John O. Simon

Evidence for Higher Reaction Time Variability for Children With ADHD on a Range of Cognitive Tasks Including Reward and Event Rate Manipulations

OBJECTIVE The purpose of the research study was to examine the manifestation of variability in reaction times (RT) in children with attention deficit hyperactivity disorder (ADHD) and to examine whether RT variability presented differently across a variety of neuropsychological tasks, was present across the two most common ADHD subtypes, and whether it was affected by reward and event rate (ER) manipulations. METHOD Children with ADHD-combined type (n = 51), ADHD-predominantly inattentive type (n = 53), and 47 controls completed five neuropsychological tasks (Choice Discrimination Task, Child Attentional Network Task, Go/No-Go task, Stop Signal Task, and N-back task), each allowing trial-by-trial assessment of RTs. Multiple indicators of RT variability including RT standard deviation, coefficient of variation and ex-Gaussian tau were used. RESULTS Children with ADHD demonstrated greater RT variability than controls across all five tasks as measured by the ex-Gaussian indicator tau. There were minimal differences in RT variability across the ADHD subtypes. Children with ADHD also had poorer task accuracy than controls across all tasks except the Choice Discrimination task. Although ER and reward manipulations did affect childrens RT variability and task accuracy, these manipulations largely did not differentially affect children with ADHD compared to controls. RT variability and task accuracy were highly correlated across tasks. Removing variance attributable to RT variability from task accuracy did not appreciably affect between-groups differences in task accuracy. CONCLUSIONS High RT variability is a ubiquitous and robust phenomenon in children with ADHD.

Parent Agreement on Ratings of Children's Attention Deficit/Hyperactivity Disorder and Broadband Externalizing Behaviors.

Mothers and fathers often disagree in their ratings of child behavior, as evidenced clinically and as supported by a substantial literature examining parental agreement on broadband rating scales. The present study examined mother—father agreement on Diagnostic and Statistical Manual—based symptom-specific ratings of Attention-Deficit/Hyperactivity Disorder (ADHD), as compared to agreement on broadband ratings of externalizing behavior. Based on mother and father ratings of 324 children who participated in the Multimodal Treatment Study of Children with ADHD (MTA), parental agreement was computed and patterns of disagreement examined. Mother—father ratings were significantly correlated; however, a clear pattern of higher ratings by mothers was present. Agreement on attention-deficit/hyperactivity disorder symptom-specific ratings was significantly lower than that for broadband externalizing behaviors and oppositional defiant disorder symptoms. Of several moderator variables tested, parental stress was the only one that predicted the discrepancy in ratings. Disagreement between parents is clinically significant and may pose complications to the diagnostic process.Mothers and fathers often disagree in their ratings of child behavior as evidenced clinically and supported by a substantial literature examining parental agreement on broadband rating scales. The present study examined mother-father agreement on DSM-based, ADHD symptom-specific ratings, as compared to agreement on broadband ratings of externalizing behavior. Using mother and father ratings from 324 children who participated in the Multimodal Treatment Study of Children with ADHD, parental agreement was computed and patterns of disagreement were examined. Mother-father ratings were significantly correlated. However, a clear pattern of higher ratings by mothers compared to fathers was present across ratings. Agreement on ADHD symptom-specific ratings was significantly lower than agreement for broadband externalizing behaviors or ODD symptoms. Of several moderator variables tested, parental stress was the only variable that predicted the discrepancy in ratings. Disagreement between parents is clinically significant and may pose complications to the diagnostic process.

Effects of Stimulant Medication, Incentives, and Event Rate on Reaction Time Variability in Children With ADHD

This study examined the effects of methylphenidate (MPH) on reaction time (RT) variability in children with attention deficit hyperactivity disorder (ADHD). Using a broad battery of computerized tasks, and both conventional and ex-Gaussian indicators of RT variability, in addition to within-task manipulations of incentive and event rate (ER), this study comprehensively examined the breadth, specificity, and possible moderators of effects of MPH on RT variability. A total of 93 children with ADHD completed a 4-week within-subject, randomized, double-blind, placebo-controlled crossover trial of MPH to identify an optimal dosage. Children were then randomly assigned to receive either their optimal MPH dose or placebo after which they completed five neuropsychological tasks, each allowing trial-by-trial assessment of RTs. Stimulant effects on RT variability were observed on both measures of the total RT distribution (ie, coefficient of variation) as well as on an ex-Gaussian measure examining the exponential portion of the RT distribution (ie, τ). There was minimal, if any, effect of MPH on performance accuracy or RT speed. Within-task incentive and ER manipulations did not appreciably affect stimulant effects across the tasks. The pattern of significant and pervasive effects of MPH on RT variability, and few effects of MPH on accuracy and RT speed suggest that MPH primarily affects RT variability. Given the magnitude and breadth of effects of MPH on RT variability as well as the apparent specificity of these effects of MPH on RT variability indicators, future research should focus on neurophysiological correlates of effects of MPH on RT variability in an effort to better define MPH pharmacodynamics.

Parent- Teacher Agreement on ADHD Symptoms Across Development

Parent-teacher agreement on attention-deficit/hyperactivity disorder (ADHD) symptom ratings ranges from low to moderate. Most studies evaluating parent-teacher agreement have not assessed measurement invariance across raters. Hence, it is unclear whether discordance across raters is due to differing ADHD constructs across raters or other factors (e.g., subjective differences across raters). Additionally, the effect of development on parent-teacher agreement is relatively unknown. To address these limitations, the present study used parent and teacher ADHD ratings from a large (N = 6,659) developmentally diverse (ages 4-17) sample. Using exploratory structural equation modeling on half the sample, and then confirmatory factor analysis (CFA) on the other half of the sample, confirmed a 2-factor structure with significant cross-loadings for the 18 ADHD symptoms. CFA invariance analyses demonstrated that the 2-factor symptom structure was similar across raters and age groups. After confirming measurement invariance, the correlation between latent factors within and across raters was examined for each age group as well as across age groups. Parents reported greater severity of ADHD symptoms than did teachers, and both parents and teachers reported higher levels of hyperactivity/impulsivity in younger children than in older children and consistent levels of inattention across development. Finally, correlations between parent-teacher ratings of like factors were weak for inattention and moderate-strong for hyperactivity/impulsivity, and the magnitude of parent-teacher agreement did not vary across development. In conclusion, while parent and teacher ratings of ADHD behaviors are only weakly to moderately correlated, each reporter provides unique and valid clinical information as it relates to ADHD symptom presentation.

The relationship between ADHD symptom dimensions, clinical correlates, and functional impairments.

Objective: To better understand how heterogeneity in attention-deficit hyperactivity disorder (ADHD) symptoms relates to heterogeneity in functional impairment domains in children with ADHD after accounting for demographic variables and comorbidities, in particular oppositionality and internalizing symptoms. Methods: Parents and teachers (n = 5663) rated child/adolescent impairments across impairment domains in the International Classification of Functioning, Disability and Health as well as symptoms of ADHD and comorbidities. Hierarchical regressions were conducted to assess the relationship between parent and teacher ratings of ADHD symptom domains and functional impairments after accounting for personal factors and comorbid disorders. Results: Symptoms of inattention were the strongest predictors of ratings of academic (math, writing, and so on) functioning, while hyperactivity/impulsivity symptoms were the strongest predictor of classroom disruption even after accounting for the presence of learning disorders and oppositional symptoms. Symptoms of ADHD accounted for minimal variance in interpersonal functioning or participation in organized activities after controlling oppositional symptoms. Conclusion: The ADHD symptom domains demonstrate domain-specific relations with various ADHD-related functional impairments. In addition, the results highlight the role of oppositionality in interpersonal relationship difficulties and participation in organized activities.

Does Sluggish Cognitive Tempo Fit Within a Bi-Factor Model of ADHD?

Objective: Studies demonstrate sluggish cognitive tempo (SCT) symptoms to be distinct from inattentive and hyperactive-impulsive dimensions of ADHD. No study has examined SCT within a bi-factor model of ADHD, whereby SCT may form a specific factor distinct from inattention and hyperactivity/impulsivity while still fitting within a general ADHD factor, which was the purpose of the current study. Method: A total of 168 children were recruited from an ADHD clinic. Most (92%) met diagnostic criteria for ADHD. Parents and teachers completed measures of ADHD and SCT. Results: Although SCT symptoms were strongly associated with inattention, they loaded onto a factor independent of ADHD g. Results were consistent across parent and teacher ratings. Conclusion: SCT is structurally distinct from inattention as well as from the general ADHD latent symptom structure. Findings support a growing body of research suggesting SCT to be distinct and separate from ADHD.

Improved but still impaired: symptom-impairment correspondence among youth with attention-deficit hyperactivity disorder receiving community-based care.

Objective: To explore correspondences between the trajectories of symptoms and impairments in youth with attention-deficit hyperactivity disorder (ADHD) being treated by in primary care settings. Methods: Parents of youth (n = 1976) rated their childs symptoms of inattention and hyperactivity/impulsivity, and impairment across a variety of domains. Multilevel models were estimated to characterize the trajectories of symptoms and impairment and to determine whether changes in symptom dimension trajectories corresponded to changes in impairment trajectories over time. Results: Results indicated that symptom dimensions initially improved, then leveled off, and then decreased minimally. However, impairment domains remained largely stable (i.e., neither improved nor worsened). Improvement in inattention symptoms were associated with improved ratings of writing impairment, and improved ratings of hyperactivity/impulsivity symptoms were associated with improved relationship with peers. Conclusions: Youths with ADHD who are treated by their community pediatrician tend to initially improve in their symptom presentation, although this symptom reduction plateaus and is not associated with corresponding improvements in most areas of impairment.

Mediators of methylphenidate effects on math performance in children with attention-deficit hyperactivity disorder.

Objective: Stimulant medications, such as methylphenidate (MPH), improve the academic performance of children with attention-deficit hyperactivity disorder (ADHD). However, the mechanism by which MPH exerts an effect on academic performance is unclear. We examined MPH effects on math performance and investigated possible mediation of MPH effects by changes in time on-task, inhibitory control, selective attention, and reaction time variability. Methods: Children with ADHD aged 7 to 11 years (N = 93) completed a timed math worksheet (with problems tailored to each individuals level of proficiency) and 2 neuropsychological tasks (Go/No-Go and Child Attention Network Test) at baseline, then participated in a 4-week, randomized, controlled, titration trial of MPH. Children were then randomly assigned to their optimal MPH dose or placebo for 1 week (administered double-blind) and repeated the math and neuropsychological tasks (posttest). Baseline and posttest videorecordings of children performing the math task were coded to assess time on-task. Results: Children taking MPH completed 23 more math problems at posttest compared to baseline, whereas the placebo group completed 24 fewer problems on posttest versus baseline, but the effects on math accuracy (percent correct) did not differ. Path analyses revealed that only change in time on-task was a significant mediator of MPHs improvements in math productivity. Conclusions: MPH-derived math productivity improvements may be explained in part by increased time spent on-task, rather than improvements in neurocognitive parameters, such as inhibitory control, selective attention, or reaction time variability.

Reasons Why Children and Adolescents With Attention-Deficit/Hyperactivity Disorder Stop and Restart Taking Medicine

Abstract To describe the prevalence of reasons why children and adolescents stop and restart attention-deficit/hyperactivity disorder (ADHD) medicine and whether functional impairment is present after stopping medicine. We used the prospective longitudinal cohort from the Multimodal Treatment of Study of Children with ADHD. At the 12 year follow-up when participants were a mean of 21.1 years old, 372 participants (76% male, 64% Caucasian) reported ever taking ADHD medicine. Participants reported the age when they last stopped and/or restarted ADHD medicine and also endorsed reasons for stopping and restarting. Seventy-seven percent (286/372) reported stopping medicine for a month or longer at some time during childhood or adolescence. Participants were a mean of 13.3 years old when they last stopped medicine. The most commonly endorsed reasons for stopping medication related to 1) medicine not needed/helping, 2) side effects, 3) logistical barriers of getting/taking medication, and 4) social concerns/stigma. Seventeen percent (64/372) reported restarting medicine after stopping for a month or longer. Commonly endorsed reasons for restarting related to 1) medicine needed/helped, 2) resolution of logistical barriers to getting/taking. For both stopping and restarting, the proportion endorsing some reasons differed by age range, with the overall pattern suggesting that parental involvement in decisions decreased with age. Nearly all participants had impairment at the assessment after stopping regardless of whether medication was resumed. Different reasons for stopping and/or restarting medicine are relevant at different times for different teens. Tailored strategies may help engage adolescents as full partners in their treatment plan.OBJECTIVE To describe the prevalence of reasons why children and adolescents stop and restart attention-deficit/hyperactivity disorder (ADHD) medicine and whether functional impairment is present after stopping medicine. METHODS We used the prospective longitudinal cohort from the Multimodal Treatment of Study of Children With ADHD. At the 12-year follow-up, when participants were a mean of 21.1 years old, 372 participants (76% male, 64% white) reported ever taking ADHD medicine. Participants reported the age when they last stopped and/or restarted ADHD medicine and also endorsed reasons for stopping and restarting. RESULTS Seventy-seven percent (286 of 372) reported stopping medicine for a month or longer at some time during childhood or adolescence. Participants were a mean of 13.3 years old when they last stopped medicine. The most commonly endorsed reasons for stopping medication related to 1) medicine not needed/helping, 2) adverse effects, 3) logistical barriers of getting or taking medication, and 4) social concerns or stigma. Seventeen percent (64 of 372) reported restarting medicine after stopping for a month or longer. Commonly endorsed reasons for restarting related to medicine being needed or medicine helping; and resolution of logistical barriers to getting or taking medicine. For both stopping and restarting, the proportion endorsing some reasons differed by age range, with the overall pattern suggesting that parental involvement in decisions decreased with age. Nearly all participants had impairment at the assessment after stopping, regardless of whether medication was resumed. CONCLUSIONS Different reasons for stopping and/or restarting medicine are relevant at different times for different teens. Tailored strategies may help engage adolescents as full partners in their treatment plan.