Genetic overlap between ADHD symptoms and EEG theta power

Biological markers that are grounded in neuroscience may facilitate understanding of the pathophysiology of complex psychiatric disorders. One of the most consistent and robust neural abnormalities in attention deficit hyperactivity disorder (ADHD) is increased EEG power in the theta band at rest (4–8 Hz). The present study used a twin design to estimate the extent of genetic overlap between increased theta power and risk for ADHD in order to validate theta power as a marker of genetic risk for ADHD. At rest, EEG was measured in 30 monozygotic and dizygotic adolescent twin pairs concordant or discordant for high ADHD symptom scores and 37 monozygotic and dizygotic control twin pairs with low ADHD symptom scores. Structural equation modelling was used to estimate the heritability of theta power and partition the genetic and environmental contributions to the overlap between ADHD and theta power. A significant phenotypic correlation between ADHD symptoms and elevated theta power was found. Theta power demonstrated moderate to high heritability estimates (0.77) and moderate genetic correlations with ADHD (0.35) suggesting shared genetic influences. Increased theta power is a candidate biological marker of genetic risk for ADHD, which warrants further investigation of the neurobiological mechanisms that underlie the genetic relationship.     

Visual attention control differences in 12-month-old preterm infants

There have been few previous attempts to assess the development of early markers of executive function in infants born preterm despite well-established deficits reported for older preterm children that have been closely linked to poorer academic functioning. The present study investigates early attention control development in healthy 12-month-old age-corrected pre-term infants who were born less than 30 weeks and compares their performance to full-term infants. Eye-tracking methodology was used to measure attention control. Preterm Infants spent less time focused on the target and were slower to fixate attention, with lower gestational age associated with poorer target fixation and slower processing speed. There were no significant group differences observed for inhibition of return or interference control. These findings suggest that specific emerging deficits in attention control may be observed using eye tracking methodology in very preterm infants at this early stage of development, despite scores within the average range on the Bayley Scales of Infant Development.     

Gray’s revised Reinforcement Sensitivity Theory in relation to Attention-Deficit/Hyperactivity and Tourette-like behaviors in the general population

Attention-Deficit/Hyperactivity Disorder (ADHD) and Tourette syndrome (TS) present as distinct conditions clinically; however, they show comorbidity and inhibitory control deficits have been proposed to underlie both. The role of reinforcement sensitivity in ADHD has been studied previously, but no study has addressed this in relation to TS-like behaviors in the general population. The present study examined these associations within the remit of the revised Reinforcement Sensitivity Theory (rRST). One hundred and thirty-eight participants completed psychometric measures of the rRST, and self-report checklists for ADHD- and TS-like behaviors. The results show that whilst ADHD-inattention was only linked to increased anxiety (BIS), ADHD-hyperactivity/impulsivity was linked to increased impulsivity (BAS-fun seeking), anxiety (BIS) and punishment sensitivity (FFFS), and to reduced reward sensitivity (BAS-reward responsiveness), independently of ‘comorbid’ TS-like behaviors. TS-related phonic tics were associated with increased BIS and FFFS, and TS-related obsessive–compulsive behaviors (OCBs) with increased goal-orientation (BAS-drive) and reduced impulsivity (BAS-fun seeking). However, these associations were driven by ADHD-like behaviors or OCB co-occurrence, respectively, suggesting little role of the rRST in pure TS-like behaviors. The results are discussed in light of mixed findings in the literature and the importance of distinguishing between multiple processing models of the rRST in distinct disorder phenotypes.     

Processing Speed Deficits in Attention Deficit/Hyperactivity Disorder and Reading Disability

The goal of the current study was to test whether deficits in processing speed (PS) may be a shared cognitive risk factor in reading disability (RD) and Attention Deficit/Hyperactivity Disorder (ADHD), which are known to be comorbid. Literature on ADHD and RD suggests that deficits on tasks with a speeded component are seen in both of these disorders individually. The current study examined a wide range of speeded tasks in RD, ADHD, comorbid RD+ADHD, and a control group to test whether RD and ADHD have similar profiles of PS deficits, and whether these deficits are shared by the two disorders. The results suggest that a general PS deficit exists in both clinical groups compared to controls, although children with RD demonstrate greater PS deficits than children with ADHD. Two tests (underadditivity and partial correlations) were conducted to test whether these PS deficits are shared. Since we found that PS deficits were underadditive in the comorbid group and that partialling PS reduced the correlation between RD and ADHD, it appears that PS is a shared cognitive risk factor that may help explain the comorbidity of these two disorders.     

Online Story Comprehension among Children with ADHD: Which Core Deficits are Involved?

Children with ADHD have difficulty understanding causal connections and goal plans within stories. This study examined mediators of group differences in story narrations between children ages 7-9 with and without ADHD, including as potential mediators both the core deficits of ADHD (i.e., inattention, disinhibition, planning/working memory) as well measures of phonological processing and verbal skills. Forty-nine children with ADHD and 67 non-referred children narrated a wordless book and completed tasks assessing the core deficits of ADHD, phonological processing, and verbal skills. Results revealed that, although no shorter than those of non-referred children, the narratives of children with ADHD contained fewer elements relating to the story's causal structure and goal plan. Deficits in sustained attention accounted for the most variance in these differences. Results have implications for understanding and ameliorating the academic problems experienced by children with ADHD.     

Resilient Adolescent Adjustment Among Girls: Buffers of Childhood Peer Rejection and Attention-Deficit/Hyperactivity Disorder

Examined a risk-resilience model of peer rejection and attention-deficit/hyperactivity disorder (ADHD) in a 5-year longitudinal study of 209 ethnically and socioeconomically diverse girls aged 6-13 at baseline and 11-18 at follow-up. Risk factors were childhood ADHD diagnosis and peer rejection; hypothesized protective factors were childhood measures of self-perceived scholastic competence, engagement in goal-directed play when alone, and popularity with adults. Adolescent criterion measures were multi-informant composites of externalizing and internalizing behavior plus indicators of academic achievement, eating pathology, and substance use. ADHD and peer rejection predicted risk for all criterion measures except for substance use, which was predicted by ADHD only. ADHD and peer rejection predicted lower adolescent academic achievement controlling for childhood achievement, but they did not predict adolescent externalizing and internalizing behavior after controlling for baseline levels of these constructs. Regarding buffers, self-perceived scholastic competence in childhood (with control of academic achievement) predicted resilient adolescent functioning. Contrary to hypothesis, goal-directed play in childhood was associated with poor adolescent outcomes. Buffers were not found to have differential effectiveness among girls with ADHD relative to comparison girls.     

Recognition memory and awareness: A high-frequency advantage in the accuracy of knowing

The well-established advantage of low-frequency words over high-frequency words in recognition memory has been found to occur in remembering and not knowing. Two experiments employed remember and know judgements, and divided attention to investigate the possibility of an effect of word frequency on know responses given appropriate study conditions. With undivided attention at study, the usual low-frequency advantage in the accuracy of remember responses, but no effect on know responses, was obtained. Under a demanding divided attention task at encoding, a high-frequency advantage in the accuracy of know responses was obtained. The results are discussed in relation to theories of knowing, particularly those incorporating perceptual and conceptual fluency.     

Sport-Based Group Therapy Program for Boys with ADHD or with Other Behavioral Disorders

A group of children with Attention Deficit Hyperactivity Disorder (ADHD) was compared to children with other behavior and emotional problems. All the participants participated together in 20 weekly sessions for 1 academic year. The participants were assessed with three questionnaires on three different occasions: before the beginning of the group, at the completion of the group, and 1 year after the completion of the group. The results showed that the children indicated improvement in two behavior domains while their parents indicated improvement in the children's behavior in five domains. The most striking improvement was reduction of anxiety.     

Setting Generalization during Self-Reinforcement with Educationally Handicapped Children

Eight educationally handicapped boys ranging in age form 10 to 11 years old and described as the worst behavior problems in their class participated in a series of single-subject studies carried out in their self-contained classrooms. Three served as target subjects, using self-reinforcement procedures to increase their sustained on-task behavior in a treatment setting; five served as generalization subjects. Data were collected in three settings within the self-contained classroom; an early morning treatment setting, a late morning generalization setting, and an afternoon generalization setting. The three target subjects averaged a 51% increase over their baseline median levels of sustained on-task behavior in the treatment setting. They averaged 84% and 96% generalization to the late morning and afternoon generalization settings, respectively. These results demonstrate that self-reinforcement can produce setting generalization of treatment effects in the absence of prior externally determined reinforcement. Evidence for subject and subject-setting generalization was also obtained.     

Interference Effects in a Numerical Stroop Paradigm in 9- to 12-year-old Children with ADHD-C

Attention deficit hyperactivity disorder (ADHD) is characterized by deficient self-regulation, poor attentional control, and poor response inhibition. To date, however, the extent to which these deficits affect basic interference control remains a matter of controversy. Secondly, ADHD has been reported to be associated with arithmetic deficits. It remains unclear whether such deficits are a secondary consequence of the above-mentioned characteristics of ADHD or whether basic numerical magnitude representations are also affected. In the present study we attempted to investigate these issues using a basic numerical interference paradigm.

Nine- to twelve-year-old children with ADHD-C (attention-deficit hyperactivity-disorder combined type) and control children without ADHD (each n = 16) were presented with two digits of possibly different physical sizes (e.g., 3 7). This numerical Stroop task requires subjects to make a magnitude classification concerning either the physical or the numerical stimulus dimension. The irrelevant dimension can be congruent (same response), incongruent (different response), or neutral (no response association).

Children with ADHD-C performed worse than control children in most analyses. The most important finding was a significant interaction of congruity effects with group in the numerical comparison task. Children with ADHD-C tended to show larger congruity and interference effects than controls, and these were not attributable to a speed-accuracy trade-off.

The results might reflect differential processing speeds, or a different degree of automatic activation of physical and numerical magnitudes in children with and without ADHD-C. Alternative explanations, such as insufficient inhibition of selective (domain-specific) attention are also discussed.