Psychological theories of hyperactivity: a behaviour genetic approach

This study was an attempt to combine two research literatures on hyperactivity: the behaviour genetic research and the studies testing psychological theories of hyperactivity. We obtained behavioural ratings from the teachers of 1316 twin pairs, aged 7-12, from the general population. For a subsample of 268 twin pairs we obtained ratings also from their parents. Forty-six hyperactive twin pairs (pairs in which at least one twin was pervasively hyperactive) and 47 control twin pairs were then assessed on tests relating to three theories of hyperactivity, those of response inhibition deficit, working memory impairment and delay aversion. Confirming previous findings, genetic factors accounted for 50-70% of the variance in hyperactivity when considered as a continuous dimension. There was also significant evidence of genetic effects on extreme hyperactivity, although the present group heritability estimates were somewhat lower than previous estimates. The hyperactive group performed worse than the control group on the delay aversion measure and some of the working memory tasks. Controlling for IQ removed the significant group differences on the working memory measures, however. Although there were no significant group differences on the inhibition variables, the inhibition measure, stop task, produced evidence of a pattern of responding that was strongly characteristic of hyperactivity: hyperactive children were variable in their speed, generally slow and inaccurate. This pattern of responding may indicate a non-optimal effort/activation state. To investigate the possibility that the cognitive impairments or task engagement factors associated with hyperactivity mediate the genetic effects on the condition, bivariate group heritability analyses were carried out. There was significant evidence of shared genetic effects only on extreme hyperactivity and the variability of speed. The findings are interpreted as supporting the state regulation theory of hyperactivity. Although delay aversion is a characteristic of hyperactivity, it seems to have an environmental rather than a genetic origin

Hyperactive-Impulsive Symptom Scores and Oppositional Behaviours Reflect Alternate Manifestations of a Single Liability

Attention deficit hyperactivity disorder (ADHD) and oppositional behaviours frequently co-occur, We aimed to study the etiology of this overlap in a general population–based twin sample, assessing the symptom domains of hyperactivity-impulsivity and inattentiveness separately for their overlap with oppositionality. We further aimed to investigate whether rater bias may contribute to the overlap in previous data which used one rater only. Using parent and teacher ratings on hyperactivity-impulsivity, inattentiveness and oppositionality, and actigraph measurements of activity level, for 668 7-9-year-old twin pairs, oppositionality showed a higher overlap with hyperactivity-impulsivity (r=.95) than with inattentiveness (r=.52) and all etiological influences on hyperactivity-impulsivity were shared with those on oppositionality, indicated by a genetic correlation of .95 and a child-specific environmental correlation of .94. Actigraph data did not show an overlap with ratings of oppositionality. In middle childhood, symptoms of hyperactivity-impulsivity and oppositional behaviour may represent the same underlying liability, whereas the inattentive domain is more distinct

The IMAGE project: methodological issues for the molecular genetic analysis of ADHD

The genetic mechanisms involved in attention deficit hyperactivity disorder (ADHD) are being studied with considerable success by several centres worldwide. These studies confirm prior hypotheses about the role of genetic variation within genes involved in the regulation of dopamine, norepinephrine and serotonin neurotransmission in susceptibility to ADHD. Despite the importance of these findings, uncertainties remain due to the very small effects sizes that are observed. We discuss possible reasons for why the true strength of the associations may have been underestimated in research to date, considering the effects of linkage disequilibrium, allelic heterogeneity, population differences and gene by environment interactions. With the identification of genes associated with ADHD, the goal of ADHD genetics is now shifting from gene discovery towards gene functionality – the study of intermediate phenotypes ('endophenotypes'). We discuss methodological issues relating to quantitative genetic data from twin and family studies on candidate endophenotypes and how such data can inform attempts to link molecular genetic data to cognitive, affective and motivational processes in ADHD. The International Multi-centre ADHD Gene (IMAGE) project exemplifies current collaborative research efforts on the genetics of ADHD. This European multi-site project is well placed to take advantage of the resources that are emerging following the sequencing of the human genome and the development of international resources for whole genome association analysis. As a result of IMAGE and other molecular genetic investigations of ADHD, we envisage a rapid increase in the number of identified genetic variants and the promise of identifying novel gene systems that we are not currently investigating, opening further doors in the study of gene functionality

Cognitive-electrophysiological indices of attentional and inhibitory processing in adults with ADHD: familial effects

Background Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. In a comparison of adults with ADHD and a matched control sample, we previously showed that abnormal inhibitory processing is typically preceded or accompanied by other processing deficits in adult ADHD. We now compare these data further to additional data from first-degree relatives (fathers) of children with ADHD to identify whether this pattern of abnormal processing shares familial influences with ADHD in adults. Methods Using a family design, we compared 20 fathers of children with the combined subtype of ADHD with 21 adults with ADHD combined subtype and 20 controls in event-related potential indices of preparatory states and subsequent response inhibition processing as elicited by a cued continuous performance task. Results Fathers of children with ADHD exhibited significantly weaker orienting attention to cues and inhibitory processing than the controls but not the ADHD sample. Conclusions These findings provide evidence for the familial association of attentional orienting and response inhibition processes with ADHD in adults and indicate a familial and neurobiological link between ADHD in children and adults

Altered EEG spectral power during rest and cognitive performance: a comparison of preterm-born adolescents to adolescents with ADHD

Preterm birth has been associated with an increased risk for ADHD-like behavioural symptoms and cognitive impairments. However, direct comparisons across ADHD and preterm-born samples on neurophysiological measures are limited. The aim of this analysis was to test whether quantitative EEG (QEEG) measures identify differences or similarities in preterm-born adolescents, compared to term-born adolescents with and without ADHD, during resting-state and cognitive task conditions. We directly compared QEEG activity between 186 preterm-born adolescents, 69 term-born adolescents with ADHD and 135 term-born control adolescents during an eyes-open resting-state condition (EO), which previously discriminated between the adolescents with ADHD and controls, and during a cued continuous performance task (CPT-OX). Absolute delta power was the only frequency range to demonstrate a significant group-by-condition interaction. The preterm group, like the ADHD group, displayed significantly higher delta power during EO, compared to the control group. In line with these findings, parent-rated ADHD symptoms in the preterm group were significantly correlated with delta power during rest. While the preterm and control groups did not differ with regard to absolute delta power during CPT-OX, the ADHD group showed significantly higher absolute delta power compared to both groups. Our results provide evidence for overlapping excess in the absolute delta range in preterm-born adolescents and term-born adolescents with ADHD during rest. During CPT-OX, preterm-born adolescents resembled controls. Increased delta power during rest may be a potential general marker of brain trauma, pathology or neurotransmitter disturbances

The Etiological and Predictive Association Between ADHD and Cognitive Performance From Childhood to Young Adulthood

Objective: Evidence about the etiology of the predictive associations between a diagnosis of ADHD and cognitive performance over time is scarce. Here, we examine these predictive and etiological patterns using a cross-lagged model design in a sample of 404 participants (74% males) from ADHD and control sibling pairs aged 6 to 17 years at baseline and 12 to 24 years at follow-up. Methods: Data included IQ, short-term and working memory measures, and response speed and variability from a four-choice reaction-time task. Results: ADHD and IQ predicted each other over time. ADHD at baseline predicted lower working memory performance at follow-up. Stable etiological influences emerged in the association between ADHD and cognitive variables across time. Conclusion: Whether early interventions can reduce negative interference with learning at school requires further study

Electrophysiological correlates of spontaneous mind wandering in attention-deficit/hyperactivity disorder

We recently hypothesised that increased spontaneous mind wandering (MW-S) reflects a core process underlying attention-deficit/hyperactivity disorder (ADHD). Previous studies show that individuals with ADHD and neurotypical individuals with increased MW-S display similar cognitive-performance and electrophysiological (EEG) impairments in attentional processes. However, the cognitive-EEG markers associated with increased MW-S in ADHD remain poorly understood. We therefore investigated such markers in a sample of 69 sex- and age-matched adults with ADHD and 29 controls during the Sustained Attention to Response Task. We compared task performance and EEG measures (P3, time-frequency brain-oscillations) of attentional processes between groups, and examined their association with a validated self-report questionnaire of MW-S. Finally, we tested the hypothesis that MW-S and ADHD diagnosis relate to the same cognitive-EEG impairments using a hierarchical regression model. Compared to controls, adults with ADHD showed attenuations in P3, event-related alpha and beta suppression during response inhibition (No-Go trials), and theta power activations during response execution (Go trials), as well as increased reaction time variability and more commission/omission errors. MW-S was also continuously associated with most cognitive-EEG measures related to ADHD. The hierarchical regressions on measures associated with both ADHD diagnosis and MW-S showed that MW-S did not explain additional variance in the cognitive-EEG markers (except for beta suppression) beyond ADHD diagnosis, and vice versa. These findings are consistent with our hypothesis that ADHD diagnosis and MW-S share common neural deficits, and that MW-S may reflect a core symptom of the disorder

ADHD Remission is linked to better neurophysiological error detection and attention-vigilance processes

Background: The processes underlying persistence and remission of attention-deficit/hyperactivity disorder (ADHD) are poorly understood. We aimed to examine whether cognitive and neurophysiological impairments on a performance monitoring task distinguish between ADHD persisters and remitters. Methods: On average six years after initial assessment, 110 adolescents and young adults with childhood ADHD (87 persisters, 23 remitters) and 169 age-matched controls were compared on cognitive-performance measures and event-related potentials (ERPs) of conflict monitoring (N2) and error processing (ERN, Pe) from an arrow flanker task with low- and high-conflict conditions. ADHD outcome was examined with parent-reported symptoms and functional impairment measures using a categorical (DSM-IV) and a dimensional approach. Results: ADHD persisters were impaired compared to controls on all cognitive-performance and ERP measures (all p<0.05). ADHD remitters differed from persisters, and were indistinguishable from controls, on the number of congruent (low-conflict) errors, reaction time variability (RTV), ERN and Pe (all p≤0.05). Remitters did not differ significantly from the other groups on incongruent (high-conflict) errors, mean reaction time and N2. In dimensional analyses on all participants with childhood ADHD, ADHD symptoms and functional impairment at follow up were significantly correlated with congruent errors, RTV and Pe (r=0.19-0.23, p≤0.05). Conclusions: Cognitive and neurophysiological measures of attention-vigilance and error detection distinguished ADHD remitters from persisters. These results extend our previous findings with other tasks (Cheung et al. 2015), and indicate that such measures are markers of remission and candidates for the development of non-pharmacological interventions

Barriers to and Facilitators of Using Remote Measurement Technology in the Long-Term Monitoring of Individuals With ADHD: Interview Study

BACKGROUND: Remote measurement technology (RMT) has the potential to address current research and clinical challenges of attention-deficit/hyperactivity disorder (ADHD) symptoms and its co-occurring mental health problems. Despite research using RMT already being successfully applied to other populations, adherence and attrition are potential obstacles when applying RMT to a disorder such as ADHD. Hypothetical views and attitudes toward using RMT in a population with ADHD have previously been explored; however, to our knowledge, there is no previous research that has used qualitative methods to understand the barriers to and facilitators of using RMT in individuals with ADHD following participation in a remote monitoring period. OBJECTIVE: We aimed to evaluate the barriers to and facilitators of using RMT in individuals with ADHD compared with a group of people who did not have a diagnosis of ADHD. We also aimed to explore participants' views on using RMT for 1 or 2 years in future studies. METHODS: In total, 20 individuals with ADHD and 20 individuals without ADHD were followed up for 10 weeks using RMT that involved active (questionnaires and cognitive tasks) and passive (smartphone sensors and wearable devices) monitoring; 10 adolescents and adults with ADHD and 12 individuals in a comparison group completed semistructured qualitative interviews at the end of the study period. The interviews focused on potential barriers to and facilitators of using RMT in adults with ADHD. A framework methodology was used to explore the data qualitatively. RESULTS: Barriers to and facilitators of using RMT were categorized as health-related, user-related, and technology-related factors across both participant groups. When comparing themes that emerged across the participant groups, both individuals with and without ADHD experienced similar barriers and facilitators in using RMT. The participants agreed that RMT can provide useful objective data. However, slight differences between the participant groups were identified as barriers to RMT across all major themes. Individuals with ADHD described the impact that their ADHD symptoms had on participating (health-related theme), commented on the perceived cost of completing the cognitive tasks (user-related theme), and described more technical challenges (technology-related theme) than individuals without ADHD. Hypothetical views on future studies using RMT in individuals with ADHD for 1 or 2 years were positive. CONCLUSIONS: Individuals with ADHD agreed that RMT, which uses repeated measurements with ongoing active and passive monitoring, can provide useful objective data. Although themes overlapped with previous research on barriers to and facilitators of engagement with RMT (eg, depression and epilepsy) and with a comparison group, there are unique considerations for people with ADHD, for example, understanding the impact that ADHD symptoms may have on engaging with RMT. Researchers need to continue working with people with ADHD to develop future RMT studies for longer periods

Commonalities in EEG Spectral Power Abnormalities Between Women With ADHD and Women With Bipolar Disorder During Rest and Cognitive Performance

While attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BD) denote distinct psy- chiatric conditions, diagnostic delineation is impeded by considerable symptomatic overlap. Direct comparisons across ADHD and BD on neurophysiological measures are limited. They could inform us on impairments that are specific to or shared between the disorders and, therefore, potential biomarkers that may aid in the identification of the diagnostic boundaries. Our aim was to test whether quantitative EEG (QEEG) identifies differences or imilarities between women with ADHD and women with BD during resting-state and task conditions. QEEG activity was directly compared between 20 ADHD, 20 BD and 20 control women during an eyes-open resting-state condition (EO) and a cued continuous performance task (CPT-OX). Both ADHD (t38 = 2.50, p = 0.017) and BD (t38 = 2.54, p = 0.018) participants showed higher absolute theta power during EO than controls. No significant differences emerged between the two clinical groups. While control participants showed a task-related increase in absolute theta power from EO to CPT-OX (t19 = -3.77, p = 0.001), no such change in absolute theta power was observed in the ADHD (t19 = -0.605, p = 0.553) or BD (t19 = 1.82, p = 0.084) groups. Our results provide evi- dence for commonalities in brain dysfunction between ADHD and BD. Absolute theta power may play a role as a marker of neurobiological processes in both disorders