] were randomly assigned to 1 of 3 treatment groups: Concerta, humanistic psychology, and Concerta+psychology. Those with SNAP-IV<2.5/1.8 [n=54] to 1 of 2 groups: Concerta and Concerta+psychology. All of them [n=150] we administered the SNAP-IV and cognitive DN:CAS battery at baseline and 6 and 12 months later. Cluster analysis and paired Student t-test were applied. The cluster analysis produced three cognitive profiles: one [n=96] with planning dysfunction and SNAP-IV> or =2.5/1.8, the majority [n=76] combined ADHD; another [n=38] with successive processing dysfunction and SNAP-IV<2.5/1.8, the majority [n=28] inattentive ADHD; and another [n=16] without cognitive dysfunction and with SNAP-IV<2.5/1.8, [n=8] combined and [n=8] inattentive. Only planning ameliorated at 12 months assessment. It was better in group 3 (p<0.1) than in group 1 (p<0.5), than in group 2 (p<0.4/0.3). Remission was parallel to planning improvement, group 3>group 1> group 2. PASS assessment in ADHD may be relevant.

Efficacy and safety of atomoxetine as add-on to psychoeducation in the treatment of attention deficit/hyperactivity disorder

The primary objective of this study was to assess the impact of atomoxetine in combination with psychoeducation, compared with placebo and psychoeducation, on health-related quality of life (HRQL) in Swedish stimulant-naïve pediatric patients with attention deficit/hyperactivity disorder (ADHD). HRQL results will be presented elsewhere. Here, psychoeducation as well as efficacy and safety of the treatment are described. A total of 99 pediatric ADHD patients were randomized to a 10-week double-blind treatment with atomoxetine (49 patients) or placebo (50 patients). Parents of all patients received four sessions of psychoeducation. Atomoxetine was dosed up to approximately 1.2 mg/kg day (< or = 70 kg) or 80 mg/day (> 70 kg). Improvement of ADHD symptoms was evaluated using the ADHD rating scale (ADHD-RS) and clinical global impression (CGI) rating scales. Safety was assessed based on adverse events (AEs). The study population was predominantly male (80.8%) and diagnosed with the combined ADHD subtype (77.8%). The least square mean (lsmean) change from baseline to endpoint in total ADHD-RS score was -19.0 for atomoxetine patients and -6.3 for placebo patients, resulting in an effect size (ES) of 1.3 at endpoint. Treatment response (reduction in ADHD-RS score of > or = 25 or > or = 40%) was achieved in 71.4 or 63.3% of atomoxetine patients and 28.6 or 14.3% of placebo patients. The lsmean change from baseline to endpoint in CGI-Severity was -1.8 in the atomoxetine group compared with -0.3 in the placebo group. The difference between treatments in CGI-Improvement at endpoint was -1.4 in favor of atomoxetine. No serious AEs occurred. The safety profile of atomoxetine was in line with the current label. Atomoxetine combined with psychoeducation was superior to placebo and psychoeducation in ADHD core symptoms improvement. The large ES might be a result of including stimulant-naïve patients only, but also may indicate a positive interaction between atomoxetine treatment and psychoeducation, possibly by increased compliance.

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

BackgroundThe 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.Methods25 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.ResultsOn 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.ConclusionThe 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.