Neurophysiological differences in inhibitory control between adults with ADHD and their peers

Inhibitory control allows individuals to suppress prepotent responses and resist irrelevant stimuli, and is thought to be a core deficit in Attention-deficit/hyperactivity disorder (ADHD). Whereas numerous studies have investigated neural mechanisms underlying inhibitory control deficits in children with ADHD, less is known about underlying mechanisms in young adults with ADHD. This study explores the neural correlates of inhibitory control in college students with ADHD—a population that, despite comparatively high educational attainment, still shows marked functional impairments in academic, social, and occupational functioning. Participants were 54 college students with ADHD and 29 typically developing peers. Specifically the fronto-centrally located N2 and the centro-parietal P3 event-related potential (ERP) components were hypothesized to show decreased amplitudes for the ADHD group due to their known association with inhibitory control. Dense array electroencephalography (EEG) data was collected during a Go/nogo task. Results show lower accuracy rates for the ADHD group and significant reductions in P3 amplitude as well as a trend for reduced N2 amplitude in nogo trials where subjects successfully inhibited a response. Notably, nogo N2 and P3 amplitudes correlated with the number of ADHD symptoms: namely, smaller amplitudes were associated with more symptoms. We conclude that when compared to their typically developing peers, relatively high functioning adults with ADHD still show a deviant neural signature. These results contribute to the growing literature of adult ADHD and increase our understanding of the neural correlates of inhibitory control associated with ADHD.     

Physiological and psychological stress responses in adults with attention-deficit/hyperactivity disorder (ADHD)

According to self-report and unsystematic observational data adult patients with attention-deficit/hyperactivity disorder suffer from increased vulnerability to daily life stressors. The present study examined psychological and physiological stress responses in adult ADHD subjects in comparison to healthy controls under laboratory conditions. Thirty-six subjects (18 patients with DSM-IV ADHD diagnosis, 18 sex- and age-matched healthy controls) underwent the Trier Social Stress Test (TSST; Kirschbaum, C., Pirke, K.-M., Hellhammer, D.H., 1993. The “Trier Social Stress Test”—a tool for investigating psychobiological stress responses in a laboratory setting. Neuropsychobiology 28, 76–81), a standardized psychosocial stress protocol which contains a stress anticipation phase and a stress phase with a free speech assignment and subsequent performance of a mental arithmetic. Physiological stress measures were salivary cortisol as an indicator of the HPA axis, heart rate (HR), and time- and frequency-domain heart rate variability (HRV) parameters. Subjective stress experience was measured via self-report repeatedly throughout the experimental session. In line with previous theoretical and empirical work in the field of childhood ADHD, it was hypothesized that the ADHD and control group would exhibit comparable baseline levels in all dependent variables. For ADHD subjects, we expected attenuated responses of the physiological parameters during anticipation and presence of the standardized stressor, but elevated subjective stress ratings. Hypotheses were confirmed for the baseline condition. Consistent with our assumptions in regard to the psychological stress response, the ADHD group experienced significantly greater subjective stress. The results for the physiological variables were mixed.

While ADHD subjects revealed an attenuated HR during the stress phase, no significant group differences were found for the other parameters, although a trend was observed for both the low frequency/high frequency (LF/HF) ratio of the HRV power spectral analysis and salivary cortisol (the latter possibly indicating generally lower cortisol levels in ADHD subjects). In summary, the present findings are the first to demonstrate a significant alteration of a specific physiological stress measure (HR) and, more clearly, of psychological aspects of the stress response in adults suffering from ADHD. In regard to the physiological stress response, it is recommended that future studies employ larger sample sizes and a more comprehensive range of physiological stress parameters. Additionally, the issue of transferability of laboratory results to real life stressors needs to be addressed.     

Anxiety relates to classroom executive function problems in students with ASD,but not ADHD

BackgroundAnxiety occurs at elevated rates in developmental disorders and has been linked to executive functioning (EF) deficits. EF is strongly related to academic outcomes, but the relationship between anxiety and EF in the classroom has not been examined.MethodWe explored this relationship in two neurodevelopmental disorders, autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD), in order to evaluate the specificity of associations between parent-reported anxiety and teacher-reported EF deficits in the classroom setting.ResultsGreater anxiety was associated with more classroom EF-related problems in the ASD group, but not in the ADHD group. Item-level analysis of classroom EF problems in the ASD group revealed associations between anxiety and difficulties with task initiation, attention, and completion. Anxiety was not related to total or item-level teacher-reported EF problems in the ADHD group.ConclusionFurther investigation into disorder-specific mechanisms that lead to the manifestation of anxiety symptoms may pave the way for more effective treatment and favorable academic outcome. Anxiety is related to poor EF in the classroom for students with ASD, which has implications for treating anxiety to promote positive academic outcomes and incorporating EF supports and training into treatment models for anxiety. The lack of association between anxiety and EF for students with ADHD was unexpected and warrants further exploration.     

Autism spectrum disorder symptoms in children with ADHD: A community-based study

This study examined the prevalence of autism spectrum disorder (ASD) symptoms in a community-based sample of children with attention-deficit/hyperactivity disorder (ADHD) and non-ADHD controls. We also examined the relationship between ASD symptoms and ADHD subtype, ADHD symptom severity and child gender. Participants were 6–10-year-old children (164 ADHD; 198 non-ADHD control) attending 43 schools in Melbourne, Australia, who were participating in the Children's Attention Project. ADHD was assessed in two stages using the parent and teacher Conners’ 3 ADHD index and the Diagnostic Interview Schedule for Children IV (DISC-IV). ASD symptoms were identified using the Social Communication Questionnaire (SCQ). Unadjusted and adjusted linear and logistic regression examined continuous and categorical outcomes, respectively. Children with ADHD had more ASD symptoms than non-ADHD controls (adjusted mean difference = 4.0, 95% confidence interval (CI) 2.8; 5.3, p < 0.001, effect size = 0.7). Boys with ADHD had greater ASD symptom severity than girls with ADHD (adjusted mean difference = 2.9, 95% CI 0.8; 5.2, p = 0.01, effect size = 0.4). Greater ADHD symptom severity was associated with greater ASD symptom severity (regression co-efficient = 1.6, 95% CI 1.2; 2.0, p < 0.001). No differences were observed by ADHD subtype. Greater hyperactive/impulsive symptoms were associated with greater ASD symptoms (regression coefficient = 1.0; 95% CI 0.0; 2.0, p = 0.04) however, this finding attenuated in adjusted analyses (p = 0.45). ASD symptoms are common in children with ADHD. It is important for clinicians to assess for ASD symptoms to ensure appropriate intervention.     

Rates of comorbid symptoms in children with ASD,ADHD, and comorbid ASD and ADHD

The current diagnostic criteria do not allow co-diagnosis of autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). As a result, there has been little research on how these two disorders co-occur in the ASD population. The current study aimed to extend the literature in this area by examining comorbid rates in three different diagnostic groups (ASD, ADHD, and comorbid ASD + ADHD) using the Autism Spectrum Disorders-Comorbidity for Children (ASD-CC). Children with comorbid ASD and ADHD evinced higher rates of comorbid symptoms than children with ASD or ADHD alone. Additionally, children with comorbid ASD and ADHD endorsed more severe comorbid symptoms. Implications regarding these findings are discussed.     

A comparison of tantrum behavior profiles in children with ASD,ADHD and comorbid ASD and ADHD

The present study was conducted to compare rates of tantrum behaviors in children with autism spectrum disorders (ASD) (n = 255), attention-deficit/hyperactivity disorder (ADHD) (n = 40) and children with comorbid ASD and ADHD (n = 47). Parents/guardians of children aged 3–16 years were surveyed about their children's behaviors using the Autism Spectrum Disorders-Comorbidity for Children (ASD-C-C). Children with ADHD alone differed from children with ASD alone and children with comorbid ASD and ADHD on rates of tantrum behaviors. Examination of individual tantrum behavior items indicated that children with comorbid ASD and ADHD have a more similar symptom presentation to children with ASD than children with ADHD. This study adds to the literature on the presentation of common co-occurring behaviors of ASD when there is comorbid ADHD. The implications of these findings may aid in the assessment and treatment of tantrum behaviors in children with comorbid ASD and ADHD.     

Validation of DSM-5 age-of-onset criterion of attention deficit/hyperactivity disorder (ADHD) in adults: Comparison of life quality,functional impairment,and family function

The newly published Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) elevates the threshold of the ADHD age-of-onset criterion from 7 to 12 years. This study evaluated the quality of life and functional impairment of adults with ADHD who had symptoms onset by or after 7 years and examined the mediation effect of family function and anxiety/depression symptoms between ADHD diagnosis and quality of life and functional impairment. We assessed 189 adults with ADHD and 153 non-ADHD controls by psychiatric interview and self-administered reports on the Adult ADHD Quality of Life Scale, Weiss Functional Impairment Rating Scale, Family APGAR, and Adult Self Report Inventory-4. The ADHD group was divided into early-onset ADHD (onset <7 years, n = 147) and late-onset ADHD (onset between 7 and 12 years, n = 42). The mediation analysis was conducted to verify the mediating factors from ADHD to functional impairment and quality of life. The late-onset ADHD had more severe functional impairment at work and poorer family support than early-onset ADHD while they had comparable impairment at other domains. Less perceived family support and current anxiety/depressive symptoms partially mediated the link between ADHD diagnosis and quality of life/functional impairment both in early- and late-onset ADHD. Our data support decreased quality of life and increased functional impairment in adult ADHD, regardless of age of onset, and these adverse outcomes may be mediated by family support and anxiety/depression at adulthood. Our findings also imply that the new DSM-5 ADHD criteria do not over-include individuals without impairment.     

ADHD and autistic traits,family function,parenting style,and social adjustment for Internet addiction among children and adolescents in Taiwan: A longitudinal study

This longitudinal study investigated the prevalence, predictors, and related factors for Internet addiction among elementary and junior high school students in Taiwan. A convenient sample of grades 3, 5, and 8 students (n = 1153) was recruited from six elementary and one junior high schools. They were assessed during the beginning and the end of the spring semester of 2013. Internet addiction was examined by the Chen Internet Addiction Scale (CIAS). Other factors were screened using the Chinese version of the Autism Spectrum Quotient (AQ) for autistic trait, the Parental Bonding Instrument (PBI) for parenting, the Family APGAR for family support, the Social Adjustment Inventory for Children and Adolescents for social function, and the Swanson, Nolan, and Pelham, version IV scale (SNAP-IV) for ADHD symptoms. The prevalence of Internet addiction decreased from 11.4% to 10.6%. Male, low family support, poor social adjustment, and high ADHD-related symptoms were related to Internet addiction. However, there was an inverse relationship between autistic traits and Internet addiction. Further, its predictivity could be accounted by poor academic performance, male, and protective parenting style. Internet addiction is not uncommon among youths in Taiwan. The predictors identified in this study could be the specific measures for the development of a prevention program for Internet addiction in the youth population.     

ADHD 24/7: Circadian clock genes,chronotherapy and sleep/wake cycle insufficiencies in ADHD

Abstract

Objectives: The current paper addresses the evidence for circadian clock characteristics associated with attention-deficit hyperactivity disorder (ADHD), and possible therapeutic approaches based on chronomodulation through bright light (BL) therapy.

Methods: We review the data reported in ADHD on genetic risk factors for phase-delayed circadian rhythms and on the role of photic input in circadian re-alignment.

Results: Single nucleotide polymorphisms in circadian genes were recently associated with core ADHD symptoms, increased evening-orientation and frequent sleep problems. Additionally, alterations in exposure and response to photic input may underlie circadian problems in ADHD. BL therapy was shown to be effective for re-alignment of circadian physiology toward morningness, reducing sleep disturbances and bringing overall improvement in ADHD symptoms. The susceptibility of the circadian system to phase shift by timed BL exposure may have broad cost-effective potential implications for the treatment of ADHD.

Conclusions: We conclude that further research of circadian function in ADHD should focus on detection of genetic markers (e.g., using human skin fibroblasts) and development of BL-based therapeutic interventions.     

Hyperactivity in boys with attention-deficit/hyperactivity disorder (ADHD): The role of executive and non-executive functions

Motor activity of boys (age 8–12 years) with (n = 19) and without (n = 18) ADHD was objectively measured with actigraphy across experimental conditions that varied with regard to demands on executive functions. Activity exhibited during two n-back (1-back, 2-back) working memory tasks was compared to activity during a choice-reaction time (CRT) task that placed relatively fewer demands on executive processes and during a simple reaction time (SRT) task that required mostly automatic processing with minimal executive demands. Results indicated that children in the ADHD group exhibited greater activity compared to children in the non-ADHD group. Further, both groups exhibited the greatest activity during conditions with high working memory demands, followed by the reaction time and control task conditions, respectively. The findings indicate that large-magnitude increases in motor activity are predominantly associated with increased demands on working memory, though demands on non-executive processes are sufficient to elicit small to moderate increases in motor activity as well.     

Neuropsychological assessment of attention in adults with different subtypes of attention-deficit/hyperactivity disorder

Summary There is only little information about varying attention functions of adults with different DSM-IV subtypes of attention-deficit/hyperactivity disorder (ADHD). In the present study groups of adult patients with ADHD – predominantly inattentive type, ADHD – predominantly hyperactive-impulsive type or ADHD – combined type and three healthy control groups were compared regarding multiple components of attention. Assessment of attention was performed using a computerized neuropsychological test battery for attentional functions. In comparison with healthy subjects, the three patient groups displayed impairments of vigilance, selective attention, divided attention, and flexibility. These impairments of attention of ADHD subgroups were primarily observed with regard to reaction time. With regard to tonic and phasic alertness no differences between patient and control groups could be found. Comparison between ADHD subgroups revealed that DSM-IV subtypes of ADHD differ in measures of divided attention, selective attention and flexibility. Differences between ADHD subgroups were primarily observed with regard to task accuracy. The results suggest that while distinct profiles of attentional functioning were observed between adult patients with ADHD and healthy adults indicating gross disturbances of various attention functions in patients with ADHD, differences between ADHD subgroups were only weak. Correspondence: Oliver Tucha, School of Psychology, University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA, UK     

The Impact of Depressive Symptoms in Adults with ADHD Symptoms on Family Function and ADHD Symptoms of Their Children

Objective

People with attention-deficit/hyperactivity disorder (ADHD) exhibit considerable impairment in social, academic, or occupational functioning. The present study aimed to examine the patterns of associations between ADHD symptoms, depression, and family functioning.

Methods

The sample consisted of 1,022 adults randomly selected from a district in Seoul, South Korea. Several self-assessment scales were utilized to rate ADHD symptoms (both past and current), current symptoms of depression, and level of family functioning. ADHD symptoms in the children of these participants were also assessed. Pearson''s correlation and multiple linear regression analyses were performed; structural equation modeling (SEM) was conducted to determine the best fitting model.

Results

Adult ADHD symptoms were positively associated with depressive symptoms. Depressive symptoms, in turn, mediated the relationship between adult ADHD symptoms and cohesion among family members. In addition, depressive symptoms mediated the relationship between adult ADHD symptoms and their children''s ADHD symptoms.

Conclusion

The relationship between adult ADHD symptoms and family dysfunction may be influenced by depressive symptoms. When treating ADHD in adults, clinicians should pay attention to the presence or absence of depression.     

Executive functioning in children with ASD + ADHD and ASD + ID: A systematic review

Executive functions (EF) are skills that impact an individual’s ability to flexibly and efficiently problem solve and react to their environment. Children with neurodevelopmental disorders (NDDs), such as autism spectrum disorder (ASD), commonly experience EF deficits. However, it is unclear how a co-occurring diagnosis of attention-deficit/hyperactivity disorder (ADHD) or intellectual disability (ID) impact EF in children with ASD. This study systematically reviewed 26 studies – within 24 journal articles – that examined EF among children with ASD + ADHD and ASD + ID. Results revealed many non-congruent findings regarding EF in children with ASD + ADHD and ASD + ID, including differences across performance-based and indirect measures of EF. Children with ASD + ADHD exhibited unique flexibility and shifting, inhibition, and attention deficits. Among children with ASD + ID, planning and organizing, flexibility and shifting, attention, behavior regulation, and global EF skills significantly differed from comparison groups. Notably, these findings were dependent on assessment type used (performance-based versus indirect). Furthermore, analyses of mean Z-scores suggest that children with ASD + ADHD and ASD + ID exhibited more severe EF impairments than children with ASD. These results may be used to inform assessment practices for differentiating and determining co-occurring diagnoses. Understanding unique EF deficits may also inform the development of targeted treatment and interventions.     

Prediction of childhood ADHD symptoms to quality of life in young adults: Adult ADHD and anxiety/depression as mediators

Childhood attention-deficit/hyperactivity disorder (ADHD) symptoms may persist, co-occur with anxiety and depression (ANX/DEP), and influence quality of life (QoL) in later life. However, the information about whether these persistent ADHD and ANX/DEP mediate the influence of childhood ADHD on adverse QoL in adulthood is lacking. This study aimed to determine whether adult ADHD symptoms and/or ANX/DEP mediated the association between childhood ADHD and QoL. We assessed 1382 young men aged 19–30 years in Taiwan using self-administered questionnaires for retrospective recall of ADHD symptoms at ages 6–12, and assessment of current ADHD and ANX/DEP symptoms, and QoL. We conducted mediation analyses and compared the values of mediation ratio (P_M) by adding mediators (adult ADHD and ANX/DEP), individually and simultaneously into a regression model with childhood ADHD as an independent variable and QoL as a dependent variable. Our results showed that both adult ADHD and ANX/DEP symptoms significantly mediated the association between childhood ADHD and QoL (P_M = 0.71 for ANX/DEP, P_M = 0.78 for adult ADHD symptoms, and P_M = 0.91 for both). The significance of negative correlations between childhood ADHD and four domains of adult QoL disappeared after adding these two mediators in the model. Our findings suggested that the strong relationship between childhood ADHD and adult life quality can be explained by the presence of persistent ADHD symptoms and co-occurring ANX/DEP. These two mediators are recommended to be included in the assessment and intervention for ADHD to offset the potential adverse life quality outcome in ADHD.     

Molecular genetic studies of ADHD and its candidate genes: A review

Attention-deficit/hyperactivity disorder (ADHD) is a common childhood-onset psychiatric disorder with high heritability. In recent years, numerous molecular genetic studies have been published to investigate susceptibility loci for ADHD. These results brought valuable candidates for further research, but they also presented great challenge for profound understanding of genetic data and general patterns of current molecular genetic studies of ADHD since they are scattered and heterogeneous. In this review, we presented a retrospective review of more than 300 molecular genetic studies for ADHD from two aspects: (1) the main achievements of various studies were summarized, including linkage studies, candidate-gene association studies, genome-wide association studies and genome-wide copy number variation studies, with a special focus on general patterns of study design and common sample features; (2) candidate genes for ADHD have been systematically evaluated in three ways for better utilization. The thorough summary of the achievements from various studies will provide an overview of the research status of molecular genetics studies for ADHD. Meanwhile, the analysis of general patterns and sample characteristics on the basis of these studies, as well as the integrative review of candidate ADHD genes, will propose new clues and directions for future experiment design.     

Psychometric properties of Japanese version of the Swanson,Nolan, and Pelham,version-IV Scale-Teacher Form: A study of school children in community samples

Background: Psychometric properties of The Japanese version of Swanson, Nolan, and Pelham IV scale (SNAP-IV)-Teacher Form were examined in this study. Method: Community samples of 1296 children (Grade 1–9, boys 52.9%) were collected from public elementary/middle schools in suburban areas. Teachers rated their children’s behavior using Japanese version of SNAP-IV-Teacher Form and Strength and Difficulties Questionnaire (SDQ). Results: A three-factor structure model, which was equivalent with AD/HD symptoms subscales (inattention, hyperactivity/impulsivity) and oppositional-defiant disorder symptoms subscale was obtained and confirmed in an explorative/confirmative factorial analysis (Goodness-of-Fit Index = 0.913, Comparative Fit Index = 0.959, root mean square error of approximation = 0.056). The current version of the SNAP-IV-Teacher Form demonstrated good test–retest reliability (intra-class correlation = 0.752–0.822), high internal consistency (Cronbach’s α = 0.933–0.952), significant correlations with relevant subscales of Japanese version of SDQ, and typical effects of age and gender on those subscales. Conclusion: The current study indicates that the Japanese version of SNAP-IV-Teacher Form is a reliable and valid instrument for rating symptoms related to AD/HD and ODD.