ADHD and Behavioral Inhibition: A Re-examination of the Stop-signal Task

The current study investigates two recently identified threats to the construct validity of behavioral inhibition as a core deficit of attention-deficit/hyperactivity disorder (ADHD) based on the stop-signal task: calculation of mean reaction time from go-trials presented adjacent to intermittent stop-trials, and non-reporting of the stop-signal delay metric. Children with ADHD (n = 12) and typically developing (TD) children (n = 11) were administered the standard stop-signal task and three variant stop-signal conditions. These included a no-tone condition administered without the presentation of an auditory tone; an ignore-tone condition that presented a neutral (i.e., not associated with stopping) auditory tone; and a second ignore-tone condition that presented a neutral auditory tone after the tone had been previously paired with stopping. Children with ADHD exhibited significantly slower and more variable reaction times to go-stimuli, and slower stop-signal reaction times relative to TD controls. Stop-signal delay was not significantly different between groups, and both groups’ go-trial reaction times slowed following meaningful tones. Collectively, these findings corroborate recent meta-analyses and indicate that previous findings of stop-signal performance deficits in ADHD reflect slower and more variable responding to visually presented stimuli and concurrent processing of a second stimulus, rather than deficits of motor behavioral inhibition.     

Working Memory Deficits in Boys with Attention-deficit/Hyperactivity Disorder (ADHD): The Contribution of Central Executive and Subsystem Processes

The current study investigated contradictory findings from recent experimental and meta-analytic studies concerning working memory deficits in ADHD. Working memory refers to the cognitive ability to temporarily store and mentally manipulate limited amounts of information for use in guiding behavior. Phonological (verbal) and visuospatial (nonverbal) working memory were assessed across four memory load conditions in 23 boys (12 ADHD, 11 typically developing) using tasks based on Baddeley's (Working memory, thought, and action, Oxford University Press, New York, 2007) working memory model. The model posits separate phonological and visuospatial storage and rehearsal components that are controlled by a single attentional controller (CE: central executive). A latent variable approach was used to partial task performance related to three variables of interest: phonological buffer/rehearsal loop, visuospatial buffer/rehearsal loop, and the CE attentional controller. ADHD-related working memory deficits were apparent across all three cognitive systems--with the largest magnitude of deficits apparent in the CE--even after controlling for reading speed, nonverbal visual encoding, age, IQ, and SES.     

Written expression in boys with ADHD: The mediating roles of working memory and oral expression

The written expression difficulties experienced by children with ADHD are widely recognized; however, scant empirical evidence exists concerning the cognitive mechanisms and processes underlying these deficiencies. The current study investigated the independent and potentially interactive contributions of two developmentally antecedent cognitive processes – viz., working memory (WM) and oral expression – hypothesized to influence written expression ability in boys. Thirty-three boys with ADHD-Combined Presentation and 27 neurotypical (NT) boys 8–12 years of age were administered standardized measures of oral and written expression, and multiple counterbalanced tasks to assess WM central executive (CE) processes, WM phonological short-term memory (PH STM), and WM visuospatial short-term memory (VS STM). Bias-corrected bootstrapped mediation analyses revealed a significant mediation effect, wherein the independent and interactive effects of PH STM and oral expression collectively explained 76% of the diagnostic status to written expression relation. The implications of the obtained results for clinical practice suggest that children with ADHD may benefit by incorporating a blended approach that simultaneously strengthens PH STM capacity and oral expression abilities as antecedents to engaging in writing-related activities.     

Classroom observations of students with and without ADHD: Differences across types of engagement

The current study examined the behaviors related to academic engagement exhibited by students with ADHD during instruction in math and reading. A total of 155 students (92 ADHD, 63 recruited controls) in grades 1 through 4 participated in the study. Results revealed that students with ADHD exhibited statistically significant lower rates of academic engagement and higher rates of off-task behaviors than recruited controls and randomly selected peer comparisons. Specifically, students with ADHD exhibited statistically significant lower rates of passive academic engagement (PET) than recruited controls and peer comparisons; however no group differences were found with regard to active engaged time (AET). In addition, students with ADHD exhibited lower rates of AET than PET, a finding observed among both recruited controls and randomly selected peer comparisons. Implications for research and practice are discussed.     

Response Style Differences in the Inattentive and Combined Subtypes of Attention-Deficit/Hyperactivity Disorder

This study examined potential differences between the inattentive and combined ADHD subtypes using laboratory tasks assessing behavioral inhibitory processes. Seventy-five children completed two tasks of behavioral inhibition believed to isolate different processes: the cued reaction time task (CRT), a basic inhibition task, and the go/no-go task (GNG), a complex inhibition task that incorporates motivational contingencies. Three groups of participants were identified, including ADHD/Inattentive (n = 17), ADHD/Combined (n = 37), and comparison (n = 21). Results indicated that rather than showing behavioral inhibition deficits, the ADHD/I children appeared overly inhibited, as evidenced by slower reaction times across the two tasks and significantly higher errors of omission in the GNG task. Additionally, the ADHD/I children did not demonstrate cue dependency effects on the CRT task, suggesting that they were failing to incorporate relevant information before making a response. The sluggish and inhibited performance of the ADHD/I group challenges the idea that it is a subtype of ADHD.     

The Predictive Validity of Parent and Teacher Reports of ADHD Symptoms

The objectives were to evaluate the ability of the Inattention and Hyperactivity–Impulsivity factors of the ADHD Rating Scale-IV to differentiate children with ADHD from a control group and to discriminate children with different subtypes of ADHD. Also, we sought to determine optimal cutoff scores on the teacher and parent versions of this scale for making diagnostic decisions about ADHD. In a sample of 92 boys and girls 6 to 14 years of age referred to a regional ADHD program, we assessed ADHD diagnostic status using categorical and dimensional approaches as well as parent- and teacher-report measures. Logistic regression analyses showed that the Inattention and Hyperactivity–Impulsivity factors of the ADHD Rating Scale-IV were effective in discriminating children with ADHD from a control group and differentiating children with ADHD, Combined Type from ADHD, Inattentive Type. Although both teacher and parent ratings were significantly predictive of diagnostic status, teacher ratings made a stronger contribution to the prediction of subtype membership. Using symptom utility estimates, optimal cutoff scores on the Inattention and Hyperactivity–Impulsivity scales for predicting subtypes of ADHD were determined.     

The clinical utility of behavior rating scales: Comments on the diagnostic assessment of ADHD

Responding to Reid and Maag's critique of behavior rating scales in assessing ADHD, published in a previous issue of the Journal of School Psychology, we provided specific recommendations for improving the accuracy of diagnostic decisions using rating scales and affirmed the importance of these procedures in the assessment of ADHD. Strategies for managing the error intrinsic to the use of diagnostic measures, specifically behavior rating scales, were outlined. A multiple stage procedure, involving one or more levels of screening prior to conducting a diagnostic assessment, was recommended as a strategy to increase diagnostic accuracy in a time- and cost-efficient manner.     

Internal Validity of the Disruptive Behavior Disorder Symptoms: Implications from Parent Ratings for a Dimensional Approach to Symptom Validity

A dimensional approach was used to evaluate the internal validity of the DSM-III-R ADHD-inattention, ADHD-hyperactivity/impulsivity, oppositional defiant disorder (ODD), and conduct disorder (CD) symptoms (i.e., whether a symptom has a stronger correlation with its own dimension than the other three). Parents rated 4,019 children between the ages of 2 and 19 on these symptoms. The results showed that 5 of the 6 inattention symptoms, 3 of the 4 hyperactivity symptoms, 1 of the 4 impulsivity symptoms, 6 of the 9 oppositional defiant disorder symptoms, and 8 of the 11 CD symptoms had significant internal validity. Confirmatory factor analysis (CFA) found support for inattention, hyperactivity/impulsivity, oppositional defiant, and conduct disorder dimensions. Multiple-group CFA also found support for factor pattern and loading invariance across gender. The implications of these results as well as the merits of the dimensional approach to symptom validity are discussed in the context of the DSM-IV changes in ADHD, ODD, and CD.     

Effects of White Noise on Off-Task Behavior and Sleep for Elementary-Age Students with ADHD

Abstract

Children with ADHD were administered 75?dB of continuous white noise during independent seat work in the classroom and during bedtime in their homes. Compared to baseline all three students exhibited decreases in off-task behavior. Off-task behavior returned to original baseline levels when white noise was removed and decreased again when reintroduced in classrooms. White noise also decreased bedtime sleep latency and spontaneous night wakings at home. Both sleep latencies and night wakings increased during return-to-baseline conditions. Surprisingly, when white noise was reintroduced only in the classrooms sleep improved a second time. White noise in classrooms with or without simultaneous treatment during sleep at night resulted in lower levels of off-task classroom behavior as well as less disruptive sleep. Results were independent of whether children were on ADHD medication. Children, teachers, and parents all rated white noise favorably.     

Multimodal Treatments for Childhood Attention-deficit/Hyperactivity Disorder: Interpreting Outcomes in the Context of Study Designs

The goal of this article was to outline issues critical to evaluating the literature on incremental benefit of multiple effective treatments used together, vs. a single effective treatment, for childhood ADHD. These issues include: (1) sequencing and dosage of treatments being combined and compared; (2) difficulty drawing valid conclusions about individual components of treatment when treatment packages are employed; (3) differing results emerging from measurement tools that purportedly measure the same domain; and (4) the resultant difficulty in reaching a summary conclusion when multiple outcome measures yielding conflicting results are used. The implications of these issues for the design and conduct of future studies are discussed, and recommendations are made for future research.     

Age of Onset of ADHD in a Sample of Elementary School Students

Examined the age of onset of ADHD symptoms and subtypes using parent ratings of a large sample of elementary school students. Results showed: (1) in children with ADHD-combined type, hyperactive-impulsive symptoms emerged at younger ages than inattention symptoms; (2) about one-fifth of children who met symptom count and impairment criteria for ADHD did not meet the age of onset criterion; (3) Children who did not meet the age of onset criterion consisted primarily of children with inattention problems; and (4) children who did not meet the age of onset criterion had more impaired parent-child relationships, self-esteem, family functioning, and higher overall impairment ratings than children who did meet the criterion. These results raise questions about the validity of the age of onset criterion for ADHD as formulated in DSM-IV.     

Teachers' and education students' perceptions of and reactions to children with and without the diagnostic label "ADHD"

Thirty-four elementary school teachers and 32 education students from Canada rated their reactions towards vignettes describing children who met attention-deficit/hyperactivity disorder (ADHD) symptom criteria that included or did not include the label “ADHD.” “ADHD”-labeled vignettes elicited greater perceptions of the child's impairment as well as more negative emotions and less confidence in the participants, although it also increased participants' willingness to implement treatment interventions. Ratings were similar to vignettes of boys versus girls; however, important differences in ratings between teachers and education students emerged and are discussed. Finally, we investigated the degree to which teachers' professional backgrounds influenced bias based on the label “ADHD.” Training specific to ADHD consistently predicted label bias, whereas teachers' experience working with children with ADHD did not.     

A Comparison of the Neuropsychological Profiles of the DSM-IV Subtypes of ADHD

Recent research on the DSM-IV subtypes of attention-deficit/hyperactivity disorder (ADHD) has demonstrated that the subtypes differ in demographic characteristics, types of functional impairment, and profiles of comorbidity with other childhood disorders. However, little research has tested whether the subtypes differ in underlying neuropsychological deficits. This study compared the neuropsychological profiles of children without ADHD (n = 82) and children who met symptom criteria for DSM-IV Predominantly Inattentive subtype (ADHD-IA; n = 67), Predominantly Hyperactive Impulsive subtype (ADHD-HI; n = 14), and Combined subtype (ADHD-C; n = 33) in the areas of processing speed, vigilance, and inhibition. We hypothesized that children with elevations of inattention symptoms (ADHD-IA and ADHD-C) would be impaired on measures of vigilance and processing speed, whereas children with significant hyperactivity/impulsivity (ADHD-HI and ADHD-C) would be impaired on measures of inhibition. Contrary to prediction, symptoms of inattention best predicted performance on all dependent measures, and ADHD-IA and ADHD-C children had similar profiles of impairment. In contrast, children with ADHD-HI were not significantly impaired on any dependent measures once subclinical symptoms of inattention were controlled. Our results do not support distinct neuropsychological deficits in ADHD-IA and ADHD-C children, and suggest that symptoms of inattention, rather than symptoms of hyperactivity/impulsivity, are associated with neuropsychological impairment.     

Relating lab to life: Decrements in attention over time predict math productivity among children with ADHD

A child’s ability to sustain attention over time (AOT) is critical in attention-deficit/hyperactivity disorder (ADHD), yet no prior work has examined the extent to which a child’s decrement in AOT on laboratory tasks relates to clinically-relevant behavior. The goal of this study is to provide initial evidence for the criterion validity of laboratory assessments of AOT. A total of 20 children with ADHD (7–12 years of age) who were enrolled in a summer treatment program completed two lab attention tasks (a continuous performance task and a self-paced choice discrimination task) and math seatwork. Analyses focused on relations between attention task parameters and math productivity. Individual differences in overall attention (OA) measures (averaged across time) accounted for 23% of the variance in math productivity, supporting the criterion validity of lab measures of attention. The criterion validity was enhanced by consideration of changes in AOT. Performance on all laboratory attention measures deteriorated as time-on-task increased, and individual differences in the decrement in AOT accounted for 40% of the variance in math productivity. The only variable to uniquely predict math productivity was from the self-paced choice discrimination task. This study suggests that attention tasks in the lab do predict a clinically-relevant target behavior in children with ADHD, supporting their use as a means to study attention processes in a controlled environment. Furthermore, this prediction is improved when attention is examined as a function of time-on-task and when the attentional demands are consistent between lab and life contexts.     

Differences Between ADHD Inattentive and Combined Types on the CPT

Two samples of school-age boys with attention-deficit/hyperactivity disorder (ADHD-Combined and ADHD-Inattentive Types) and a non-ADHD control group were administered an AX version of the continuous performance task (CPT) to examine specific sustained attention deficits. Three levels of time-on-task were included to study performance declines, and 3 interstimulus intervals were included to examine vigilance deficits. As predicted by R. A. Barkley's and H. C. Quay's behavior inhibition deficit models (R. A. Barkley, 1997; H. C. Quay, 1997), the performance of the ADHD-Combined Type (ADHD-C) participants deteriorated more quickly than the other samples. No significant evidence of vigilance deficits among the inattentive (ADHD-IA) sample was found. These findings suggest that distinct criteria for the two ADHD subtypes may be warranted when the CPT is used for diagnostic assessment, and sustained attention-related declines in performance may be typical of the ADHD-C Type only.     

Associations of Lifetime Depression with Trauma Exposure,Other Environmental Adversities,and Impairment in Adolescents with ADHD

Depression is a common, potentially devastating comorbidity in youth with attention-deficit/hyperactivity disorders (ADHD). Various environmental adversities are well-described as correlates of depression in general pediatric populations, but not in youth with ADHD. In 104 adolescents with ADHD, we examined potential environmental correlates of lifetime depression, including trauma exposure, recent negative life events and current parent-child conflict, along with current and past ADHD severity and current impairment. Controlling for demographic variables, comorbid disorders, and ADHD severity, we noted significant associations between lifetime depression and environmental adversities, including victimization trauma, parent-child conflict, and behaviorally-independent negative life events. Current impairment but not ADHD severity was also highly associated with lifetime depression, controlling for the same covariates. Findings from this preliminary, cross-sectional study suggest that environmental adversities and impairment in youth with ADHD should also be targeted along with the ADHD when contemplating strategies to treat or prevent comorbid depression.     

Executive Functioning, Temporal Discounting, and Sense of Time in Adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and Oppositional Defiant Disorder (ODD)

Clinic-referred teens (ages 12–19) with ADHD and ODD (N = 101) were compared to community control (CC) teens, equated for age and sex, (N = 39) on a variety of psychological tasks assessing executive functioning (EF), temporal reward discounting, and time estimation and reproduction. A factor analysis reduced the EF measures to three dimensions, representing CPT Inattention, Working Memory, and CPT Inhibition. Results indicated that the ADHD group had significantly more CPT Inattention than the CC group. No differences were found for Working Memory or CPT Inhibition. The ADHD group displayed significantly greater temporal discounting of delayed hypothetical monetary rewards relative to immediate ones and manifested more impaired time reproduction, but not time estimation, than did the CC group. Main effects for level of IQ were found only on the Working Memory factor and largely did not interact with the group factor otherwise. The group differences in CPT Inattention, temporal discounting, and time reproduction were not a function of level of comorbid oppositional defiant disorder, delinquency, or anxiety–depression. Results are reasonably consistent with past research on EF and sense of time in children with ADHD and extend these findings to the adolescent age group. Problems with working memory and CPT inhibition found in prior studies of children with ADHD, however, were not evident here, perhaps owing to age-related improvements or insufficient task difficulty.     

Working memory and behavioral inhibition in children with attention-deficit/hyperactivity disorder (ADHD): an examination of varied central executive demands,construct overlap,and task impurity

The stop-signal paradigm is the premier metric of behavioral inhibition in contemporary attention-deficit/hyperactivity disorder (ADHD) research. The stop-signal paradigm’s choice-reaction time component, however, arguably places greater demands on working memory processes (e.g., controlled-focused attention) relative to alternative inhibition metrics (i.e., go/no-go (GNG) tasks), and consequently obscures conclusions about inhibition and working memory deficits in affected children. The current study, therefore, aimed to determine whether shared variance between stop-signal behavioral inhibition and working memory performance in children with ADHD reflects overlap between the working memory and inhibition constructs or insufficient specificity of the stop-signal paradigm. Fifty-five children (8–12 years) with and without ADHD were administered established phonological (PH) and visuospatial (VS) working memory measures, as well as stop-signal and GNG tasks that vary with respect to demands on controlled-focused attention. Although working memory and GNG performance each uniquely predicted children’s inattention, stop-signal task performance was not a significant predictor of unique variance in inattention, above and beyond variance associated with working memory. Collectively, these findings suggest that performance on the stop-signal task, compared to the GNG task, is confounded by greater demands associated with working memory and consequently reflects an impure estimate of the inhibition construct.     

Innovations in Assessing ADHD: Development, Psychometric Properties, and Factor Structure of the ADHD Symptoms Rating Scale (ADHD-SRS)

This research involved the development of a behavior rating scale designed to measure ADHD and the investigation of the scale's psychometric properties and factor structure. This scale, the ADHD Symptoms Rating Scale (ADHD-SRS), was developed for the assessment of ADHD in the school-age (K–12) population. Participants were 1006 children and adolescents (in grades K–12) who were rated by their parents and/or teachers. The results indicate that the ADHD-SRS possesses strong internal consistency reliability and test–retest reliability and moderate cross-informant reliability. The data also suggest that the ADHD-SRS has strong content validity. Convergent validity of this instrument was also high, as demonstrated by correlations with three previously validated behavior rating scales. Significant age and gender differences in ADHD symptoms were found with both the parent and teacher respondent populations. Finally, the factor analysis of the ADHD-SRS suggested a two factor oblique rotation as the best fit for both the parent and the teacher data. After a visual inspection of the items which loaded on each factor, Factor 1 was named Hyperactive-Impulsive and Factor 2 was named Inattention. These two factors, along with the items which loaded on each factor, appear to be remarkably similar to the two categories listed in the DSM-IV for ADHD. Directions for future research, as well as clinical implications and limitations of the research are discussed.