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PubMed2026

Shared genetic architecture between ADHD and intelligence varies across ADHD subtypes.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous neurodevelopmental condition frequently accompanied by cognitive difficulties. Although previous genetic studies have demonstrated substantial overlap between ADHD and intelligence, most have treated ADHD as a single phenotype. However, whether this shared genetic architecture differs across ADHD subtypes remains unclear. METHODS: We conducted a genome-wide cross-trait analysis integrating large-scale genome-wide association study (GWAS) datasets of overall ADHD, its subtypes-childhood ADHD, persistent ADHD, and late-diagnosed ADHD-and intelligence (total N > 300,000). Genome-wide genetic correlations, polygenic overlap, local genetic correlations, and variant-level associations between ADHD phenotypes and intelligence were evaluated to characterize their shared genetic architecture. Shared variants were identified through cross-trait enrichment analyses and subsequently mapped to genes for functional annotation and gene-set enrichment. Bidirectional associations were evaluated using two-sample Mendelian randomization with sensitivity analyses. Additional GWAS datasets were used to validate the robustness of shared loci by assessing the consistency of effect directions. RESULTS: All ADHD phenotypes showed significant negative genetic correlations with intelligence (rg ranging from -0.3442 to -0.4205). Despite these modest genome-wide correlations, cross-trait analyses revealed substantial genetic overlap, including polygenic overlap, local genetic correlations, and variant-level associations. We identified 184 loci jointly associated with ADHD traits and intelligence, including 64 novel loci, whereas no shared loci were detected for persistent ADHD under the current analysis. Functional annotation revealed biologically distinct enrichment patterns across subtypes: childhood ADHD loci were linked to early neurodevelopmental processes, while late-diagnosed ADHD loci were enriched in synapse-related and neuronal signaling pathways. Mendelian randomization analyses suggested bidirectional associations, with stronger evidence supporting a directional association from intelligence to ADHD risk. Furthermore, these shared loci showed largely consistent effect directions across additional GWAS datasets, providing support for the robustness of the findings. CONCLUSIONS: The shared genetic architecture between ADHD and intelligence varies across ADHD subtypes, highlighting distinct biological pathways underlying cognitive heterogeneity in ADHD. These findings suggest that the relationship between ADHD liability and general cognitive ability is not uniform across ADHD subtypes and may inform future research on risk stratification and early identification in child and adolescent psychiatry.

Humans↗

PubMed2026

Antecedents and outcomes of a later attention-deficit hyperactivity disorder (ADHD) diagnosis in females.

BACKGROUND: Females are less likely than males to be diagnosed with attention-deficit hyperactivity disorder (ADHD). When diagnosed, females are older than males. AIMS: In this study, we examined the childhood antecedents of later ADHD diagnosis and its impact on adolescent/emerging adult outcomes, with a focus on females. METHOD: In this cohort study, we used data from a Welsh nation-wide electronic cohort of 13 593 individuals (n = 2680 (19.7%) females) diagnosed with ADHD and 578 793 individuals (n = 286 734 (49.5%) females) without ADHD. We compared females with later diagnoses (ages 12-25) to those with earlier, timely diagnoses (ages 5-11) and no diagnosis, in terms of childhood (ages 5-11) antecedents and adolescent/adult (ages 12-25) outcomes. We also tested for sex differences. RESULTS: Although females with earlier ADHD diagnosis showed more health and educational difficulties in childhood than those with later diagnosed ADHD (odds ratios ranged from 0.18 to 0.92), there was clear evidence of these difficulties in females with later diagnosed ADHD, compared with females without ADHD (odds ratios: 1.07-9.02). In adolescence/early adulthood, females with later diagnosed ADHD used more healthcare services and had worse mental health, educational and socioeconomic outcomes than females diagnosed earlier (odds ratios: 1.39-4.96) and those without ADHD (odds ratios: 1.54-23.98). Many of these outcomes were exacerbated in females compared with males. CONCLUSIONS: The results demonstrate that later ADHD diagnosis is associated with significant negative outcomes by adolescence and disproportionately disadvantages females. Despite later diagnosis, there was clear evidence of childhood mental health and educational difficulties when compared with females without ADHD. Therefore, timely childhood ADHD diagnosis may help to mitigate later risks, especially for females.

Attention–deficit hyperactivity disorder↗

PubMed2025

ADHD in Youth With Major Depressive Disorder in the Texas Youth Depression and Suicide Research Network (TX-YDSRN): Clinical Correlates and Moderators.

OBJECTIVE: Depression is a major public health concern with a 19% lifetime prevalence in youth, often precipitating other concerns, including suicidal behavior, poor school performance, and worsened peer relationships. ADHD is also common among youth and frequently presents alongside major depressive disorder (MDD), with this comorbidity associated with increased impairment. More research is needed to elucidate the clinical characteristics of this comorbidity (MDD + ADHD), especially as it relates to youth with MDD and no ADHD (MDD - ADHD). The present study examined the clinical correlates of MDD + ADHD in youth and the presence of an ADHD diagnosis as a moderator of the relationship between depressive symptoms and suicidality, peer relationships, and school functioning, respectively. METHODS: Our sample included 797 youth with MDD ages 8 to 20 years (Mage = 15.5 years) with and without ADHD. RESULTS: Youth with MDD + ADHD experienced more severe depressive symptoms, higher levels of suicidality, impulsivity, and irritability, and worse academic performance compared to those with MDD - ADHD. ADHD diagnosis did not moderate the relationships between depression severity and suicidality, peer relationships, or school functioning, respectively, suggesting that having an ADHD diagnosis may not affect these outcomes in depressed youth in this way. CONCLUSION: Findings shed light on the impact of ADHD in depressed youth, which may allow for earlier and more tailored intervention efforts aimed at identifying and targeting depression, suicidality, peer relationships, and school functioning.

Humans↗

PubMed1992

Follow-ups of children with attention deficit hyperactivity disorder (ADHD). Review of literature.

The purpose of this review has been to examine the hypothesis that the Attention Deficit Hyperactivity Disorder (ADHD), formerly also referred to as the Hyperactive Syndrome or Minimal Brain Dysfunction (MBD), is a precursor of criminality and abuse of alcohol and illicit drugs. This has been done by reviewing findings from follow-ups. Most reviewed projects suffer from methodological weakness. In most materials, few if any of the cases had ADHD according to present criteria. Some had ADHD and conduct problems. Many probably had exclusively conduct problems, but were too young to fulfill the criteria of Conduct Disorder (CD). Methodological limitations of the examined projects have been pointed out. It has been discussed how weaknesses regarding research design might have influenced the results. As a consequence of methodological shortcomings of most projects, the reviewed studies do not give definite answers. However, they show some rather convincing trends. By early adulthood, ADHD appears to remain present in at least one third of the subjects. Subjects with prior ADHD did not have more mental problems than controls in adolescence and early adulthood, provided they had normal intelligence, and no additional disabilities or mental disorders. Those with mental retardation, cerebral dysfunction or psychosis in addition to ADHD have a poor prognosis. A high percent become psychotic, and some end up in institutions. Although there seems to be an increased rate of delinquency and lawbreaking in prior hyperactives compared to controls, these differences disappear when the results are analyzed. The initially impressive differences between cases and controls are probably consequences of bias. Cases with a childhood history of conduct and educational problems have been compared to controls without a history of such problems. Thus, the reported differences are not related to ADHD. Hyperactives without conduct problems do not have an increased frequency of delinquency. Problems of conduct, CD and Antisocial Personality Disorder, but not psychosis characterize cases with a childhood history of conduct problems (with or without ADHD). In subjects with ADHD as well as conduct problems in childhood, conduct problems and not ADHD predict the prognosis, which is worse than for those with CD without ADHD. ADHD combined with delinquency indicates a high rate of subsequent lawbreaking. Usually, cases have more problems than controls with alcohol and illicit drugs, but this might be the consequence of selection of cases (subjects with school and conduct problems) and controls (subjects without such problems).(ABSTRACT TRUNCATED AT 400 WORDS)

Attention Deficit Disorder with Hyperactivity↗

PubMed1992

A developmental index using the Wechsler Intelligence Scale for Children: implications for the diagnosis and nature of ADHD.

The possible utility of Wechsler's Deterioration Index (WDI) in analyzing children's Wechsler Intelligence Scale for Children-Revised (WISC-R) results was explored in this study. Clinical records of children with learning disabilities (LD) and children with attention deficit-hyperactivity disorder (ADHD) were reviewed to determine if the WDI predicted the presence or severity of the disorders. The ages of the children ranged from 6 to 14. In two independent samples of children with LD (n = 35 and n = 26), the WDI did not predict LD status or severity. The LD samples were mostly male--85% and 57%, respectively. However, the WDI scores did significantly distinguish children with ADHD (n = 10) from nondisabled children (n = 10). The results were cross-validated on an independent sample of children with ADHD (n = 17) when compared to non-ADHD children (n = 22) who experienced significant behavioral difficulties. The ADHD samples were also mostly male--90% and 89%, respectively. The WDI classified only 59% of the children with ADHD and 86% of the non-ADHD children correctly. It is recommended that the WDI be considered a developmental index rather than a deterioration index in children. It is also recommended that significant WDI elevation (greater than .20) be considered to raise the question of ADHD, rather than simply yielding a diagnosis of ADHD.

Achievement↗

PubMed2026

Symptoms of Anxiety in Adults with ADHD: A Systematic Review and Meta-Analysis of Case-Control Studies.

OBJECTIVE: Research suggests there is a higher prevalence of anxiety in individuals with ADHD compared to those without ADHD. However, estimated prevalence rates vary greatly due to differences in methodologies used across studies. This study is the first meta-analysis investigating differences in anxiety measure scores between adults with and without ADHD, and possible moderators of this effect. METHOD: Our analysis included 58 studies that compared anxiety scores in adults with/without ADHD (N = 18,821; k = 112). RESULTS: The average effect size (Hedges's g) of anxiety scores in those with ADHD relative to controls was 0.77 (SE = 0.066); a medium effect. The only significant moderator was the type of comparison group used, with comparisons to non-clinical control groups (g = 0.954, SE = 0.08) yielding significantly larger effects than comparisons to clinical control groups (g = 0.437, SE = 0.09). None of the other moderator variables examined (Method of characterising ADHD, Anxiety Measure Type, Anxiety Measure Focus, Age or Gender) moderated the effect. There was some evidence of publication bias, therefore results should be interpreted with this in mind. CONCLUSION: Overall, this study indicates that ADHD is associated with higher levels of anxiety symptomology. This has important implications in the diagnosis and treatment of individuals presenting with ADHD or anxiety, including the consideration and screening of each of these conditions as potentially co-occurring with the other. Adaptions made to clinical practice in line with this would better support this population, improve symptom management and overall quality of life. Suggestions for future research are discussed.

Humans↗

PubMed1992

Attention, play, and social behavior in ADHD preschoolers.

We investigated attention, play and nonplay behavior in preschool children with attention deficit hyperactivity disorder (ADHD) and a matched control group of non-ADHD children. Forty 4- to 5-year-old children (20 ADHD and 20 matched control) participated. Across a 6-week-period, children's social and play interactions as well as nonplay behaviors were videotaped in the classroom. Videotape recordings were analyzed for the level of attention, cognitive play, and social participation. In addition, children's level of attention and cooperative behavior were observed during two group activities. Findings indicated that ADHD, relative to non-ADHD, children engaged in less overall play and greater functional or sensorimotor play. ADHD children also engaged in more transitional behavior, were less competent with peers, and were less attentive and cooperative during group activities.

Attention↗

PubMed2026

Psychiatric and neurological predictors of early ADHD medication discontinuation across the lifespan: a multinational study.

BACKGROUND: Early discontinuation of attention-deficit/hyperactivity disorder (ADHD) medication is common and linked to worse outcomes. Identifying clinical predictors could aid personalised treatment yet evidence is inconsistent across ages and countries/regions. OBJECTIVE: Investigate psychiatric and neurological comorbidity as predictors of early ADHD medication discontinuation in new ADHD medication users across age groups, sex and countries/regions. METHODS: Using health records from eight countries/regions, we identified 1 000 411 (44% female) new ADHD medication users (2011-2020). Discontinuation was defined as a ≥180 day gap between dispensations. We examined 23 indicators of psychiatric or neurological comorbidity, severity and psychotropic medication use. Associations were estimated using Cox regression, pooled with random-effects meta-analyses and stratified by age-at-initiation and sex. FINDINGS: Discontinuation rates varied widely (children 19%-61%, adolescents 37%-68%, young adults 52-67%, adults 38%-68%). In pooled analyses, earlier discontinuation in children was predicted by intellectual disability, autism and use of psychotropic medications (HR range 1.32-1.51), while conduct/oppositional defiant disorder (CD/ODD) was protective (HR 0.83, 95% CI 0.73 to 0.94). In adolescents, no indicators remained statistically significant after multiple-testing control. In young adults, CD/ODD (HR 1.42, 95% CI 1.30 to 1.55), and in adults, schizophrenia (HR 1.25, 95% CI 1.09 to 1.44) and tic disorders (HR 1.27, 95% CI 1.11 to 1.46) predicted earlier discontinuation. Statistical heterogeneity was substantial, largely driven by US estimates. In meta-analyses excluding the USA, additional associations emerged. For example, in children, OCD and anxiety disorders predicted earlier discontinuation, while eating disorders and antidepressants/anxiolytics were protective in adults. Associations with schizophrenia, tic disorders and CD/ODD were no longer significant. Country-specific analyses showed similar association patterns, except in the USA, Hong Kong and the UK. Sex differences were limited. CONCLUSIONS: Children with neuropsychiatric comorbidity and related comedication are more likely to discontinue ADHD medication early, whereas few consistent predictors were seen from adolescence onwards. Marked cross-country variation, particularly in the USA, points to system-level influences on treatment patterns. CLINICAL IMPLICATIONS: Improving ADHD medication persistence will require consideration of healthcare context and age-specific strategies, including close monitoring for children with complex neuropsychiatric profiles, and consideration of broader factors in adolescents and adults, where clinical predictors were limited.

Humans↗

PubMed1992

Use of a verbal fluency measure in understanding and evaluating ADHD as an executive function disorder.

A primary characteristic of Attention Deficit Hyperactivity Disorder (ADHD) is an inability to establish and maintain sustained attention, which is speculated to reflect frontal lobe involvement. The Knight Verbal Fluency measure was administered to 19 ADHD inpatient boys and to a cohort group of 7 children who were matched for mean age, psychiatric diagnosis (depression), treatment facility, and examiner but were without the diagnosis of ADHD. Analysis indicated that ADHD children performed significantly lower than expected and lower than the similar non-ADHD children. These findings lend support to the hypothesis that frontal lobe dysfunction is involved in attentional process disorders and suggests the potential clinical usefulness in the diagnostic screening of ADHD children of a simply administered measure amenable to interpretation of frontal lobe function.

Adolescent↗

PubMed2026

The effect of tDCS on emotion-related risk-taking behavior and delay discounting in adults with ADHD.

INTRODUCTION: Adults with Attention Deficit Hyperactivity Disorder (ADHD) often engage in risky behaviors due to impaired decision-making processes. This study aims to investigate the effects of transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC) on emotion-related risk-taking behavior and delay discounting in adults with ADHD. METHODS: Thirty adults with ADHD underwent three tDCS conditions, administered in a randomized order with at least one week between sessions: (1) left dlPFC anode/right vmPFC cathode, (2) left dlPFC cathode/right vmPFC anode, and (3) sham stimulation. In each session, participants completed the Delay Discounting Task (DDT) and the Modified Balloon Analogue Risk Task (mBART) under three emotional conditions (neutral, positive, and negative) which were induced using emotionally congruent photographs and sounds. Galvanic skin responses (GSR) were also recorded. In the DDT, both area under the curve (AUC) values and log-transformed discounting rates (log k) were calculated for small, medium, and large reward magnitudes (RM). Exploratory electric field modeling was also performed to characterize current distribution. RESULTS: The findings demonstrated task-specific effects of tDCS on decision-making. Although no overall tDCS effect was observed on DDT performance, significant tDCS × RM interactions emerged, particularly for smaller rewards. In contrast, exploratory analyses suggested that tDCS affected all mBART scores. Emotional condition did not influence consistently behavioral performance in either task, whereas both emotional stimulation and tDCS significantly affected GSR responses. However, exploratory electric field modeling indicated a broad prefrontal current distribution extending beyond the intended cortical targets. CONCLUSIONS: These findings suggest preliminary evidence that prefrontal tDCS can influence risk-related decision-making and autonomic responses in adults with ADHD. However, its effects on delay discounting appear to be context-dependent and limited to specific RMs. Future studies combining neuroimaging with individualized electric field modeling are needed to clarify the neural mechanisms underlying the observed effects of tDCS and to optimize stimulation protocols in adults with ADHD.

Humans↗

PubMed1992

Methylphenidate response in aggressive and nonaggressive ADHD children: distinctions on laboratory measures of symptoms.

Response to a single, 5-mg dose of methylphenidate was compared in aggressive and nonaggressive attention-deficit hyperactivity disorder (ADHD) children using objective measures of inattention, impulsivity, and activity level. After medication, both ADHD groups had a significant decrease in inattention, whereas impulsivity remained unchanged. Activity level decreased only in the nonaggressive ADHD group. Unmedicated normal controls showed no change on any measure. These results support the hypothesis that aggressive and nonaggressive ADHD children have somewhat different underlying determinants for some of their symptoms. In addition, they suggest that inattention, impulsivity, and overactivity may be mediated by partially distinct neural mechanisms.

Aggression↗

PubMed2005

No evidence for the association of DRD4 with ADHD in a Taiwanese population within-family study.

BACKGROUND: Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent and highly heritable childhood disorder. The dopamine D4 receptor (DRD4) gene has shown a genetic association with ADHD in Caucasian populations with meta-analysis indicating a small but significant effect across datasets. It remains uncertain whether this association can be generalised to non-Caucasian ethnic groups. Here we investigate two markers within the DRD4 gene in a Taiwanese population, the exon 3 variable number tandem repeat (VNTR) and a 5' 120 base-pair duplication. METHODS: Within-family transmission disequilibrium tests of association of the 5' 120 base-pair duplication, and exon 3 VNTR in a Taiwanese population. RESULTS: No evidence of association of ADHD with either polymorphism in this population was observed. CONCLUSION: The DRD4 gene markers investigated were not found to be associated with ADHD in this Taiwanese sample. Further work in Taiwanese and other Asian populations will therefore be required to establish whether the reports of association of DRD4 genetic variants in Caucasian samples can be generalised to Asian populations.

Adolescent↗

PubMed2025

Improving Community-Based Care for Adolescents with ADHD: a Randomized Controlled Trial of Artificial Intelligence-Assisted Fidelity Supports.

Cognitive-behavioral treatments (CBTs) for adolescents with ADHD demonstrate promise of long-term effects on outcome. However, their implementation in routine care community clinics faces barriers that impact quantity, efficiency, and quality of delivery, as well as client outcomes. This study is a randomized controlled trial designed to evaluate the impact of an AI-assisted service delivery model on therapist implementation of Supporting Teens' Autonomy Daily (STAND), a CBT blended with Motivational Interviewing (MI) for adolescents with ADHD. Adolescents with ADHD (N = 51), who were clients at three community mental health agencies, received treatment from 23 therapists. There was randomization of adolescents and therapists to AI-assisted or standard implementation supports. In addition to standard supports (i.e., training, standard facilitation resources, technical assistance, case supervision), AI-assisted support package included digitized facilitation resources housed in a clinical dashboard (Care4), feedback on content fidelity, and AI-generated feedback on MI implementation quality. The AI-assisted group was associated with more efficient treatment delivery and lower number of appointments attended by the adolescent. There was also a significant decrement in MI quality over time in the AI-assisted group compared to the standard support group. Feedback in focus groups indicated that therapists perceived a task-oriented mindset to be associated with receipt of the AI-assisted support package, leading therapists to prioritize efficiency over relational aspects of therapy. Following the results of this trial, a future, larger RCT should examine the impact of the AI-assisted implementation model on mental health outcomes and cost savings to organizations, third party payers, and clients. Trial registration number: NCT05135065; https://www.clinicaltrials.gov ; Registered September 2021.

Humans↗

PubMed2026

Exploring Immersive Virtual Reality as an Approach to Improve School Participation-Related Constructs in Children With ADHD.

BACKGROUND: School participation is frequency and involvement from person-environment transactions, not diagnosis, per the International Classification of Functioning, Disability and Health (ICF) and the family of participation-related constructs (fPRC). In this framework, the environmental and child determinants of school participation (e.g., school routines and peer/teacher context; self-regulation, activity competence and preferences) interact bidirectionally to shape everyday participation. However, many interventions still target isolated impairments, overlooking coordinated changes in capacities and context. Grounded in this contemporary view, this study aimed to investigate the impact of an immersive virtual reality (IVR) intervention on school participation-related constructs in children with ADHD. METHODS: The study included 92 children aged between 7 and 12 years diagnosed with ADHD. Participants were randomly assigned into intervention (n = 46) and control (n = 46) groups. Both groups completed the School Participation Questionnaire (SPQ) and Bruininks-Oseretsky Test of Motor Proficiency Test 2 Brief Form (BOT2-BF) assessment prior to the intervention. The intervention group received an IVR intervention program twice a week for 8 weeks. During this period, the control group did not receive additional therapy. At the end of the 8 weeks, the SPQ was readministered to both groups. RESULTS: Baseline characteristics showed no significant differences in SPQ and BOT2-BF results between groups, confirming homogeneity prior to intervention. Following the intervention, the study group demonstrated significant improvements across all domains of the SPQ (doing, being, symptoms and environment), with large effect sizes for SPQ total score (d = 0.978) and subdomains (d = 0.452-0.910). In contrast, the control group showed no improvements and even declines in subdomains. Post-intervention, between-group comparisons revealed significant differences favouring the study group across all domains (p < 0.001), with large effect sizes (d = 0.878-1.165). CONCLUSIONS: Findings suggest that the IVR program was associated with improvements in teacher-rated environmental and child determinants of school participation (SPQ domains) in children with ADHD.

Humans↗

PubMed2026

A Systematic Review of Lived Experiences of Receiving a Diagnosis of ADHD in Adulthood.

OBJECTIVE: With rising numbers of adults seeking and receiving ADHD diagnoses, understanding their first-hand experiences of the diagnostic process is key for sensitive support and service design. This systematic review collates, evaluates and synthesises the existing evidence-base on lived experiences of adult ADHD diagnosis. METHOD: Keyword searches of six databases generated 10,357 citations, which were subjected to a systematic screening process that identified 21 relevant studies. Findings were analysed using thematic synthesis. RESULTS: Analysis generated three overarching themes, elaborating how diagnostic experiences are shaped by adults' Relationship with Self, Relationship with Others, and Relationship with Systems. Personally, diagnosis was widely experienced as a pivotal identity event, triggering biographical reflection that could foster greater self-compassion, but also grief, anger and identity confusion. Socially, diagnosis facilitated interpersonal understanding and communication, but also exposed adults to stigma and introduced dilemmas about diagnostic disclosure. Systemically, adults experienced the diagnostic process as beset by barriers and delays, and reported highly variable access to post-diagnosis supports or treatment. CONCLUSION: Results suggest receiving an ADHD diagnosis in adulthood is a complex relational process that can be both validating and destabilising, with variation in experiences resulting from individual biographies, interpersonal resources, stigma climates, and service structures.

Humans↗

PubMed1992

Learning styles of LD and NLD ADHD children.

Attention Deficit Hyperactive Disorder (ADHD) children (N = 26) with a learning disability (LD) and without (NLD) were compared on measures of information processing using the Learning Efficiency Test (LET). Method of presentation (visual vs. auditory), order of recall (ordered vs. non-ordered), and memory processes (immediate, short-term, and long-term) were assessed. While both groups showed more difficulty with short-term and long-term memory processes than with immediate memory processes, the ADHD-LD subjects demonstrated more difficulty processing information effectively. Ordered recall was significantly more difficult for both short-term and long-term memory processes than was unordered recall. While both groups demonstrated difficulty with auditory ordered recall under short-term and long-term conditions, the ADHD-LD subjects lost the most information under auditory conditions.

Adolescent↗

PubMed1992

The spontaneously hypertensive rat (SHR) as an animal model of childhood hyperactivity (ADHD): changed reactivity to reinforcers and to psychomotor stimulants.

Childhood hyperactivity (attention-deficit hyperactivity disorder, ADHD) is a behavior disorder affecting 2-6% of grade-school children. The main symptoms are attention problems and hyperkinesis. The disorder is commonly treated with psychomotor stimulants, usually methylphenidate hydrochloride (ritalin) or d-amphetamine. Neither the cause of the disorder nor the basis of the effectiveness of the drug treatment is well understood. Differences in reinforcement processes have been implicated as part of the underlying problem. The main purpose of the present research was to investigate reinforcement processes and motor characteristics with and without stimulant medication in SHR, as an animal model of ADHD, and WKY controls, its normoactive progenitor strain. SHR behavior turned out to be more sensitive to immediate reinforcement and proportionately less sensitive to delayed reinforcement when compared to the behavior of WKY, as demonstrated by systematic changes in rates of responding throughout fixed-interval schedules of reinforcement of bar-presses by water. The psychomotor stimulants weakened the control by immediate reinforcers and strengthened the control by delayed reinforcers, with the effect of the drugs being more pronounced in WKY than in SHR. The results are consistent with clinical observations that ADHD children are less willing than others to accept "delayed gratification" and that methylphenidate increases the control of delayed reward over their behavior.

Analysis of Variance↗

PubMed1992

Contextual factors in vigilance testing of children with ADHD.

The effect of contextual factors on continuous performance testing was examined by administering a vigilance task to 51 children with ADHD under conditions of examiner presence and absence at different times (i.e., beginning and middle) of an assessment battery. The results showed that the ability to differentiate target stimuli from distractors (d-prime) was related to examiner presence vs. absence, and that response bias (beta), a measure of the subject's carefulness in responding to stimuli, was associated with the time of task administration. The decline in d-prime under conditions of examiner absence was shown to be related more to level of aggression as opposed to level of inattention. Children with ADHD having relatively high levels of aggression demonstrated a significant decline in d-prime scores under conditions of examiner absence, but those with relatively low levels of aggression did not. The results demonstrated the importance of contextual factors on vigilance task performance and suggested a differential impact of contextual variables on children who are inattentive vs. aggressive.

Aggression↗