Inhibitory deficits in attention-deficit/hyperactivity disorder are independent of basic processing efficiency and IQ

Deviations from a typical development of the cerebellum in youth are associated with psychopathology, executive functions and educational outcomes

BACKGROUND

Understanding deviations from typical brain development is a promising approach to comprehend pathophysiology in childhood and adolescence. We investigated if cerebellar volumes different than expected for age and sex could predict psychopathology, executive functions and academic achievement.

METHODS

Children and adolescents aged 6-17 years from the Brazilian High-Risk Cohort Study for Mental Conditions had their cerebellar volume estimated using Multiple Automatically Generated Templates from T1-weighted images at baseline (n = 677) and at 3-year follow-up (n = 447). Outcomes were assessed using the Child Behavior Checklist and standardized measures of executive functions and school achievement. Models of typically developing cerebellum were based on a subsample not exposed to risk factors and without mental-health conditions (n = 216). Deviations from this model were constructed for the remaining individuals (n = 461) and standardized variation from age and sex trajectory model was used to predict outcomes in cross-sectional, longitudinal and mediation analyses.

RESULTS

Cerebellar volumes higher than expected for age and sex were associated with lower externalizing specific factor and higher executive functions. In a longitudinal analysis, deviations from typical development at baseline predicted inhibitory control at follow-up, and cerebellar deviation changes from baseline to follow-up predicted changes in reading and writing abilities. The association between deviations in cerebellar volume and academic achievement was mediated by inhibitory control.

CONCLUSIONS

Deviations in the cerebellar typical development are associated with outcomes in youth that have long-lasting consequences. This study highlights both the potential of typical developing models and the important role of the cerebellum in mental health, cognition and education.

The efficacy of physical exercise interventions on mental health, cognitive function, and ADHD symptoms in children and adolescents with ADHD: an umbrella review

Background

A considerable number of published reviews have addressed the effects of physical exercise on mental health, cognitive function, or attention-deficit hyperactivity (ADHD) symptoms as outcomes in children and adolescents with ADHD. Their findings have often conflicted, therefore, there is an urgent need to synthesise a hierarchy of the evidence and examine the credibility of previous meta-analyses. To establish the robustness of these findings, we conducted an additional meta-analysis on a number of individual studies that were not covered in previous reviews but were suitable for inclusion in our own study.

Methods

Three reviewers independently searched Web of Science, Psych INFO, Embase, Cochrane Library, PubMed, SPORTDiscus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) for meta-analyses published between database inceptions to December 1, 2022. The individual studies were also screened from 1 January 2015 to 1 December 2022. We included meta-analyses and eligible individual studies that addressed the effects of exercise on at least one outcome of mental health, cognitive function, or ADHD symptoms in children and adolescents with ADHD. We excluded systematic reviews and articles that lacked sufficient data for a meaningful second analysis. The effect estimates (Hedges' g), 95% confidence interval (95% CI), 95% prediction interval (95% PI), small study effects, and excess significance bias were calculated. Finally, we categorised the meta-analyses based on the credibility of the evidence criteria and their quality using a Measurement Tool to Assess Systematic Reviews 2 checklist. This umbrella review was registered with PROSPERO, CRD42022361331.

Findings

Of 181 listed review articles and 60 individual papers, 10 reviews and 12 individual articles were included in the meta-analyses. This yielded 37 meta-analyses based on 106 study estimates. Evidence was highly suggestive for the effectiveness of exercise (class II) for improving inattention (G = 0.92, 95% CI: 0.44-1.39, 95%), inhibitory control (G = 0.82, 95% CI: 0.52-1.13), and cognitive flexibility (G = 0.52, 95% CI: 0.32-0.72). However, evidence for the effectiveness of exercise on emotional, social, and working memory outcomes was weak, and these results were not significant for hyperactivity and behavioural functioning.

Interpretation

Improvement of cognitive flexibility, inhibitory control, and inattention in children and adolescents with ADHD was highly suggested by exercise interventions. However, results were weak for other outcomes (emotional functioning, social functioning, and working memory). Further high-quality randomised controlled trials are, therefore, warranted to determine the effectiveness of exercise on weak outcomes.

Funding

None.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task. The Simon task is a conflict task that is well-adapted to dissociate proactive and reactive inhibition. Beyond classical global measures (mean reaction time, accuracy rate, and interference effect), we used more sophisticated dynamic analyses of the interference effect and accuracy rate to investigate reactive inhibition. We studied proactive inhibition through the congruency sequence effect (CSE).Our results showed that children with ADHD had impaired reactive but not proactive inhibition. Moreover, the deficit found in reactive inhibition seems to be due to both a stronger impulse capture and more difficulties in inhibiting impulsive responses. These findings contribute to a better understanding of how ADHD affects inhibitory control in children.

Testing the Stability and Validity of an Executive Dysfunction Classification Using Task-Based Assessment in Children and Adolescents

OBJECTIVE

It is unclear if pediatric executive dysfunction assessed only with cognitive tasks predicts clinically relevant outcomes independently of psychiatric diagnoses. This study tested the stability and validity of a task-based classification of executive function.

METHOD

A total of 2,207 individuals (6-17 years old) from the Brazilian High-Risk Cohort Study participated in this study (1,930 at baseline, 1,532 at follow-up). Executive function was measured using tests of working memory and inhibitory control. Dichotomized age- and sex-standardized performances were used as input in latent class analysis and receiver operating curves to create an executive dysfunction classification (EDC). The study tested EDC's stability over time, association with symptoms, functional impairment, a polymorphism in the CADM2 gene, polygenic risk scores (PRS), and brain structure. Analyses covaried for age, sex, social class, IQ, and psychiatric diagnoses.

RESULTS

EDC at baseline predicted itself at follow-up (odds ratio [OR] = 5.11; 95% CI 3.41-7.64). Participants in the EDC reported symptoms spanning several domains of psychopathology and exhibited impairment in multiple settings, including more adverse school events (OR = 2.530; 95% CI 1.838-3.483). Children in the EDC presented higher attention-deficit/hyperactivity disorder and lower educational attainment PRS at baseline; higher schizophrenia PRS at follow-up; and lower chances of presenting a polymorphism in a gene previously linked to high performance in executive function (CADM2 gene). They also exhibited smaller intracranial volumes and smaller bilateral cortical surface areas in several brain regions.

CONCLUSION

Task-based executive dysfunction is associated with several validators, independently of psychiatric diagnoses and intelligence. Further refinement of task-based assessments might generate clinically useful tools.

Neuroimaging Association Scores: reliability and validity of aggregate measures of brain structural features linked to mental disorders in youth

In genetics, aggregation of many loci with small effect sizes into a single score improved prediction. Nevertheless, studies applying easily replicable weighted scores to neuroimaging data are lacking. Our aim was to assess the reliability and validity of the Neuroimaging Association Score (NAS), which combines information from structural brain features previously linked to mental disorders. Participants were 726 youth (aged 6-14) from two cities in Brazil who underwent MRI and psychopathology assessment at baseline and 387 at 3-year follow-up. Results were replicated in two samples: IMAGEN (n = 1627) and the Healthy Brain Network (n = 843). NAS were derived by summing the product of each standardized brain feature by the effect size of the association of that brain feature with seven psychiatric disorders documented by previous meta-analyses. NAS were calculated for surface area, cortical thickness and subcortical volumes using T1-weighted scans. NAS reliability, temporal stability and psychopathology and cognition prediction were analyzed. NAS for surface area showed high internal consistency and 3-year stability and predicted general psychopathology and cognition with higher replicability than specific symptomatic domains for all samples. They also predicted general psychopathology with higher replicability than single structures alone, accounting for 1-3% of the variance, but without directionality. The NAS for cortical thickness and subcortical volumes showed lower internal consistency and less replicable associations with behavioural phenotypes. These findings indicate the NAS based on surface area might be replicable markers of general psychopathology, but these links are unlikely to be causal or clinically useful yet.

Genetic risk for Alzheimer's disease and functional brain connectivity in children and adolescents

Research suggested accumulation of tau proteins might lead to the degeneration of functional networks. Studies investigating the impact of genetic risk for Alzheimer's disease (AD) on early brain connections might shed light on mechanisms leading to AD development later in life. Here, we aim to investigate whether the polygenic risk score for Alzheimer's disease (AD-PRS) influences the connectivity among regions susceptible to tau pathology during childhood and adolescence. Participants were youth, aged 6-14 years, and recruited in Porto Alegre (discovery sample, n = 332) and São Paulo (replication sample, n = 304), Brazil. Subjects underwent genotyping and 6-min resting state funcional magnetic resonance imaging. Connections between the local maxima of tau pathology networks were used as dependent variables. The AD-PRS was associated with the connectivity between the right precuneus and the right superior temporal gyrus (discovery sample: β = 0.180, p_adjusted = 0.036; replication sample: β = 0.202, p = 0.031). This connectivity was also associated with inhibitory control (β = 0.157, p_adjusted = 0.035) and moderated the association between the AD-PRS and both immediate and delayed recall. These findings suggest the AD-PRS may affect brain connectivity in youth, which might impact memory performance and inhibitory control in early life.

Heterotypic trajectories of dimensional psychopathology across the lifespan: the case of youth-onset attention deficit/hyperactivity disorder

BACKGROUND

Recent studies have demonstrated the existence of a distinct late-onset attention deficit/hyperactivity disorder (ADHD) trajectory. Our objective is to test if there are distinct ADHD trajectories regarding age of onset from childhood to adolescence and to compare clinical manifestations, cognitive functions and genetic risk for ADHD among distinct longitudinal groups.

METHOD

Nine hundred and twenty four children and adolescents from the community participated in the study. We compared clinical, cognitive features and genetic risk among four groups of participants: (a) childhood-limited, (b) youth-onset, (c) childhood-onset with youth persistence, and (d) community comparisons without ADHD. Symptomatic and diagnostic assessments were performed using the Development and Well-Being Behavior Assessment, the Strengths and Difficulties Questionnaire, and the Child Behavior Checklist. Cognitive functions were measured using a battery of standardized tests. Genetic risk for ADHD was calculating using summary statistics from the Psychiatric Genomics Consortium.

RESULTS

Half of the adolescents (52%) with ADHD had their symptom onset in adolescence. The impairment level of this group in adolescence is similar to the persistent group. Despite not having ADHD, the youth-onset group already presented in childhood more symptoms from other domains of psychopathology, higher shared variance in psychiatric symptomatology (p-factor), school impairment, and executive dysfunctions than community comparisons. Furthermore, the youth-onset group presented lower levels of genetic risk for ADHD compared to other cases.

CONCLUSIONS

A significant proportion of adolescents with ADHD were youth-onset cases and presented similar impairment levels as those cases with early-onset ADHD. The presence of cognitive impairments and higher levels of clinical symptoms in the youth-onset group already at childhood speaks in favor of a heterotypic trajectory of psychopathology suggesting that youth-onset ADHD might be an artificial consequence of categorizing dimensional psychopathology into discrete diagnostic groups.

Hot and cool executive function in children and adolescents with autism spectrum disorder: Cross-sectional developmental trajectories

The development of executive function (EF) in autism spectrum disorder (ASD) has only been investigated using "cool"-cognitive-EF tasks. Little is known about the development of "hot"-affective-EF and whether it follows a similar developmental pathway. This study employed a cross-sectional developmental trajectories approach to examine the developmental changes in cool (working memory, inhibition, and planning) and hot EF (delay discounting and affective decision-making) of ASD participants (n = 79) and controls (n = 91) relative to age and IQ, shedding more light on the hot-cool EF organization. The developmental trajectories of some aspects of cool EF (working memory and planning) differed significantly as a function of age in ASD participants relative to controls. For both hot EFs, no significant age-related changes were found in either group. These findings extend our understanding regarding the maturation of EF from childhood through adolescence in ASD.

The relationship between the development of response inhibition and intelligence in preschool children

Building on the theoretical framework that intellectual behavior relies on one's ability to process both task-relevant and task-irrelevant information, this study aimed to empirically investigate the association of response inhibition with intelligence in preschool children's development. In a sample of 152 typically developing children aged between 3.6 and 6.6 years, we found evidence that suggests that inhibitory control is linked to age-related differences in intelligence. Stop-signal inhibition improved at a rate similar to the age-related changes in Verbal IQ. Components of variance analyses revealed that stop-signal reaction time predicted a larger proportion of the age-related variance in children's verbal intelligence than non-age-related variance. Results are discussed with respect to possible explanations for this intriguing relationship between response inhibition and the verbal aspects of intelligence.

High risk cohort study for psychiatric disorders in childhood: rationale, design, methods and preliminary results

The objective of this study is to present the rationale, methods, design and preliminary results from the High Risk Cohort Study for the Development of Childhood Psychiatric Disorders. We describe the sample selection and the components of each phases of the study, its instruments, tasks and procedures. Preliminary results are limited to the baseline phase and encompass: (i) the efficacy of the oversampling procedure used to increase the frequency of both child and family psychopathology; (ii) interrater reliability and (iii) the role of differential participation rate. A total of 9937 children from 57 schools participated in the screening procedures. From those 2512 (random = 958; high risk = 1554) were further evaluated with diagnostic instruments. The prevalence of any child mental disorder in the random strata and high-risk strata was 19.9% and 29.7%. The oversampling procedure was successful in selecting a sample with higher family rates of any mental disorders according to diagnostic instruments. Interrater reliability (kappa) for the main diagnostic instrument range from 0.72 (hyperkinetic disorders) to 0.84 (emotional disorders). The screening instrument was successful in selecting a sub-sample with "high risk" for developing mental disorders. This study may help advance the field of child psychiatry and ultimately provide useful clinical information.

Different effects of adding white noise on cognitive performance of sub-, normal and super-attentive school children

OBJECTIVES

Noise often has detrimental effects on performance. However, because of the phenomenon of stochastic resonance (SR), auditory white noise (WN) can alter the "signal to noise" ratio and improve performance. The Moderate Brain Arousal (MBA) model postulates different levels of internal "neural noise" in individuals with different attentional capacities. This in turn determines the particular WN level most beneficial in each individual case-with one level of WN facilitating poor attenders but hindering super-attentive children. The objective of the present study is to find out if added WN affects cognitive performance differently in children that differ in attention ability.

METHODS

Participants were teacher-rated super- (N = 25); normal- (N = 29) and sub-attentive (N = 36) children (aged 8 to 10 years). Two non-executive function (EF) tasks (a verbal episodic recall task and a delayed verbal recognition task) and two EF tasks (a visuo-spatial working memory test and a Go-NoGo task) were performed under three WN levels. The non-WN condition was only used to control for potential differences in background noise in the group testing situations.

RESULTS

There were different effects of WN on performance in the three groups-adding moderate WN worsened the performance of super-attentive children for both task types and improved EF performance in sub-attentive children. The normal-attentive children's performance was unaffected by WN exposure. The shift from moderate to high levels of WN had little further effect on performance in any group.

SIGNIFICANCE

The predicted differential effect of WN on performance was confirmed. However, the failure to find evidence for an inverted U function challenges current theories. Alternative explanations are discussed. We propose that WN therapy should be further investigated as a possible non-pharmacological treatment for inattention.

Mechanisms underpinning inattention and hyperactivity: neurocognitive support for ADHD dimensionality

BACKGROUND

Taxometric and behavioral genetic studies suggest that attention deficit hyperactivity disorder (ADHD) is best modeled as a dimension rather than a category. We extended these analyses by testing for the existence of putative ADHD-related deficits in basic information processing (BIP) and inhibitory-based executive function (IB-EF) in individuals in the subclinical and full clinical ranges. Consistent with the dimensional model, we predicted that ADHD-related deficits would be expressed across the full spectrum, with the degree of deficit linearly related to the severity of the clinical presentation.

METHOD

A total of 1547 children (aged 6-12 years) participated in the study. The Development and Well-Being Assessment (DAWBA) was used to classify children into groups according to levels of inattention and hyperactivity independently: (1) asymptomatic, (2) subthreshold minimal, (3) subthreshold moderate and (4) clinical ADHD. Neurocognitive performance was evaluated using a two-choice reaction time task (2C-RT) and a conflict control task (CCT). BIP and IB-EF measures were derived using a diffusion model (DM) for decomposition of reaction time (RT) and error data.

RESULTS

Deficient BIP was found in subjects with minimal, moderate and full ADHD defined in terms of inattention (in both tasks) and hyperactivity/impulsivity dimensions (in the 2C-RT). The size of the deficit increased in a linear manner across increasingly severe presentations of ADHD. IB-EF was unrelated to ADHD.

CONCLUSIONS

Deficits in BIP operate at subclinical and clinical levels of ADHD. The linear nature of this relationship provides support for a dimensional model of ADHD in which diagnostic thresholds are defined in terms of clinical and societal burden rather than representing discrete pathophysiological states.

Specificity of basic information processing and inhibitory control in attention deficit hyperactivity disorder

BACKGROUND

Both inhibitory-based executive functioning (IB-EF) and basic information processing (BIP) deficits are found in clinic-referred attention deficit hyperactivity disorder (ADHD) samples. However, it remains to be determined whether: (1) such deficits occur in non-referred samples of ADHD; (2) they are specific to ADHD; (3) the co-morbidity between ADHD and oppositional defiant disorder/conduct disorder (ODD/CD) has additive or interactive effects; and (4) IB-EF deficits are primary in ADHD or are due to BIP deficits.

METHOD

We assessed 704 subjects (age 6-12 years) from a non-referred sample using the Development and Well-Being Assessment (DAWBA) and classified them into five groups: typical developing controls (TDC; n = 378), Fear disorders (n = 90), Distress disorders (n = 57), ADHD (n = 100), ODD/CD (n = 40) and ADHD+ODD/CD (n = 39). We evaluated neurocognitive performance with a Two-Choice Reaction Time Task (2C-RT), a Conflict Control Task (CCT) and a Go/No-Go (GNG) task. We used a diffusion model (DM) to decompose BIP into processing efficiency, speed-accuracy trade-off and encoding/motor function along with variability parameters.

RESULTS

Poorer processing efficiency was found to be specific to ADHD. Faster encoding/motor function differentiated ADHD from TDC and from fear/distress whereas a more cautious (not impulsive) response style differentiated ADHD from both TDC and ODD/CD. The co-morbidity between ADHD and ODD/CD reflected only additive effects. All ADHD-related IB-EF classical effects were fully moderated by deficits in BIP.

CONCLUSIONS

Our findings challenge the IB-EF hypothesis for ADHD and underscore the importance of processing efficiency as the key specific mechanism for ADHD pathophysiology.

Developments and challenges in the diagnosis and treatment of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder, often associated with other psychiatric comorbidities, functional impairments, and poor long-term outcomes. The objective of this selected review is to describe current advances and challenges in the diagnosis and treatment of ADHD. The disorder is associated with neurobiological underpinnings and is highly heterogeneous in various aspects, such as symptom profiles, cognitive impairments, and neurobiological and genetic features. The efficacy and safety of short-term pharmacological treatments across the life cycle is well studied, but further research investigating long-term treatment, impact of treatment in preschoolers, and non-pharmacological interventions is needed. Future research is also needed to better characterize the neurodevelopmental pathways of the disorder, linking clinical and neurobiological information, less investigated populations, and new interventions.

Multiple behavioural impulsivity tasks predict prospective alcohol involvement in adolescents

AIMS

We investigated reciprocal prospective relationships between multiple behavioural impulsivity tasks (assessing delay discounting, risk-taking and disinhibition) and alcohol involvement (consumption, drunkenness and problems) among adolescents. We hypothesized that performance on the tasks would predict subsequent alcohol involvement, and that alcohol involvement would lead to increases in behavioural impulsivity over time.

DESIGN

Cross-lagged prospective design in which impulsivity and alcohol involvement were assessed five times over 2 years (once every 6 months, on average).

SETTING

Classrooms in secondary schools in North West England.

PARTICIPANTS

Two hundred and eighty-seven adolescents (51.2% male) who were aged 12 or 13 years at study enrolment.

MEASUREMENTS

Participants reported their alcohol involvement and completed computerized tasks of disinhibition, delay discounting and risk-taking at each assessment. Cross-sectional and prospective relationships between the variables of interest were investigated using cross-lagged analyses.

FINDINGS

All behavioural impulsivity tasks predicted a composite index of alcohol involvement 6 months later (all Ps < 0.01), and these prospective relationships were reliable across the majority of time-points. Importantly, we did not observe the converse relationship across time: alcohol involvement did not predict performance on behavioural impulsivity tasks at any subsequent time point.

CONCLUSIONS

Several measures of impulsivity predict escalation in alcohol involvement in young adolescents, but alcohol use does not appear to alter impulsivity.

Do different ADHD-related etiological risks involve specific neuropsychological pathways? An analysis of mediation processes by inhibitory control and delay aversion

BACKGROUND

Inhibitory control (IC) has been regarded as a neuropsychological basic deficit and as an endophenotype of attention deficit/hyperactivity disorder (ADHD). Implicated here are mediation processes between etiological factors and ADHD symptoms. We thus analyze whether and to what extent executive IC and delay aversion (DA; i.e., reward-related IC) performance mediate the associations of familial, prenatal, and psychosocial risks with ADHD symptoms.

METHODS

The study sample consisted of 130 preschool children (3-6 years; 50% boys), including 20% (n = 26) with a positive family history of ADHD (familial risk). Prenatal risks were mainly taken from medical records. Psychosocial risks were assessed by a structured interview. ADHD symptoms were assessed by structured interviews and questionnaires completed by parents and teachers. A set of neuropsychological tasks on IC and DA was conducted with the children.

RESULTS

Familial, prenatal, and psychosocial risks were significantly associated with ADHD symptoms. IC and DA also correlated significantly with ADHD symptoms. While the familial risk significantly correlated with IC and DA, psychosocial and prenatal risks were only weakly associated with these measures. The link between the familial risk and ADHD symptoms was partially mediated by IC and DA.

CONCLUSIONS

The results indicate different neuropsychological pathways related to 'positive family history of ADHD' and prenatal risks. Given a cross-validation in future studies, the results underscore the endophenotypic character of IC and DA in preschool ages.

Neurocognitive effects of methylphenidate on ADHD children with different DAT genotypes: a longitudinal open label trial

The variable number of tandem repeat polymorphism in the 3'-untranslated region of the dopamine transporter gene (DAT) may influence the variability of the therapeutic response to methylphenidate (MPH) in Attention Deficit/Hyperactivity Disorder (ADHD). For this reason we evaluated the neuropsychological functioning after a prolonged period of MPH treatment and after a specific time from MPH suspension. Relationship between DAT VNTR genotypes and neurocognitive response to MPH was analyzed in a sample of 108 drug-naive ADHD patients. The performance of children with ADHD on measures of working memory, inhibition and planning was assessed at 4, 8 and 24 weeks and at 8 weeks after MPH withdrawal. Patients with 9/9 genotype evidenced an improvement in response inhibition and working memory only at 4 weeks of treatment, in planning at 24 weeks of therapy and after 8 weeks of MPH suspension. Patients with 9/10 showed an improvement in response inhibition at 4, 8 and 24 weeks of treatment, in planning at 24 weeks and after 8 weeks of MPH suspension. Patients with 10/10 evidenced an improvement in response inhibition and working memory at 4, 8 and 24 weeks of treatment and in planning at 4, 8 and 24 weeks of treatment and after 8 weeks of suspension. These results indicate that the 9/9 ADHD genotype has a different response at 24 weeks treatment with MPH. 10/10 DAT allele seems to be associated with an increased expression level of the dopamine transporter and seems to mediate the MPH treatment response in ADHD patients.

A meta-analytic study of event rate effects on Go/No-Go performance in attention-deficit/hyperactivity disorder

BACKGROUND

According to the state regulation deficit model, event rate (ER) is an important determinant of performance of children with attention-deficit/hyperactivity disorder (ADHD). Fast ER is predicted to create overactivation and produce errors of commission, whereas slow ER is thought to create underactivation marked by slow and variable reaction times (RT) and errors of omission.

METHODS

To test these predictions, we conducted a systematic search of the literature to identify all reports of comparisons of ADHD and control individuals' performance on Go/No-Go tasks published between 2000 and 2011. In one analysis, we included all trials with at least two event rates and calculated the difference between ER conditions. In a second analysis, we used metaregression to test for the moderating role of ER on ADHD versus control differences seen across Go/No-Go studies.

RESULTS

There was a significant and disproportionate slowing of reaction time in ADHD relative to controls on trials with slow event rates in both meta-analyses. For commission errors, the effect sizes were larger on trials with fast event rates. No ER effects were seen for RT variability. There were also general effects of ADHD on performance for all variables that persisted after effects of ER were taken into account.

CONCLUSIONS

The results provide support for the state regulation deficit model of ADHD by showing the differential effects of fast and slow ER. The lack of an effect of ER on RT variability suggests that this behavioral characteristic may not be a marker of cognitive energetic effects in ADHD.

The effects of priming restrained versus disinhibited behaviour on alcohol-seeking in social drinkers

BACKGROUND

Deficient response inhibition (disinhibition) may play a causal role in alcohol abuse, with impaired inhibition occurring prior to, and acting as a risk factor for, subsequent alcohol problems. We experimentally primed either disinhibited or restrained behaviour while participants completed a Stop-Signal task, before examining the effects on alcohol-seeking behaviour.

METHODS

Fifty three social drinkers completed a Stop-Signal task following instructions that either emphasised rapid responding at the expense of successful inhibition (Disinhibition group) or vice versa (Restrained group). Subsequent ad lib alcohol-seeking was measured with a bogus taste test.

RESULTS

As predicted, participants in the Disinhibition group consumed more beer during the taste test compared to participants in the Restrained group. Furthermore, within the Restrained group only, correlations indicated that those participants who responded more cautiously during the Stop-Signal task subsequently consumed less beer.

CONCLUSIONS

An experimental manipulation of response set during a response inhibition task, emphasising either restrained or disinhibited responding, has a causal influence on alcohol-seeking behaviour in social drinkers.

Executive function profile of Chinese boys with attention-deficit hyperactivity disorder: different subtypes and comorbidity

This study examined the executive function (EF) profile of Chinese boys with attention-deficit hyperactivity disorder (ADHD) using a large sample. Executive function performance within the ADHD subtypes and the effects of comorbidity were also investigated. Five hundred Chinese boys (375 with ADHD and 125 controls) aged 6-15 completed a battery of EF tests. Boys with all types of ADHD performed worse in all of the EF tests than age- and intelligence quotient-matched healthy controls. The boys with the inattention ADHD subtype and the combined subtype showed similar impairments across different EF tasks, whereas the boys with the hyperactive-impulsive ADHD subtype primarily displayed deficits in theory of mind and visual memory. Comorbid oppositional defiant disorder/conduct disorder had no additional influence on the EF characteristics of the boys with ADHD only, whereas comorbid learning disorder increased the severity of inhibition and shifting impairments.

Inhibitory control and psychopathology: a meta-analysis of studies using the stop signal task

The Stop Signal Task (SST) is a measure that has been used widely to assess response inhibition. We conducted a meta-analysis of studies that examined SST performance in patients with various psychiatric disorders to determine the magnitude and generality of deficient inhibition. A five-item instrument was used to assess the methodological quality of studies. We found medium deficits in stop signal reaction time (SSRT), reflecting the speed of the inhibitory process, for attention-deficit hyperactivity disorder (ADHD) (g = 0.62), obsessive compulsive disorder (OCD) (g = 0.77) and schizophrenia (SCZ) (g = 0.69). SSRT was less impaired or normal for anxiety disorder (ANX), autism, major depressive disorder (MDD), oppositional defiant disorder/conduct disorder (ODD/CD), pathological gambling, reading disability (RD), substance dependence, and Tourette syndrome. We observed a large SSRT deficit for comorbid ADHD + RD (g = 0.82). SSRT was less than moderately impaired for ADHD + ANX and ADHD + ODD/CD. Study quality did not significantly affect SSRT across ADHD studies. This confirms an inhibition deficit in ADHD, and suggests that comorbid ADHD has different effects on inhibition in patients with ANX, ODD/CD, and RD. Further studies are needed to firmly establish an inhibition deficit in OCD and SCZ.

Independent contributions of cognitive functioning and social risk factors to symptoms of ADHD in two nordic populations-based cohorts

This study examined independent contributions of executive functioning (EF), state regulation (SR), and social risk factors to symptom dimensions of attention deficit hyperactivity disorder (ADHD) in two cohorts, which included 221 Norwegian children and 294 Finnish adolescents. Independent contributions of EF and SR were shown in the Norwegian cohort and EF contributed independently in the Finnish cohort. When controlling for each symptom dimension, cognitive functioning and social risk factors were differentially associated with inattention and hyperactivity/impulsivity symptoms. The results show the need to include both social risk factors and cognitive functioning to obtain a better understanding of ADHD symptoms.

Beyond the dual pathway model: evidence for the dissociation of timing, inhibitory, and delay-related impairments in attention-deficit/hyperactivity disorder

OBJECTIVE

The dual pathway model explains neuro-psychological heterogeneity in Attention Deficit/Hyperactivity Disorder (ADHD) in terms of dissociable cognitive and motivational deficits each affecting some but not other patients. We explore whether deficits in temporal processing might constitute a third dissociable neuropsychological component of ADHD.

METHOD

Nine tasks designed to tap three domains (inhibitory control, delay aversion and temporal processing) were administered to ADHD probands (n=71; ages 6 to 17 years), their siblings (n=71; 65 unaffected by ADHD) and a group of non-ADHD controls (n=50). IQ and working memory were measured.

RESULTS

Temporal processing, inhibitory control and delay-related deficits represented independent neuropsychological components. ADHD children differed from controls on all factors. For ADHD patients, the co-occurrence of inhibitory, temporal processing and delay-related deficits was no greater than expected by chance with substantial groups of patients showing only one problem. Domain-specific patterns of familial co-segregation provided evidence for the validity of neuropsychological subgroupings.

CONCLUSION

The current results illustrate the neuropsychological heterogeneity in ADHD and initial support for a triple pathway model. The findings need to be replicated in larger samples.

Wavelet-synchronization methodology: a new approach for EEG-based diagnosis of ADHD

A multi-paradigm methodology is presented for electroencephalogram (EEG) based diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD) through adroit integration of nonlinear science; wavelets, a signal processing technique; and neural networks, a pattern recognition technique. The selected nonlinear features are generalized synchronizations known as synchronization likelihoods (SL), both among all electrodes and among electrode pairs. The methodology consists of three parts: first detecting the more synchronized loci (group 1) and loci with more discriminative deficit connections (group 2). Using SLs among all electrodes, discriminative SLs in certain sub-bands are extracted. In part two, SLs are computed, not among all electrodes, but between loci of group 1 and loci of group 2 in all sub-bands and the band-limited EEG. This part leads to more accurate detection of deficit connections, and not just deficit areas, but more discriminative SLs in sub-bands with finer resolutions. In part three, a classification technique, radial basis function neural network, is used to distinguish ADHD from normal subjects. The methodology was applied to EEG data obtained from 47 ADHD and 7 control individuals with eyes closed. The Radial Basis Function (RBF) neural network classifier yielded a high accuracy of 95.6% for diagnosis of the ADHD in the feature space discovered in this research with a variance of 0.7%.

Task complexity enhances response inhibition deficits in childhood and adolescent attention-deficit/hyperactivity disorder: a meta-regression analysis

BACKGROUND

The ability to inhibit motor responses, as assessed by the stop-signal reaction time (SSRT), is impaired in children and adolescents with attention-deficit/hyperactivity disorder (ADHD). However, the between-study variation in effect sizes is large. The aim of this study was to investigate whether this variability can be explained by between-study variation in Go task complexity.

METHOD

Forty-one studies comparing children or adolescents diagnosed with ADHD to normal control subjects were incorporated in a random-effects meta-regression analysis. The independent variables were a global index of Go task complexity (i.e., mean reaction time in control subjects [RTc]) and a more specific index (i.e., spatial compatibility of the stimulus-response mapping). The dependent variable was the SSRT difference between ADHD and control subjects.

RESULTS

The SSRT difference increased significantly with increasing RTc. Moreover, the SSRT difference was significantly increased in studies that employed a noncompatible, that is, arbitrary, mapping compared with studies that incorporated a spatially compatible stimulus-response mapping.

CONCLUSIONS

These results indicate that inhibitory dysfunction in children and adolescents with ADHD varies with task complexity: inhibitory dysfunction in ADHD is most pronounced for spatially noncompatible responses. Explanations in terms of inhibition and working memory deficits and a tentative neurobiological explanation are briefly discussed.

Neuropsychological deficits in relation to symptoms of ADHD: independent contributions and interactions

The aim of the present study was to investigate possible independent and combined effects of inhibitory control, delay aversion, and RT variability in relation to symptoms of hyperactivity/impulsivity and inattention. A community-based sample of school children (N = 111) completed neuropsychological tasks designed to measure inhibitory control, delay aversion, and RT variability. Behavioral symptoms were measured through parental and teacher ratings of the DSM-IV criteria for ADHD and ODD. The results showed that inhibitory control and RT variability were primarily related to symptoms of inattention rather than hyperactivity/impulsivity. Further, out of the three neuropsychological factors studied, only inhibitory control contributed uniquely to the variance of ADHD symptoms. However, significant interaction effects of delay aversion and RT variability on symptoms of both hyperactivity/impulsivity and inattention were found. This study shows the importance of searching for possible combined effects of neuropsychological factors to learn more about the different pathways that lead to ADHD symptoms in children.

Delay Aversion in Attention Deficit/Hyperactivity Disorder: an empirical investigation of the broader phenotype

BACKGROUND

Delay-related motivational processes are impaired in children with Attention Deficit/Hyperactivity Disorder (ADHD). Here we explore the impact of ADHD on the performance of three putative indices of Delay Aversion (DAv): (i) the choice for immediate over delayed reward; (ii) slower reaction times following delay; and (iii) increased delay-related frustration-to see whether these tap into a common DAv construct that differentiates ADHD cases from controls and shows evidence of familiality.

METHOD

Seventy seven male and female individuals (age range 6-17) with a research diagnosis combined type ADHD, 65 of their siblings unaffected by ADHD and 50 non-ADHD controls completed three delay tasks.

RESULTS

As predicted the size of the correlation between tasks was small but a common latent component was apparent. Children with ADHD differed from controls on all tasks (d=.4-.7) and on an overall DAv index (d=.9): The battery as a whole demonstrated moderate sensitivity and specificity. In general, deficits were equally marked in childhood and adolescence and were independent of comorbid ODD. IQ moderated the effect on the MIDA. Scores on the DAv factor co-segregated within ADHD families.

DISCUSSION

There is value in exploring the broader DAv phenotype in ADHD. The results illustrate the power of multivariate approaches to endophenotypes. By highlighting the significant, but limited, role of DAv in ADHD these results are consistent with recent accounts that emphasize neuropsychological heterogeneity.

Inattentive/overactive children with histories of profound institutional deprivation compared with standard ADHD cases: a brief report

BACKGROUND

The Inattention/Overactivity/Impulsiveness (I/OA) behavioural cluster diagnostic of ADHD is recognized as a characteristic outcome of early institutional care.

METHODS

We compared the symptom and neuropsychological profiles of children with a history of I/OA and early severe deprivation (D-I/OA: n=13) with standard clinical ADHD cases (S-ADHD; N=20) and children who had experienced deprivation but were not pervasively I/OA (ERA-controls; n=22). The mean age of testing was around 13 years. D-I/OA and ERA-controls were selected from the English and Romanian Adoptees (ERA) study and had spent their early lives in the extremely depriving Romanian institutions of the Ceausescu regime and were later adopted into UK families.

RESULTS

ADHD symptoms for male D-I/OA and S-ADHD cases showed marked similarities across symptom domains. In contrast, girls with D-I/OA were more similar to ERA controls than to ADHD cases. Longitudinal data suggested that this was due to a remission of symptoms in D-I/OA girls. Neuropsychological profiles of males and females with D-I/OA, however, were similar: both were more impaired than S-ADHD and ERA controls.

DISCUSSION

Children with D-I/OA were more neuropsychologically impaired than S-ADHD despite the fact that only boys showed a persistent pattern of ADHD symptoms. These results need replication in a larger sample with groups matched for gender.