Attention-deficit/hyperactivity Disorder Symptom Domains Research Articles

Towards an Objective Measurement Tool for ADHD-like Traits in Family Dogs: A Comprehensive Test Battery.

Family dogs exhibit neuropsychological deficits similar to attention-deficit/hyperactivity disorder (ADHD) symptoms in humans. Questionnaire methods have mostly been used to assess ADHD-like behaviours in dogs. In addition to our validated questionnaire (Dog ADHD and Functionality Rating Scale-DAFRS; 2024), we developed a simple behavioural test battery covering the ADHD symptom domains (i.e., inattention, hyperactivity, and impulsivity) in dogs. Our main aim was (i) to provide a final external validation step to the DAFRS by examining its associations with the test variables (N = 59); and (ii) to compare owner- and trainer-rated factor scores' associations with the test variables (n = 38). We developed four tests covering the ADHD symptom domains: the attention test (inattention), the plush dog test (impulsivity), the leash test, and the sit test (hyperactivity). All four behavioural variables correlated with their respective questionnaire scores, i.e., the strongest for hyperactivity, and the least strong for inattention. Both owner- and trainer-rated scores (n = 38) correlated with the relevant test variables in an expected direction. Dogs' training status was linked only to the sit test results. Test-retest analyses (n = 34) indicated moderate-to-excellent agreement across all behavioural variables. Our findings support the validity of our novel human-analogue questionnaire for dogs as the behavioural tests strongly correlate with the relevant questionnaire scores, indicating that the two constructs together can effectively assess inattention, hyperactivity, and impulsivity in dogs.

Longitudinal network model of the co-development of temperament, executive functioning, and psychopathology symptoms in youth with and without ADHD.

Attention Deficit Hyperactivity Disorder (ADHD) is a common, chronic, and impairing disorder, yet presentations of ADHD and clinical course are highly heterogeneous. Despite substantial research efforts, both (a) the secondary co-occurrence of ADHD and complicating additional clinical problems and (b) the developmental pathways leading toward or away from recovery through adolescence remain poorly understood. Resolving these requires accounting for transactional influences of a large number of features across development. Here, we applied a longitudinal cross-lagged panel network model to a multimodal, multilevel dataset in a well-characterized sample of 488 children (nADHD=296) to test Research Domain Criteria initiative-inspired hypotheses about transdiagnostic risk. Network features included DSM symptoms, trait-based ratings of emotional functioning (temperament), and performance-based measures of cognition. Results confirmed that ADHD symptom domains, temperamental Irritability, and Working Memory are independent transdiagnostic risk factors for psychopathology based on their direct associations with other features across time. ADHD symptoms and working memory each had direct, independent associations with depression. Results also demonstrated tightly linked co-development of ADHD symptoms and temperamental Irritability, consistent with the possibility that this type of anger dysregulation is a core feature that is co-expressed as part of the ADHD phenotype for some children.

Neuropsychological deficits in relation to ADHD symptoms, quality of life, and daily life functioning in young adulthood

Attention-deficit/hyperactivity disorder (ADHD) is related to multiple neuropsychological deficits. However, most previous studies, especially studies of adult samples, have not taken the overlap between different neuropsychological deficits into account. In addition, the link between neuropsychological deficits and daily life functioning and quality of life needs to be further investigated. The aim was therefore to investigate the independent effects of executive deficits, delay-related behaviors and emotion dysregulation on ADHD symptom levels, daily life functioning, and quality of life in a non-clinical sample of younger adults. Results showed independent effects of all three neuropsychological deficits on the two ADHD symptom domains. With regard to daily life functioning and quality of life, bivariate relations were found to all three neuropsychological deficits. However, it was primarily the associations to executive deficits that remained significant when studying independent effects. Executive deficits were related to daily life functioning and quality of life also when controlling for ADHD symptom levels. Conclusively, this study shows that ADHD is related to multiple neuropsychological deficits, even in adulthood. Previous studies may have overestimated the importance of delay-related behaviors and emotion dysregulation for daily life functioning, as they have failed to control for the effects of executive deficits.

“Tomorrow is the busiest day of the week”: Executive functions mediate the relation between procrastination and attention problems

Objective We examined whether executive functions (EFs) mediate the relation between procrastination and attention-deficit/hyperactivity disorder (ADHD) symptoms in college students. Participants: One hundred fourteen undergraduates were recruited for study participation. Methods: Participants completed measures of academic performance, procrastination, ADHD symptoms, EFs (as measured by five EF facets: time management, organization/problem-solving, restraint, motivation, and emotion regulation), and common comorbid concerns for college students between May 2017 and May 2018. A mediational framework was utilized to examine the associations among procrastination, EFs, and four ADHD symptoms domains. Results: Results indicated that both procrastination and GPA correlated with EFs and three ADHD symptom domains. While EFs mediated the association between procrastination and ADHD symptoms, follow-up analyses suggested that self-management of time and organization/problem-solving are the specific pathways through which procrastination is indirectly associated with ADHD symptoms. Conclusions: Promising areas for future research and potential intervention targets are discussed.

The effects of childhood inattention and anxiety on executive functioning: inhibition, updating, and shifting.

Although anxiety and attention-deficit/hyperactivity disorder (ADHD) symptoms are highly comorbid, research has generally examined the executive functioning (EF) deficits associated with each of these symptoms independently. The purpose of this study was to examine the unique and interactive effects of anxiety and ADHD symptoms (first respectively, then collectively) on multiple dimensions of EF (i.e., inhibition, updating, and shifting, respectively). A sample of 142 youth from the community (age range 8-17years; Mage = 11.87 ± 2.94years) completed the Delis-Kaplan Executive Function System and dimensional measures of anxiety, inattention, and hyperactivity/impulsivity. It was hypothesized that anxiety would moderate the effect of ADHD symptomatology on EF. Multiple regression models examined anxiety and ADHD symptom domains as predictors of EF. When examining ADHD symptom domains separately, anxiety moderated the relationship between inattention and both updating and shifting; the association between hyperactivity/impulsivity and updating was also moderated by anxiety. Within the full model including both ADHD symptom domains, results indicated that anxiety moderated the relationship between inattention and shifting. Analyses of ADHD symptoms in separate and combined models demonstrated a similar pattern: Increased inattention was associated with worse EF and when anxiety was a significant moderator, and increased ADHD symptoms were associated with worse EF only for those with high levels of anxiety. These results highlight the utility of including anxiety in studies examining the relationship between ADHD and EF. EF is related to multiple aspects of daily functioning (e.g., academic achievement), and EF deficits are often targeted in interventions for ADHD.

Effect of zinc supplementation in zinc-deficient children with attention-deficit hyperactivity disorder

Background Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder increasing in prevalence. Although there is limited evidence to support treating ADHD with mineral supplements, research does exist showing that patients with ADHD may have reduced levels of zinc, ferritin, and magnesium. These nutrients have important roles in neurologic function, including involvement in neurotransmitter synthesis. In spite of the good response of many patients with ADHD to stimulant drugs, a substantial percent do not respond to or develop significant side effects from stimulants. For this reason, zinc treatment has been considered to show positive results on various symptoms in ADHD patients with zinc deficiency. Objectives The aim of this study is to elucidate the effect of zinc supplementation on ADHD symptoms in zinc-deficient ADHD children. Patients and methods Thirty zinc-deficient children diagnosed with ADHD and on a fixed dose of methylphenidate were enrolled in this study. They were assigned to zinc supplementation (30 mg/day) as gluconate in an open-label follow-up trial for 10 weeks. Results There was a statistically significant difference among zinc-deficient ADHD children before and after zinc supplementation on all working memory index subtest scores and all Conner’s subscale scores. This result points to the effect of zinc supplementation on ADHD symptom domains.

Prevalence and clinical correlates of insomnia in adults with attention-deficit hyperactivity disorder.

To investigate the prevalence of insomnia in adults with Attention-deficit hyperactivity disorder (ADHD) and its association with clinical subtypes, current ADHD symptoms, and stimulant treatment. We obtained diagnostic information, symptom rating scales and treatment history from clinically ascertained adult ADHD patients diagnosed according to DSM-IV criteria (n = 268, mean age 38.1 years) and randomly selected population controls (n = 202, mean age 36.5 years). The Bergen Insomnia Scale (BIS) was used to measure insomnia. ADHD symptom domains were self-rated using the Adult ADHD Self-Rating Scale. Insomnia was far more frequent among adults with ADHD (66.8%) than in the population controls (28.8%) (P < 0.001). Insomnia was more common in adults with the combined subtype than in those with the inattentive subtype (79.7% and 55.6%, respectively) (P = 0.003). For self-reported current ADHD symptoms, inattention was strongly correlated to insomnia. Patients currently using stimulant treatment for ADHD reported a lower total insomnia score compared to patients without medication (P < 0.05). Insomnia was highly prevalent among adults with ADHD. The lower insomnia score in patients on current stimulant treatment suggests that stimulant treatment is not associated with worsening of insomnia symptoms in adult ADHD patients.

Predicting ADHD Symptoms in Adolescence from Early Childhood Temperament Traits.

Extreme levels of certain temperament traits can be early markers of different developmental pathways of attention-deficit/hyperactivity disorder (ADHD). However, the long-term utility of using these traits as predictors of ADHD is not fully known. This study includes 64 male adolescents (M age=13.5), who have been followed since birth as part of a longitudinal study. The primary aim was to test effortful control (EC), activity level, and anger, measured in early childhood - both with mother's reports and laboratory assessments -as predictors of ADHD symptoms in adolescence. Further, we investigated the specificity of this prediction to the different ADHD symptom domains. The results demonstrated that early temperament dimensions of EC and activity level were predictive of ADHD symptoms about 10years later, when the participants reached adolescence. Moreover, activity level showed specificity only to hyperactivity-impulsivity symptoms whereas EC was a predictor of the two symptom domains. Anger had a predictive correlation with ADHD symptoms; however, it did not have a unique predictive contribution. These results emphasize the relevance of EC and activity level in the developmental course of ADHD. Identification of early risk factors can lead to more efficient design and implementation of intervention programs.

Secondhand Smoke Exposure and Low Blood Lead Levels in Association With Attention-Deficit Hyperactivity Disorder and Its Symptom Domain in Children: A Community-Based Case-Control Study.

Aim:Secondhand smoke (SHS) is a major indoor pollutant. We examined the possible association between exposure to both SHS and low levels of lead and attention-deficit–hyperactivity disorder (ADHD) and its symptom domain in children.Methods:This case–control study was based on the results of a community survey using the ADHD rating scale conducted in 49 elementary schools. Both cases and control subjects were confirmed by a child psychiatrist. Each case was matched with one control subject according to gender, school, and grade in school. Using a multivariate conditional logistic regression model, we analyzed 214 case–control pairs of children who ranged in age from 6 to 10 years. Urine and blood levels of cotinine and of lead were determined, and information pertaining to SHS exposure was obtained by means of a questionnaire.Results:Exposure to low levels of lead (geometric mean = 1.65 µg/dL) was related to ADHD, particularly inattention (odds ratio [OR] = 1.67, 95% confidence interval [CI] = 1.07–2.59), whereas SHS exposure was associated mainly with hyperactivity/impulsivity (OR = 3.85, 95% CI = 1.55–9.56). In the pathway from blood lead to hyperactivity/impulsivity, children’s SHS exposure mediated and indirectly accounted for about 73% of this relationship. The combined exposure to lead and SHS synergistically increased the risk of ADHD, evident as both inattention and hyperactivity/impulsivity.Conclusion:SHS, which is associated with hyperactivity/impulsivity in particular, combined with exposure to low blood levels of lead synergistically increased the risk of ADHD. Therefore, the exposure of children to both SHS and lead needs to be reduced.Implications:Although exposure to low levels of lead has been shown to be associated with ADHD, there is little evidence of symptom domain specificity. In our study, low blood lead levels were related to inattention. In addition, prenatal or postnatal exposure to SHS increased the risk of ADHD, particularly hyperactivity/impulsivity. Combined exposure to lead and SHS synergistically increased the risk for both these ADHD symptom domains. To protect children from environmental risk factors related to ADHD, it is necessary to further reduce children’s exposure to SHS and lead, even in those with low blood lead levels.

N-of-1 trials can be aggregated to generate group mean treatment effects: a systematic review and meta-analysis

ObjectivesTo evaluate how data from n-of-1 trials may be used in systematic reviews and meta-analyses by examining the effects of amphetamine and methylphenidate for attention-deficit hyperactivity disorder (ADHD). Study Design and SettingElectronic search of MEDLINE, EMBASE, and PsychINFO for English language articles published from 1950 to 2013. N-of-1 trials of pediatric participants with ADHD that assessed either amphetamine or methylphenidate vs. placebo were included. The primary outcome was improvement of core symptoms of ADHD, which was assessed by multiple rating scales. Studies with obtainable individual participant data were included in the meta-analysis. Weighted mean differences were computed using a random-effects model. ResultsNine studies were included in the amphetamine-placebo comparison and 10 in the methylphenidate-placebo comparison. Meta-analyses were consistently in favor of amphetamine in 10 of 11 ADHD symptom domains and methylphenidate in 7 of 12 symptom domains. A high degree of heterogeneity across participant treatment response was observed. ConclusionsMeta-analysis of n-of-1 trials suggests that amphetamine and methylphenidate are effective treatments for pediatric ADHD. Synthesizing n-of-1 trials enables assessment of individual responses to treatment as well as aggregate summaries across individuals and studies. It offers a promising general approach with applications across diverse treatments and disorders.

Genetic and Environmental Influences on the Developmental Course of Attention-Deficit/Hyperactivity Disorder Symptoms From Childhood to Adolescence

Attention-deficit/hyperactivity disorder (ADHD) is conceptualized as a neurodevelopmental disorder that is strongly heritable. However, to our knowledge, no study to date has examined the genetic and environmental influences explaining interindividual differences in the developmental course of ADHD symptoms from childhood to adolescence (ie, systematic decreases or increases with age). The reason ADHD symptoms persist in some children but decline in others is an important concern, with implications for prognosis and interventions. To assess the proportional impact of genes and the environment on interindividual differences in the developmental course of ADHD symptom domains of hyperactivity/impulsivity and inattention between ages 8 and 16 years. A prospective sample of 8395 twin pairs from the Twins Early Development Study, recruited from population records of births in England and Wales between January 1, 1994, and December 31, 1996. Data collection at age 8 years took place between November 2002 and November 2004; data collection at age 16 years took place between February 2011 and January 2013. Both DSM-IV ADHD symptom subscales were rated 4 times by participants' mothers. Estimates from latent growth curve models indicated that the developmental course of hyperactivity/impulsivity symptoms followed a sharp linear decrease (mean score of 6.0 at age 8 years to 2.9 at age 16 years). Interindividual differences in the linear change in hyperactivity/impulsivity were under strong additive genetic influences (81%; 95% CI, 73%-88%). More than half of the genetic variation was specific to the developmental course and not shared with the baseline level of hyperactivity/impulsivity. The linear decrease in inattention symptoms was less pronounced (mean score of 5.8 at age 8 years to 4.9 at age 16 years). Nonadditive genetic influences accounted for a substantial amount of variation in the developmental course of inattention symptoms (54%; 95% CI, 8%-76%), with more than half being specific to the developmental course. The large genetic influences on the developmental course of ADHD symptoms are mostly specific and independent of those that account for variation in the baseline level of symptoms. Different sets of genes may be associated with the developmental course vs the baseline level of ADHD symptoms and explain why some children remit from ADHD, whereas others persist. Recent longitudinal imaging data indicate that the maintenance or increase in symptoms is underpinned by atypical trajectories of cortical development. This may reflect a specific genetic liability, distinct from that which contributes to baseline ADHD symptoms, and warrants closer follow-up.

The Genetic Overlap of Attention-Deficit/Hyperactivity Disorder and Autistic-like Traits: an Investigation of Individual Symptom Scales and Cognitive markers.

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs) frequently co-occur. However, due to previous exclusionary diagnostic criteria, little is known about the underlying causes of this covariation. Twin studies assessing ADHD symptoms and autistic-like traits (ALTs) suggest substantial genetic overlap, but have largely failed to take into account the genetic heterogeneity of symptom subscales. This study aimed to clarify the phenotypic and genetic relations between ADHD and ASD by distinguishing between symptom subscales that characterise the two disorders. Moreover, we aimed to investigate whether ADHD-related cognitive impairments show a relationship with ALT symptom subscales; and whether potential shared cognitive impairments underlie the genetic risk shared between the ADHD and ALT symptoms. Multivariate structural equation modelling was conducted on a population-based sample of 1312 twins aged 7–10. Social-communication ALTs correlated moderately with both ADHD symptom domains (phenotypic correlations around 0.30) and showed substantial genetic overlap with both inattention and hyperactivity-impulsivity (genetic correlation = 0.52 and 0.44, respectively). In addition to previously reported associations with ADHD traits, reaction time variability (RTV) showed significant phenotypic (0.18) and genetic (0.32) association with social-communication ALTs. RTV captured a significant proportion (24 %) of the genetic influences shared between inattention and social-communication ALTs. Our findings suggest that social-communication ALTs underlie the previously observed phenotypic and genetic covariation between ALTs and ADHD symptoms. RTV is not specific to ADHD symptoms, but is also associated with social-communication ALTs and can, in part, contribute to an explanation of the co-occurrence of ASD and ADHD.

Relationship between white matter microstructure abnormalities and ADHD symptomatology in adolescents

The present study sought to evaluate whether white matter microstructure abnormalities observed in a cohort of adolescents with attention-deficit/hyperactivity disorder (ADHD) have specific relationships with either or both Hyperactivity/Impulsivity and Inattentive ADHD symptom domains that would support a dimensional view of ADHD as adopted in the DSM-V. Diffusion tensor imaging (DTI) data were acquired on 22 adolescents diagnosed with ADHD. Multiple regression analyses were performed to determine whether scalar DTI measures in 13 tracts-of-interest demonstrated meaningful associations with Hyperactivity/Impulsivity or Inattentive symptom severity. Fractional anisotropy and radial diffusivity measures of white matter integrity exhibited significant linear relationships with Hyperactivity/Impulsivity and Inattentive symptom severity. However, only radial diffusivity in the right superior longitudinal fasciculus was specifically linked to Inattentive symptom severity and not Hyperactivity/Impulsivity symptom severity. Our results provide preliminary evidence that symptom domains in ADHD are linked to neuroanatomical substrates and confirm the value in examining ADHD from a dimensional perspective.

Shared cognitive impairments and aetiology in ADHD symptoms and reading difficulties.

BackgroundTwin studies indicate that the frequent co-occurrence of attention deficit hyperactivity disorder (ADHD) symptoms and reading difficulties (RD) is largely due to shared genetic influences. Both disorders are associated with multiple cognitive impairments, but it remains unclear which cognitive impairments share the aetiological pathway, underlying the co-occurrence of the symptoms. We address this question using a sample of twins aged 7–10 and a range of cognitive measures previously associated with ADHD symptoms or RD.MethodsWe performed multivariate structural equation modelling analyses on parent and teacher ratings on the ADHD symptom domains of inattention and hyperactivity, parent ratings on RD, and cognitive data on response inhibition (commission errors, CE), reaction time variability (RTV), verbal short-term memory (STM), working memory (WM) and choice impulsivity, from a population sample of 1312 twins aged 7–10 years.ResultsThree cognitive processes showed significant phenotypic and genetic associations with both inattention symptoms and RD: RTV, verbal WM and STM. While STM captured only 11% of the shared genetic risk between inattention and RD, the estimates increased somewhat for WM (21%) and RTV (28%); yet most of the genetic sharing between inattention and RD remained unaccounted for in each case.ConclusionWhile response inhibition and choice impulsivity did not emerge as important cognitive processes underlying the co-occurrence between ADHD symptoms and RD, RTV and verbal memory processes separately showed significant phenotypic and genetic associations with both inattention symptoms and RD. Future studies employing longitudinal designs will be required to investigate the developmental pathways and direction of causality further.

Symptoms of autism and ADHD: a Swedish twin study examining their overlap.

Autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) show high comorbidity. The following questions were addressed regarding their specific symptoms: What is the factor structure of ASD and ADHD symptoms, to what degree do different symptom domains cluster together, to what extent are these domains caused by the same genetic and environmental influences, and what is the best model of their co-occurrence? A population-based twin cohort of over 17,000 9- and 12-year-olds were assessed using the Autism-Tics, AD/HD, and other Comorbidities parental interview inventory. Principal component analyses were conducted, and symptom domain clustering was assessed. Four multivariate twin models were compared. Factors split into three ASD (social impairments, communication impairments, and restricted repetitive behaviors and interests), and three ADHD (inattention, hyperactivity, and impulsivity) symptom domains. Some ASD-ADHD symptom domain combinations clustered together often, although others not at all. A two-factor common pathway model fit the data, suggesting that ASD and ADHD symptom domains tap into separate "ASD" and "ADHD" latent factors that showed high genetic overlap. All subdomains also showed significant specific genetic and environmental influences, reflecting the etiological heterogeneity both within and between ASD and ADHD. These findings support the conceptual distinction of ASD and ADHD, and demonstrate the considerable natural co-occurrence of particular ASD/ADHD symptom domains. The results imply that more children with 1 condition show features of the other condition than show complete comorbidity. Emphasis on symptom co-occurrence, rather than complete comorbidity between disorders, may help focus clinical approaches and advance molecular genetic research.

Candidate Genetic Pathways for Attention-Deficit/Hyperactivity Disorder (ADHD) Show Association to Hyperactive/Impulsive Symptoms in Children With ADHD

Because multiple genes with small effect sizes are assumed to play a role in attention-deficit/hyperactivity disorder (ADHD) etiology, considering multiple variants within the same analysis likely increases the total explained phenotypic variance, thereby boosting the power of genetic studies. This study investigated whether pathway-based analysis could bring scientists closer to unraveling the biology of ADHD. The pathway was described as a predefined gene selection based on a well-established database or literature data. Common genetic variants in pathways involved in dopamine/norepinephrine and serotonin neurotransmission and genes involved in neuritic outgrowth were investigated in cases from the International Multicentre ADHD Genetics (IMAGE) study. Multivariable analysis was performed to combine the effects of single genetic variants within the pathway genes. Phenotypes were DSM-IV symptom counts for inattention and hyperactivity/impulsivity (n = 871) and symptom severity measured with the Conners Parent (n = 930) and Teacher (n = 916) Rating Scales. Summing genetic effects of common genetic variants within the pathways showed a significant association with hyperactive/impulsive symptoms ((p)empirical = .007) but not with inattentive symptoms ((p)empirical = .73). Analysis of parent-rated Conners hyperactive/impulsive symptom scores validated this result ((p)empirical = .0018). Teacher-rated Conners scores were not associated. Post hoc analyses showed a significant contribution of all pathways to the hyperactive/impulsive symptom domain (dopamine/norepinephrine, (p)empirical = .0004; serotonin, (p)empirical = .0149; neuritic outgrowth, (p)empirical = .0452). The present analysis shows an association between common variants in 3 genetic pathways and the hyperactive/impulsive component of ADHD. This study demonstrates that pathway-based association analyses, using quantitative measurements of ADHD symptom domains, can increase the power of genetic analyses to identify biological risk factors involved in this disorder.

The Relationship Between ADHD Symptom Dimensions, Clinical Correlates, and Functional Impairments

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. 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. 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. 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.

The Separation of ADHD Inattention and Hyperactivity-Impulsivity Symptoms: Pathways from Genetic Effects to Cognitive Impairments and Symptoms

Both shared and unique genetic risk factors underlie the two symptom domains of attention deficit hyperactivity disorder (ADHD): inattention and hyperactivity-impulsivity. The developmental course and relationship to co-occurring disorders differs across the two symptom domains, highlighting the importance of their partially distinct etiologies. Familial cognitive impairment factors have been identified in ADHD, but whether they show specificity in relation to the two ADHD symptom domains remains poorly understood. We aimed to investigate whether different cognitive impairments are genetically linked to the ADHD symptom domains of inattention versus hyperactivity-impulsivity. We conducted multivariate genetic model fitting analyses on ADHD symptom scores and cognitive data, from go/no-go and fast tasks, collected on a population twin sample of 1,312 children aged 7-10. Reaction time variability (RTV) showed substantial genetic overlap with inattention, as observed in an additive genetic correlation of 0.64, compared to an additive genetic correlation of 0.31 with hyperactivity-impulsivity. Commission errors (CE) showed low additive genetic correlations with both hyperactivity-impulsivity and inattention (genetic correlations of 0.17 and 0.11, respectively). The additive genetic correlation between RTV and CE was also low and non-significant at -0.10, consistent with the etiological separation between the two indices of cognitive impairments. Overall, two key cognitive impairments phenotypically associated with ADHD symptoms, captured by RTV and CE, showed different genetic relationships to the two ADHD symptom domains. The findings extend a previous model of two familial cognitive impairment factors in combined subtype ADHD by separating pathways underlying inattention and hyperactivity-impulsivity symptoms.

Psychiatric comorbidity distribution and diversities in children and adolescents with attention deficit/hyperactivity disorder: a study from Turkey

ObjectiveWe aimed to determine distribution and diversities of psychiatric comorbidities in children and adolescents with attention deficit/hyperactivity disorder (ADHD) in terms of age groups, sex, and ADHD subtype.Materials and methodsThe sample included 6–18 year old children and adolescents from Turkey (N=108; 83 boys, 25 girls) diagnosed with ADHD. All comorbid diagnoses were determined based on the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version assessment.Results96.3% of the cases were found to have at least one psychiatric comorbid diagnosis. The most frequent psychiatric comorbid disorder was oppositional defiant disorder (69.4%) followed by anxiety disorders (49%) and elimination disorders (27.8%). Disruptive behavior disorders were more common in ADHD-combined type. Depression and anxiety disorders were more common in girls. Separation anxiety disorder and elimination disorder were more common in children, whereas depression, bipolar disorder, obsessive–compulsive disorder, and social phobia were more common in the adolescents.ConclusionAccording to our results, when a diagnostic tool was used to assess the presence of comorbid psychiatric disorders in children and adolescents diagnosed with ADHD, almost all cases had at least one comorbid diagnosis. Therefore, especially in the clinical sample, ADHD cases should not be solely interpreted with ADHD symptom domains, instead they should be investigated properly in terms of accompanying psychiatric disorders.

Increased Intrasubject Variability in Boys with ADHD Across Tests of Motor and Cognitive Control

Increased intrasubject variability (ISV), or short-term, within-person fluctuations in behavioral performance is consistently found in Attention-Deficit/Hyperactivity Disorder (ADHD). ADHD is also associated with impairments in motor control, particularly in boys. The results of the few studies that have examined variability in self-generated motor output in children with ADHD have been inconsistent. The current study examined variability in motor control during a finger sequencing task among boys with and without ADHD as well as the relationship between intrasubject variability during motor and cognitive control tasks. Changes in performance over the course of the task and associations with ADHD symptom domains were also examined to elucidate the nature of impaired motor control in children with ADHD. Fifty-one boys (ages 8 to 12years) participated in the study, including 28 boys with ADHD and 23 typically developing (TD) boys. Participants completed a finger sequencing task and a Go/No-Go task providing multiple measures of response speed and variability. Boys with ADHD were slower and more variable in both intertap interval on the finger sequencing task and reaction time on the Go/No-Go task, with measures of speed and variability correlated across the two tasks. For the entire cohort, the only unique predictor of parent ratings of hyperactive-impulsive symptoms was variability in intertap interval during finger sequencing, whereas inattentive symptoms were only predicted by reaction time variability on the Go/No-Go task. These findings suggest that inefficient motor control is implicated in the pathophysiology of ADHD, particularly in regards to developmentally inappropriate levels of hyperactivity and impulsivity.