ADHD latent class clusters: DSM-IV subtypes and comorbidity

Stimulant medications in children with ADHD normalize the structure of brain regions associated with attention and reward

Children with ADHD show abnormal brain function and structure. Neuroimaging studies found that stimulant medications may improve brain structural abnormalities in children with ADHD. However, prior studies on this topic were conducted with relatively small sample sizes and wide age ranges and showed inconsistent results. In this cross-sectional study, we employed latent class analysis and linear mixed-effects models to estimate the impact of stimulant medications using demographic, clinical measures, and brain structure in a large and diverse sample of children aged 9-11 from the Adolescent Brain and Cognitive Development Study. We studied 273 children with low ADHD symptoms and received stimulant medication (Stim Low-ADHD), 1002 children with high ADHD symptoms and received no medications (No-Med ADHD), and 5378 typically developing controls (TDC). After controlling for the covariates, compared to Stim Low-ADHD and TDC, No-Med ADHD showed lower cortical thickness in the right insula (INS, d = 0.340, PFDR = 0.003) and subcortical volume in the left nucleus accumbens (NAc, d = 0.371, PFDR = 0.003), indicating that high ADHD symptoms were associated with structural abnormalities in these brain regions. In addition, there was no difference in brain structural measures between Stim Low-ADHD and TDC children, suggesting that the stimulant effects improved both ADHD symptoms and ADHD-associated brain structural abnormalities. These findings together suggested that children with ADHD appear to have structural abnormalities in brain regions associated with saliency and reward processing, and treatment with stimulant medications not only improve the ADHD symptoms but also normalized these brain structural abnormalities.

Is There a Deficit in Product and Process of Handwriting in Children with Attention Deficit Hyperactivity Disorder? A Systematic Review and Recommendations for Future Research

Handwriting abnormalities in children with attention deficit hyperactivity disorder (ADHD) have sometimes been reported both (i) at the product level (i.e., quality/legibility of the written trace and speed of writing) and (ii) at the process level (i.e., dynamic and kinematic features, such as on-paper and in-air durations, pen pressure and velocity peaks, etc.). Conversely, other works have failed to reveal any differences between ADHD and typically developing children. The question of the presence and nature of handwriting deficits in ADHD remains open and merits an in-depth examination. The aim of this systematic review was, therefore, to identify studies that have investigated the product and/or process of handwriting in children with ADHD compared to typically developing individuals. This review was conducted and reported in accordance with the PRISMA statement. A literature search was carried out using three electronic databases. The methodological quality of the studies was systematically assessed using the Critical Appraisal Skills Program (CASP) criteria. Twenty-one articles were identified. Of these, 17 described handwriting quality/legibility, 12 focused on speed and 14 analyzed the handwriting process. All the studies (100%) with satisfactory methodology procedures reported an impaired product and process in children with ADHD, while 25% evidenced a difference in the speed of production. Most importantly, the studies differed widely in their methodological approaches. Substantial gaps remain, particularly with regard to ascertaining comorbidities, ADHD subtypes and the medical status of the included children. The lack of overall homogeneity in the samples calls for higher quality studies. We conclude with recommendations for further studies.

Temperamental and psychomotor predictors of ADHD symptoms in children born after a threatened preterm labour: a 6-year follow-up study

Children born after threatened preterm labour (TPL), regardless of whether it ends in preterm birth, may represent an undescribed "ADHD cluster". The aim of this cohort study is to identify early temperament and psychomotor manifestations and risk factors of TPL children who present ADHD symptoms. One hundred and seventeen mother-child pairs were followed from TPL diagnosis until the child's 6 years of life. TPL children were divided according to the prematurity status into three groups: full-term TPL (n = 26), late-preterm TPL (n = 53), and very-preterm TPL (n = 38). A non-TPL group (n = 50) served as control. Temperament and psychomotor development at age 6 months and ADHD symptoms at age 6 years were assessed. Perinatal and psychosocial factors were also recorded. All TPL groups showed higher severity of ADHD symptoms compared with non-TPL children (difference in means + 4.19 for the full-term group, + 3.64 for the late-preterm group, and  + 4.99 for the very-preterm group, all ps < 0.021). Concretely, very-preterm and late-preterm TPL children showed higher restless/impulsive behaviours, whereas full-term TPL children showed higher emotional lability behaviours. Higher surgency/extraversion and delayed fine motor skills at age 6 months predicted ADHD symptoms at 6 years in TPL children. Male sex, maternal state anxiety symptoms at TPL diagnosis, low parental education, and past maternal experience of traumatic events predicted higher ADHD symptoms in TPL children. Therefore, TPL children may have a higher risk for developing ADHD symptoms, presenting a phenotype that depends on the prematurity status. Moreover, the specific combination of early manifestations and risk factors suggests that TPL children may conform an undescribed group at-risk of ADHD symptoms.

Classifying Young Children with Attention-Deficit/Hyperactivity Disorder Based on Child, Parent, and Family Characteristics: A Cross-Validation Study

We aimed to identify subgroups of young children with differential risks for ADHD, and cross-validate these subgroups with an independent sample of children. All children in Study 1 (N = 120) underwent psychological assessments and were diagnosed with ADHD before age 7. Latent class analysis (LCA) classified children into risk subgroups. Study 2 (N = 168) included an independent sample of children under age 7. A predictive model from Study 1 was applied to Study 2. The latent class analyses in Study 1 indicated preference of a 3-class solution (BIC = 3807.70, p < 0.001). Maternal education, income-to-needs ratio, and family history of psychopathology, defined class membership more strongly than child factors. An almost identical LCA structure from Study 1 was replicated in Study 2 (BIC = 5108.01, p < 0.001). Indices of sensitivity (0.913, 95% C.I. 0.814−0.964) and specificity (0.788, 95% C.I. 0.692−0.861) were high across studies. It is concluded that the classifications represent valid combinations of child, parent, and family characteristics that are predictive of ADHD in young children.

Latent Structure of Combined Autistic and ADHD Symptoms in Clinical and General Population Samples: A Scoping Review

Background: Many phenotypic studies have estimated the degree of comorbidity between Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD), but few have examined the latent, or unobserved, structure of combined ASD and ADHD symptoms. This is an important perquisite toward better understanding the overlap between ASD and ADHD. Methods: We conducted a scoping review of studies that examined the factor or latent class structure of ASD and ADHD symptoms within the same clinical or general population sample. Results: Eight studies met final inclusion criteria. Four factor analysis studies found that ASD and ADHD domains loaded separately and one found that some ASD and ADHD domains loaded together. In the three latent class studies, there were evidence of profiles with high levels of co-occurring ASD and ADHD symptoms. Conclusions: Our scoping review provides some evidence of phenotypic overlap between ASD and ADHD at the latent, or unobserved, level, particularly when using a "person-centered" (latent class analysis) vs. a "variable-centered" (factor analysis) approach.

Presenting problem profiles for adolescents with ADHD: differences by sex, age, race, and family adversity

BACKGROUND

Adolescents with attention-deficit/hyperactivity disorder (ADHD) experience developmentally distinct challenges from children and adults with ADHD. Yet no work in this age group identifies treatment-related phenotypes that can inform treatment matching, development of tailored treatments, and screening efforts.

METHOD

This study uses Latent Profile Analysis to detect unique presenting problem profiles among adolescents with ADHD and to test whether these profiles differ by key individual characteristics (age, sex, race, family adversity level). Participants were 854 ethnically diverse adolescents (ages 10-17) from the ADHD Teen Integrative Data Analysis Longitudinal (TIDAL) dataset who were assessed at clinical referral. Parent, adolescent, and teacher ratings, educational testing, and school records measured eight key presenting problems at intake.

RESULTS

A three-profile solution emerged. ADHD simplex (63.7%) was characterized by a mix of the ADHD-Inattentive and ADHD-Combined subtypes, moderate impairment levels, and infrequent comorbidities. ADHD + internalizing (11.4%) was characterized by higher likelihood of comorbid anxiety and/or depression. The disruptive/disorganized ADHD (24.9%) profile was characterized by severe organization, time management, and planning (OTP) problems, the ADHD-Combined subtype, and frequent disruptive behavior at school. Age did not vary across these phenotypes. More females were present in the ADHD + internalizing phenotype; males were more likely to be found in the disruptive/disorganized ADHD phenotype. Higher family adversity and African American race were associated with the disruptive/disorganized ADHD phenotype.

CONCLUSIONS

Adolescents with ADHD demonstrate varying presenting problem phenotypes that vary by sex, family adversity, and race/ethnicity. Consideration of these phenotypes may inform treatment matching and efforts to improve screening among under-diagnosed groups.

Early Development of Comorbidity Between Symptoms of ADHD and Anxiety

Attention-deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that shares a high comorbidity with anxiety disorders. However, the early development of comorbid ADHD and anxiety symptoms is not well-understood. In this study, the bidirectional relation between ADHD and anxiety symptoms was examined by testing two models of the development of ADHD and anxiety comorbidity: an anxiety effects model, which posits that anxiety symptoms contribute to the development of ADHD symptoms, and an ADHD effects model, which posits that ADHD symptoms contribute to the development of anxiety symptoms. Within the ADHD effects model, parenting practices were tested as mediators of this relation. Participants included children who were 3 years old at baseline (n = 258) and their caregivers who reported on their children's ADHD and anxiety symptoms annually for 3 years. The bidirectional relation of parent-reported anxiety and ADHD symptoms was tested using a series of cross-lagged models. Results indicated that ADHD symptoms predicted later anxiety symptoms, but anxiety symptoms did not predict later ADHD symptoms. Parenting practices did not mediate the relation between ADHD and anxiety symptoms within the ADHD effects model. These findings suggest that ADHD-anxiety comorbidity may develop in part because early symptoms of ADHD contribute to the development of anxiety symptoms; future research should be conducted to elucidate the mechanisms of this relation.

Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive Subtype/Presentation: Research Progress and Translational Studies

Research on the predominantly inattentive attention-deficit/hyperactivity disorder (ADHD-PI) subtype/presentation is important given its high prevalence, but paradoxically it is under-recognized and undertreated. The temporal stability of the inattention symptom could impact the high worldwide prevalence of ADHD-PI. Some evidence suggests differences in the nature of attentional deficit in ADHD-PI vs. that in other subtypes. Impairments in neuropsychological, neurocognitive, and social functioning are also evident in ADHD-PI, which could be specific to the subtype (e.g., processing speed, social perception, and skills), or differ from others in severity. Neuroimaging studies have also revealed ADHD-PI-specific neuropathological abnormalities and those that are shared with other subtypes. ADHD-PI is highly comorbid with learning and internalizing (e.g., anxiety and depression) disorders. There is no solid evidence for ADHD-PI-specific genetic etiologies and differential responses of subtypes to ADHD medications. Translational studies have used the Wistar Kyoto/NCrl substrain which requires further characterizations as an ADHD-PI model. Overall, ADHD-PI research has been conducted in the context of the Diagnostic and Statistical Manual, which arguably does not conform to the widely recognized "dimensional" view of ADHD. The Research Domain Criteria has been proposed to provide a novel framework for understanding the nature of neuropsychiatric illnesses and ultimately improve their diagnosis and treatment.

Patterns and Predictors of Service Utilization Among Youth With ADHD-Predominantly Inattentive Presentation

Objective: This study examined rates and predictors of educational and mental health service utilization among youth with ADHD-predominantly inattentive presentation (ADHD-I). Method: Participants were 199 children with ADHD-I in Grades 2 to 5. Parents reported past-year child service utilization. Parents and teachers rated child ADHD and oppositional defiant disorder (ODD) symptom severity and functional impairment. Children completed an academic achievement test. Results: All children had impairment at school and home. Most received some sort of school service (79%), but only 23% received community-based services. ADHD symptom severity was unrelated to service utilization. However, higher parent-rated functional impairment predicted community service utilization. Academic underachievement and higher teacher-rated functional impairment predicted school service utilization. Conclusion: Many youth with ADHD-I experience impairment across domains without receiving adequate services for these problems. Functional impairment appears to be a stronger predictor of service utilization than ADHD symptom severity, demonstrating the importance of impairment in understanding service needs for ADHD-I.

Do we need an irritable subtype of ADHD? Replication and extension of a promising temperament profile approach to ADHD subtyping

Attention deficit hyperactivity disorder (ADHD) is emblematic of unresolved heterogeneity in psychiatric disorders-the variation in biological, clinical, and psychological correlates that impedes progress on etiology. One approach to this problem is to characterize subgroups using measures rooted in biological or psychological theory, consistent with the National Institute of Mental Health's research domain criteria initiative. Within ADHD, a promising application involves using emotion trait profiles that can address the role of irritability as a complicating feature for ADHD. Here, a new sample of 186 children with ADHD was evaluated using community detection analysis to determine if meaningful subprofiles existed and if they replicated those previously identified. The new sample and a prior sample were pooled for evaluation of (a) method dependence, (b) longitudinal assessment of the stability of classifications, and (c) clinical prediction 2 years later. Three temperament profiles were confirmed within the ADHD group: one with normative emotional functioning ("mild"), one with high surgency ("surgent"), and one with high negative affect ("irritable"). Profiles were similar across statistical clustering approaches. The irritable group had the highest external validity: It was moderately stable over time and it enhanced prospective prediction of clinical outcomes beyond standard baseline indicators. The irritable group was not reducible to ADHD + oppositional defiant disorder, ADHD + disruptive mood dysregulation disorder, or other patterns of comorbidity. Among the negative affect domains studied, trait proneness to anger uniquely contributed to clinical prediction. Results extend our understanding of chronic irritability in psychiatric disorders and provide prospects for a fresh approach to assessing ADHD heterogeneity focused on the distinction between ADHD with and without anger/irritability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Evaluating relationships among clinical working memory assessment and inattentive and hyperactive/impulsive behaviors in a community sample of children

OBJECTIVE

This study examined relationships between inattentive and hyperactive/impulsive behaviors and working memory (WM) functioning, and the utility of WM in categorical diagnosis of ADHD versus considering ADHD symptoms on a continuum.

METHOD

The study included 50 male children (6-12 years). Inattentive and hyperactive/impulsive behaviors were measured by the Conners-3P parent report, and WM was assessed by the WISC-IV WM subtests and Working Memory Index (WMI).

RESULTS

WISC-IV Arithmetic and Digit Span Backward were most consistently related to inattentive behaviors, and no WM measure was consistently related to ADHD hyperactive/impulsive behaviors. Arithmetic and Digit Span Backward also accounted for significant variance in inattentive behaviors and ADHD inattention symptoms, respectively. Neither the WMI nor the Arithmetic subtest correctly classified individuals diagnosed with ADHD.

CONCLUSION

Measurement of inattentive behaviors on a continuum best characterized relationships between symptoms of ADHD and WM functioning; WM functioning did not have utility in categorical understanding of ADHD.

Academic and Social Functioning Associated with Attention-Deficit/Hyperactivity Disorder: Latent Class Analyses of Trajectories from Kindergarten to Fifth Grade

Children with attention-deficit/hyperactivity disorder (ADHD) are known to exhibit significantly lower academic and social functioning than other children. Yet the field currently lacks knowledge about specific impairment trajectories experienced by children with ADHD, which may constrain early screening and intervention effectiveness. Data were analyzed from a nationally representative U.S. cohort in the Early Childhood Longitudinal Study, Kindergarten Class of 1998-1999 (ECLS-K) for 590 children (72.7 % male) whose parents reported a formal diagnosis of ADHD. Children's math, reading, and interpersonal skills were assessed at 5 time points between kindergarten and fifth grade. Growth mixture model analyses indicated 4 latent trajectory classes for reading, 8 classes for math, and 4 classes for interpersonal skills. Membership in reading and math trajectory classes was strongly related; overlaps with interpersonal skills classes were weaker. Trajectory class membership was correlated with demographic characteristics and behavioral functioning. Children with ADHD display substantial heterogeneity in their reading, math, and interpersonal growth trajectories, with some groups of children especially likely to display relatively severe levels of academic and social impairment over time. Early screening and intervention to address impairment, particularly reading difficulties, among kindergarten students with ADHD is warranted.

Cluster Individuals Based on Phenotype and Determine the Risk for Atrial Fibrillation in the PREVEND and Framingham Heart Study Populations

Background

Risk prediction of atrial fibrillation (AF) is of importance to improve the early diagnosis and treatment of AF. Latent class analysis takes into account the possible existence of classes of individuals each with shared risk factors, and maybe a better method of incorporating the phenotypic heterogeneity underlying AF.

Methods and findings

Two prospective community-based cohort studies from Netherlands and United States were used. Prevention of Renal and Vascular End-stage Disease (PREVEND) study, started in 1997, and the Framingham Heart Study (FHS) Offspring cohort started in 1971, both with 10-years follow-up. The main objective was to determine the risk of AF using a latent class analysis, and compare the discrimination and reclassification performance with traditional regression analysis. Mean age in PREVEND was 49±13 years, 49.8% were men. During follow-up, 250(3%) individuals developed AF. We built a latent class model based on 18 risk factors. A model with 7 distinct classes (ranging from 341 to 1517 individuals) gave the optimum tradeoff between a high statistical model-likelihood and a low number of model parameters. All classes had a specific profile. The incidence of AF varied; class 1 0.0%, class 2 0.3%, class 3 7.5%, class 4 0.2%, class 5 1.3%, class 6 4.2%, class 7 21.7% (p<0.001). The discrimination (C-statistic 0.830 vs. 0.842, delta-C -0.013, p = 0.22) and reclassification (IDI -0.028, p<0.001, NRI -0.090, p = 0.049, and category-less-NRI -0.049, p = 0.495) performance of both models was comparable. The results were successfully replicated in a sample of the FHS study (n = 3162; mean age 58±9 years, 46.3% men).

Conclusions

Latent class analysis to build an AF risk model is feasible. Despite the heterogeneity in number and severity of risk factors between individuals at risk for AF, latent class analysis produces distinguishable groups.

Item Response Theory Analysis of ADHD Symptoms in Children With and Without ADHD

Item response theory (IRT) was separately applied to parent- and teacher-rated symptoms of attention-deficit/hyperactivity disorder (ADHD) from a pooled sample of 526 six- to twelve-year-old children with and without ADHD. The dimensional structure ADHD was first examined using confirmatory factor analyses, including the bifactor model. A general ADHD factor and two group factors, representing inattentive and hyperactive/impulsive dimensions, optimally fit the data. Using the graded response model, we estimated discrimination and location parameters and information functions for all 18 symptoms of ADHD. Parent- and teacher-rated symptoms demonstrated adequate discrimination and location values, although these estimates varied substantially. For parent ratings, the test information curve peaked between -2 and +2 SD, suggesting that ADHD symptoms exhibited excellent overall reliability at measuring children in the low to moderate range of the general ADHD factor, but not in the extreme ranges. Similar results emerged for teacher ratings, in which the peak range of measurement precision was from -1.40 to 1.90 SD Several symptoms were comparatively more informative than others; for example, is often easily distracted ("Distracted") was the most informative parent- and teacher-rated symptom across the latent trait continuum. Clinical implications for the assessment of ADHD as well as relevant considerations for future revisions to diagnostic criteria are discussed.

Incontinence in children with treated attention-deficit/hyperactivity disorder

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) and incontinence (nocturnal enuresis, daytime urinary incontinence and fecal incontinence) are common disorders in childhood. Both disorders are strongly associated with each other.

OBJECTIVE

ADHD can affect compliance to incontinence therapy in a negative way; it can also affect outcome. The aim of the present study was to assess the prevalence of incontinence, age of bladder and bowel control, and psychological symptoms in children having treatment for ADHD compared to a control group.

STUDY DESIGN

Forty children having treatment for ADHD (75% boys, mean age 11.4 years) and 43 matched controls (60.5% boys, mean age 10.7 years) were assessed. Their parents filled out questionnaires to assess: child psychopathology (Child Behavior Checklist), incontinence (Parental Questionnaire: Enuresis/Urinary Incontinence; Encopresis Questionnaire - Screening Version) and symptoms of the lower urinary tract (International-Consultation-on-Incontinence-Questionnaire - Pediatric Lower Urinary Tract Symptoms). The ICD-10 diagnoses and children's IQ were measured by standardized instruments (Kinder-DIPS, Coloured Progressive Matrices/Standard Progressive Matrices).

RESULTS

Rates of incontinence in the ADHD group (5% nocturnal enuresis, 5% daytime urinary incontinence, 2.5% fecal incontinence) did not differ significantly from incontinence rates in the control group (4.7% daytime urinary incontinence). More children in the ADHD group had Child Behavior Checklist scores in the clinical range. Further ICD-10 disorders were present in eight children with ADHD and in one control child. More children with ADHD had delayed daytime and nighttime bladder control, as well as delayed bowel control, than the controls.

DISCUSSION

The present study showed that if children are treated for their ADHD, according to standard practice guidelines, incontinence rates are similar to those without ADHD. More children with ADHD reached continence at a later age than the controls, which could be an indicator of maturational deficits in the central nervous system. Additionally, children with ADHD showed higher rates of clinically relevant psychological symptoms.

CONCLUSION

This study provides further information of the association between ADHD and incontinence. Treatment of ADHD may be associated with positive effects on incontinence outcomes. Therefore, children with ADHD should always be screened for incontinence problems and children with incontinence problems should also be screened for ADHD if symptoms of hyperactivity, inattention and/or impulsivity are also present.

State, trait anxiety and selective attention differences in Attention Deficit Hyperactivity Disorder (ADHD) subtypes

One of the disorders that most affects school performance is Attention Deficit Hyperactivity Disorder (ADHD). The criteria established by DSM distinguish three subtypes: inattentive, hyperactive-impulsive and combined. However, the expression of this disorder can be altered by its association with other disorders such as anxiety. The main goals of this study were to determine whether different patterns of attention (selective and concentration) and anxiety (state and trait anxiety) emerge from ADHD subtypes, and analyze how anxiety predicts the performance of students with ADHD in a selective attention task. The sample was made up of 220 children (6-12 years) divided into four groups: control group (n = 56), inattentive subtype (n = 54), hyperactive-impulsive subtype (n = 53), and combined subtype (n = 57). The results indicated that the groups differed significantly in the attention variables, and in state and trait anxiety. Multiple group comparisons revealed that the combined subtype exhibited higher trait anxiety, whereas the inattentive subtype showed more state anxiety. Additionally, trait anxiety predicted the students’ performance in the concentration variable of the attention task. These results suggest a novel path of significant interest concerning objective and reliable diagnostic assessment of ADHD.

Prediction of ADHD to anxiety disorders: an 11-year national insurance data analysis in Taiwan

OBJECTIVE

To prospectively investigate prediction of ADHD to anxiety disorders (ANXs) in a national sample of Taiwan.

METHOD

From the Taiwan National Health Insurance Dataset (1997-2007), we collected 2,385 cases of new diagnoses of ADHD from 1999 to 2003 and 9,540 sex-, age- and index dates of the first diagnosis of ADHD-matched cohort controls without ADHD. The outcome is age of the first diagnosis of ANXs until December 31, 2007.

RESULTS

More cases of ADHD (17.7%) developed ANXs than did matched controls (1.9%) with a younger age onset (12.7 years vs. 17.9 years) and a shorter "survival time" (1.4 years vs. 5.0 years). Cox models revealed a significant prediction of ADHD to ANXs controlling for other psychiatric comorbidities [Hazard ratio (HR) = 15.83]. The magnitude of such association was greater in males and decreased with older age of first ADHD diagnosis.

CONCLUSION

The findings imply that early detection and treatment for ADHD may offset later development of ANXs.

Comorbid externalising behaviour in AD/HD: evidence for a distinct pathological entity in adolescence

While the profiling of subtypes of Attention Deficit Hyperactivity Disorder (AD/HD) have been the subject of considerable scrutiny, both psychometrically and psychophysiologically, little attention has been paid to the effect of diagnoses comorbid with AD/HD on such profiles. This is despite the greater than 80% prevalence of comorbidity under the DSM-IV-TR diagnostic definitions. Here we investigate the event related potential (ERP) and psychometric profiles of Controls, AD/HD, and comorbid AD/HD (particularly AD/HD+ODD/CD) groups on six neurocognitive tasks thought to probe the constructs of selective and sustained attention, response inhibition and executive function. Data from 29 parameters extracted from a child group (age range 6 to 12; 52 Controls and 64 AD/HD) and from an adolescent group (age range 13 to 17; 79 Controls and 88 AD/HD) were reduced via a Principal Components Analysis, the 6 significant eigenvectors then used as determinants of cluster membership via a Two-Step Cluster Analysis. Two clusters were found in the analysis of the adolescent age group - a cluster dominated by Control and AD/HD participants without comorbidity, while the second cluster was dominated by AD/HD participants with externalising comorbidity (largely oppositional defiant/conduct disorder ODD/CD). A similar segregation within the child age group was not found. Further analysis of these objectively determined clusters in terms of their clinical diagnoses indicates a significant effect of ODD/CD comorbidity on a concurrent AD/HD diagnosis. We conclude that comorbid externalising behaviour in AD/HD constitutes a distinct pathological entity in adolescence.

Interaction of dopamine transporter (DAT1) genotype and maltreatment for ADHD: a latent class analysis

BACKGROUND

Although the association of the dopamine transporter (DAT1) gene and attention-deficit/hyperactivity disorder (ADHD) has been widely studied, far less is known about its potential interaction with environmental risk factors. Given that maltreatment is a replicated risk factor for ADHD, we explored the interaction between DAT1 and maltreatment with ADHD symptoms defined dimensionally and using latent class analysis (LCA).

METHOD

We tested the association of the 40 base-pair variable number of tandem repeats polymorphism in DAT1, maltreatment, and their interaction in 2,488 boys and girls from the National Longitudinal Study of Adolescent Health.

RESULTS

In boys, ADHD symptoms were optimally defined by four classes (Combined, Hyperactive/Impulsive, Inattentive, and Normal), whereas in girls, ADHD symptoms were defined by three classes (Combined, Combined-Mild, Normal). A significant DAT1 × maltreatment interaction revealed that maltreated girls homozygous for the 10-repeat allele had more symptoms of ADHD, and were also 2.5 times more likely to be classified in the Combined ADHD group than in the Normal Group.

CONCLUSIONS

The underlying structure of ADHD symptoms differed between boys and girls and DAT1 interacted with maltreatment to predict ADHD symptoms and ADHD status derived from LCA. Interactive exchanges between maltreatment and DAT1 for ADHD symptoms, and their implications for intervention, are discussed.

The latent classes of subclinical ADHD symptoms: convergences of multiple informant reports

The purpose of the present study was to conduct latent class analysis on the Hyperactivity scale of the Strengths and Difficulties Questionnaire in order to identify distinct subgroups of subclinical ADHD in a multi-informant framework. We hypothesized a similar structure between teachers and parents, and differences in symptom severity across latent classes. Data was collected from a non-referred sample of children aged 8-13 years. We performed latent class analyses on parent (n = 383) and teacher (n = 391) ratings of the Hyperactivity scale items from both versions of the questionnaire. Those children who had ratings from both informants (n = 272) were included in the cross-informant analyses, in which the similar or equivalent classes across raters were determined. A three-class solution for parent report and a five-class solution for teacher report emerged in the subsample of boys. For girls, a three-class structure for parents and a four-class structure for teachers were optimal. Besides non-symptomatic groups, mild and severe combined classes, mild inattentive-impulsive classes, and among boys, a mild hyperactive-impulsive class was obtained. The cross-informant analyses demonstrated that quite similar subgroups were detached regardless of informant; however, the teacher classes were somewhat more elaborated. The results are in line with the previous latent class analytic studies, and support the combination of dimensional and categorical approaches. The importance of milder symptoms and sub-threshold ADHD categories are emphasized for the fields of neuropsychology, neuroscience, and education, as well as for diagnosis and personalized treatment.

A common genetic network underlies substance use disorders and disruptive or externalizing disorders

Here we summarize evidence obtained by our group during the last two decades, and contrasted it with a review of related data from the available literature to show that behavioral syndromes involving attention deficit/hyperactivity disorder (ADHD), externalizing disorders, and substance-use disorder (SUD) share similar signs and symptoms (i.e., have a biological basis as common syndromes), physiopathological and psychopathological mechanisms, and genetic factors. Furthermore, we will show that the same genetic variants harbored in different genes are associated with different syndromes and that non-linear interactions between genetic variants (epistasis) best explain phenotype severity, long-term outcome, and response to treatment. These data have been depicted in our studies by extended pedigrees, where ADHD, externalizing symptoms, and SUD segregate and co-segregate. Finally, we applied here a new formal network analysis using the set of significantly replicated genes that have been shown to be either associated and/or linked to ADHD, disruptive behaviors, and SUD in order to detect significantly enriched gene categories for protein and genetic interactions, pathways, co-expression, co-localization, and protein domain similarity. We found that networks related to pathways involved in axon guidance, regulation of synaptic transmission, and regulation of transmission of nerve impulse are overrepresented. In summary, we provide compiled evidence of complex networks of genotypes underlying a wide phenotype that involves SUD and externalizing disorders.

Psychiatric problems associated with subthreshold ADHD and disruptive behaviour diagnoses in teenagers

AIM

To study the coexistence of subthreshold diagnoses of both attention deficit hyperactivity disorder (ADHD) and disruptive behaviour disorders (DBD) with other symptoms of child and adolescent psychiatric disorders as well as risk behaviours associated with smoking, alcohol and drug use.

METHODS

A population-based sample of twins including 177 girls and 135 boys was interviewed using the Swedish version of Kiddie-SADS Present and Lifetime Version (K-SADS-PL). Subthreshold diagnoses were compiled based on the ADHD and DBD criteria, where each criterion was assessed as 'possible' or 'certain' according to K-SADS-PL. The odds ratios (OR) between the subthreshold diagnoses and each of the screening questions in K-SADS-PL were calculated.

RESULTS

Subthreshold diagnoses of ADHD and DBD coexisted with the screening questions concerning depression, mania, panic attack, phobias, anorexia nervosa, motor tics and posttraumatic stress disorder (PTSD) in girls. In boys, these subthreshold diagnoses coexisted with symptoms of depression and PTSD. For both boys and girls, smoking and high alcohol consumption contributed to a high OR with regard to ADHD and DBD.

CONCLUSION

Subthreshold diagnoses of ADHD and DBD were risk factors for several other psychiatric symptoms as well as smoking and high alcohol consumption. Thus, a broad clinical assessment is needed for adolescents with such preliminary diagnoses.

Does attention-deficit/hyperactivity disorder have a dimensional latent structure? A taxometric analysis

An understanding of the latent structure of attention-deficit/hyperactivity disorder (ADHD) is essential for developing causal models of this disorder. Although some researchers have presumed that ADHD is dimensional and others have assumed that it is taxonic, there has been relatively little research directly examining the latent structure of ADHD. The authors conducted a set of taxometric analyses using data from the NICHD Study of Early Child Care and Youth Development (ns between 667 and 1,078). The results revealed a dimensional latent structure across a variety of different analyses and sets of indicators for inattention, hyperactivity/impulsivity, and ADHD. Furthermore, analyses of correlations with associated features indicated that dimensional models demonstrated stronger validity coefficients with these criterion measures than dichotomous models. These findings jibe with recent research on the genetic basis of ADHD and with contemporary models of ADHD.

A two-locus genetic interaction between LPHN3 and 11q predicts ADHD severity and long-term outcome

The severity of attention-deficit/hyperactivity disorder (ADHD) symptoms is a major predictor of long-term ADHD outcome. To investigate if two-locus interactions might predict ADHD severity, we studied a sample of 1341 individuals from families clustering ADHD, using the Vanderbilt Assessment Scale for Parents. Latent class cluster analysis was used to construct symptom profiles and classify ADHD severity. Single nucleotide polymorphisms (SNPs) spanning ADHD-linked chromosomal regions on chromosomes 4, 5, 10, 11, 12 and 17 were genotyped. SNPs associated with ADHD severity were identified and potential two-locus genetic interactions were tested. We found that SNPs within the LPHN3 gene interact with SNPs spanning the 11q region that contains DRD2 and NCAM1 not only to increase the risk of developing ADHD but also to increase ADHD severity. All these genes are identified to have a major role in shaping both brain development and function. These findings demonstrate that genetic interactions may predict the severity of ADHD, which in turn may predict long-term ADHD outcome.

Overview of animal models of attention deficit hyperactivity disorder (ADHD)

Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous, highly heritable, behavioral disorder that affects ∼5% to 10% of children worldwide. Although animal models cannot truly reflect human psychiatric disorders, they can provide insight into the disorder that cannot be obtained from human studies because of the limitations of available techniques. Genetic models include the spontaneously hypertensive rat (SHR), the Naples High Excitability (NHE) rat, poor performers in the 5-choice serial reaction time (5-CSRT) task, the dopamine transporter (DAT) knock-out mouse, the SNAP-25 deficient mutant coloboma mouse, mice expressing a human mutant thyroid hormone receptor, a nicotinic receptor knock-out mouse, and a tachykinin-1 (NK1) receptor knock-out mouse. Chemically induced models of ADHD include prenatal or early postnatal exposure to ethanol, nicotine, polychlorinated biphenyls, or 6-hydroxydopamine (6-OHDA). Environmentally induced models have also been suggested; these include neonatal anoxia and rat pups reared in social isolation. The major insight provided by animal models was the consistency of findings regarding the involvement of dopaminergic, noradrenergic, and sometimes also serotonergic systems, as well as more fundamental defects in neurotransmission.