Latent class and factor analysis of DSM-IV ADHD: a twin study of female adolescents

Latent class analysis of behavior across dog breeds reveal underlying temperament profiles

Latent class analysis (LCA) is a type of modeling analysis approach that has been used to identify unobserved groups or subgroups within multivariate categorical data. LCA has been used for a wide array of psychological evaluations in humans, including the identification of depression subtypes or PTSD comorbidity patterns. However, it has never been used for the assessment of animal behavior. Our objective here is to identify behavioral profile-types of dogs using LCA. The LCA was performed on a C-BARQ behavioral questionnaire dataset from 57,454 participants representing over 350 pure breeds and mixed breed dogs. Two, three, and four class LCA models were developed using C-BARQ trait scores and environmental covariates. In our study, LCA is shown as an effective and flexible tool to classify behavioral assessments. By evaluating the traits that carry the strongest relevance, it was possible to define the basis of these grouping differences. Groupings can be ranked and used as levels for simplified comparisons of complex constructs, such as temperament, that could be further exploited in downstream applications such as genomic association analyses. We propose this approach will facilitate dissection of physiological and environmental factors associated with psychopathology in dogs, humans, and mammals in general.

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.

Attention deficit hyperactivity symptoms predict problematic mobile phone use

Attention-deficit-hyperactivity disorder (ADHD) is the most commonly diagnosed childhood disorder characterised by inattention, hyperactivity/impulsivity, or both. Some of the key traits of ADHD have previously been linked to addictive and problematic behaviours. The aim of the present study was to examine the relationship between problematic mobile phone use, smartphone addiction risk and ADHD symptoms in an adult population. A sample of 273 healthy adult volunteers completed the Adult ADHD Self-Report Scale (ASRS), the Mobile Phone Problem Usage Scale (MPPUS), and the Smartphone Addiction Scale (SAS). A significant positive correlation was found between the ASRS and both scales. More specifically, inattention symptoms and age predicted smartphone addiction risk and problematic mobile phone use. Our results suggest that there is a positive relationship between ADHD traits and problematic mobile phone use. In particular, younger adults with higher level of inattention symptoms could be at higher risk of developing smartphone addiction. The implication of our findings for theoretical frameworks of problematic mobile phone use and clinical practice are discussed.

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.

Using Large Aggregated De-Identified Electronic Health Record Data to Determine the Prevalence of Common Chronic Diseases in Pediatric Patients Who Visited Primary Care Clinics

OBJECTIVE

We used de-identified clinical data from multiple health care systems using different electronic health records (EHRs) to 1) quantify the prevalence of common pediatric chronic diseases, 2) investigate patent characteristics associated with common pediatric chronic diseases, and 3) compare the results of our methodology to determine chronic disease prevalence with traditional approaches.

METHODS

We used a HIPAA-compliant and de-identified web application (Explorys; IBM Watson Health Explorys Inc.) to identify patients 17 years old or younger from multiple health care systems in the US who were seen in primary care clinics between 2016-2018 to determine the most common chronic conditions in this age group. The prevalence of chronic conditions was compared between different age groups, genders, races/ethnicities, and insurance; odds ratios and confidence intervals were calculated and reported.

RESULTS

The top 6 chronic conditions identified by prevalence were: obesity/overweight (36.7%), eczema (15.8%), asthma (12.7%), food allergies (4.7%), attention deficit-hyperactivity disorder (4.09%) and hypertension (4.07%). Chronic conditions were generally more prevalent among relatively older pediatric patients, males, and African-American and multiracial groups.

CONCLUSIONS

Approximately 40% of children and adolescents have at least one chronic disease. Obesity/overweight, eczema, and asthma are the most common chronic diseases of childhood, in the US, among those seeking care in health care systems with EHRs. The work compiled herein demonstrates that aggregated, standardized, normalized and de-identified population-level EHR data can provide both sufficient insight and statistical power to calculate the prevalence of chronic diseases and the odds ratio of various risk factors.

Overdiagnosis of Attention-Deficit/Hyperactivity Disorder in Children and Adolescents: A Systematic Scoping Review

Importance

Reported increases in attention-deficit/hyperactivity disorder (ADHD) diagnoses are accompanied by growing debate about the underlying factors. Although overdiagnosis is often suggested, no comprehensive evaluation of evidence for or against overdiagnosis has ever been undertaken and is urgently needed to enable evidence-based, patient-centered diagnosis and treatment of ADHD in contemporary health services.

Objective

To systematically identify, appraise, and synthesize the evidence on overdiagnosis of ADHD in children and adolescents using a published 5-question framework for detecting overdiagnosis in noncancer conditions.

Evidence Review

This systematic scoping review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Extension for Scoping Reviews and Joanna Briggs Methodology, including the PRISMA-ScR Checklist. MEDLINE, Embase, PsychINFO, and the Cochrane Library databases were searched for studies published in English between January 1, 1979, and August 21, 2020. Studies of children and adolescents (aged ≤18 years) with ADHD that focused on overdiagnosis plus studies that could be mapped to 1 or more framework question were included. Two researchers independently reviewed all abstracts and full-text articles, and all included studies were assessed for quality.

Findings

Of the 12 267 potentially relevant studies retrieved, 334 (2.7%) were included. Of the 334 studies, 61 (18.3%) were secondary and 273 (81.7%) were primary research articles. Substantial evidence of a reservoir of ADHD was found in 104 studies, providing a potential for diagnoses to increase (question 1). Evidence that actual ADHD diagnosis had increased was found in 45 studies (question 2). Twenty-five studies showed that these additional cases may be on the milder end of the ADHD spectrum (question 3), and 83 studies showed that pharmacological treatment of ADHD was increasing (question 4). A total of 151 studies reported on outcomes of diagnosis and pharmacological treatment (question 5). However, only 5 studies evaluated the critical issue of benefits and harms among the additional, milder cases. These studies supported a hypothesis of diminishing returns in which the harms may outweigh the benefits for youths with milder symptoms.

Conclusions and Relevance

This review found evidence of ADHD overdiagnosis and overtreatment in children and adolescents. Evidence gaps remain and future research is needed, in particular research on the long-term benefits and harms of diagnosing and treating ADHD in youths with milder symptoms; therefore, practitioners should be mindful of these knowledge gaps, especially when identifying these individuals and to ensure safe and equitable practice and policy.

Latent Class Analysis of ADHD Symptoms in Korean Children and Adolescents

Objective: The objective of this study was to conduct latent class analysis (LCA) of ADHD symptoms to characterize the underlying structure of ADHD. Method: Participants were recruited from September 2012 to January 2015 from the Department of Psychiatry of Asan Medical Center, Seoul, Korea. Diagnoses of ADHD and comorbid psychiatric disorders were confirmed with the Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL). We performed LCA of ADHD symptoms in those who had (n = 141, age = 8.1 ± 2.3 years, 106 boys) and did not have (n = 82, age = 9.1 ± 2.5 years, 40 boys) ADHD. Results: A three-class solution was found to be the best model, revealing classes of children with mostly combined and hyperactive/impulsive subtypes of ADHD (Class 1), non-ADHD (Class 2), and inattentive subtype of ADHD (Class 3). Conclusion: The three-class solution with LCA supports a two-factor two-class structure of ADHD symptoms.

Modeling Learning Patterns to Predict Placebo Analgesic Effects in Healthy and Chronic Orofacial Pain Participants

Successfully predicting the susceptibility of individuals to placebo analgesics will aid in developing more effective pain medication and therapies, as well as aiding potential future clinical use of placebos. In pursuit of this goal, we analyzed healthy and chronic pain patients' patterns of responsiveness during conditioning rounds and their links to conditioned placebo analgesia and the mediating effect of expectation on those responses. We recruited 579 participants (380 healthy, 199 with temporomandibular disorder [TMD]) to participate in a laboratory placebo experiment. Individual pain sensitivity dictated the temperatures used for high- and low-pain stimuli, paired with red or green screens, respectively, and participants were told there would be an analgesic intervention paired with the green screens. Over two conditioning sessions and one testing session, participants rated the painfulness of each stimulus on a visual analogue scale from 0 to 100. During the testing phase, the same temperature was used for both red and green screens to assess responses to the placebo effect, which was defined as the difference between the average of the high-pain-cue stimuli and low-pain-cue stimuli. Delta scores, defined as each low-pain rating subtracted from its corresponding high-pain rating, served as a means of modeling patterns of conditioning strength and placebo responsiveness. Latent class analysis (LCA) was then conducted to classify the participants based on the trajectories of the delta values during the conditioning rounds. Classes characterized by persistently greater or increasing delta scores during conditioning displayed greater placebo analgesia during testing than those with persistently lower or decreasing delta scores. Furthermore, the identified groups' expectation of pain relief acted as a mediator for individual placebo analgesic effects. This study is the first to use LCA to discern the relationship between patterns of learning and the resultant placebo analgesia in chronic pain patients. In clinical settings, this knowledge can be used to enhance clinical pain outcomes, as chronic pain patients with greater prior experiences of pain reduction may benefit more from placebo analgesia.

Epidemiology of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents in Africa: a systematic review and meta-analysis

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorders in childhood and adolescence, affecting 2.2 to 17.8% of all school-aged children and adolescents. ADHD in children has been associated with a wide range of developmental deficits including limitations of learning or control of executive functions as well as global impairments of social skills. However, no review has been conducted to report the consolidated magnitude of ADHD in children and adolescents in Africa. Therefore, this systematic review and meta-analysis aimed to estimate the prevalence of ADHD in Africa.

METHODS

Following the PRISMA guideline, we systematically reviewed and meta-analyzed studies that investigated the prevalence of ADHD in Africa from three electronic databases (PubMed, Embase, and Scopus). We also looked at the reference lists of included studies to include other relevant studies. Subgroup and sensitivity analysis was carried out based on the study setting, tools used to measure ADHD, sex of participants, and the subtype of ADHD. Heterogeneity across the studies was evaluated using Cochran's Q- and the I ²-test. We assessed potential publication bias using Egger's test and visual inspection of the symmetry in funnel plots.

RESULTS

In the present meta-analysis, 7452 articles were initially identified and evaluated. Of these, 12 studies that met the inclusion criteria were included in the final analysis. The pooled prevalence of ADHD in children and adolescents in Africa was 7.47% (95% CI 60-9.26). The prevalence of ADHD was apparently greater in boys (10.60%) than in girls (5.28%) with a male:female ratio of 2.01:1. In our subgroup analysis, the predominantly inattentive type (ADHD-I) was found to be the most common subtype of ADHD, followed by hyperactive-impulsive type (ADHD-HI) and the combined type (ADHD-C) with the prevalence of 2.95%, 2.77%, and 2.44% respectively. The predominantly inattentive type (ADHD-I) was the most common type of ADHD in both boys (4.05%) and girls (2.21%). The funnel plot and Egger's regression tests provided no evidence of substantial publication bias in the prevalence of ADHD.

CONCLUSION

Our systematic review suggested a higher prevalence of ADHD (7.47%) in children and adolescents in Africa, indicating that ADHD is a serious public health problem in children and adolescents in Africa. The prevalence of ADHD was considerably greater in males than in females. The predominantly inattentive type (ADHD-I) was the most common type of ADHD in both males and females. Greater attention needs to be paid to the prevention and treatment of ADHD.

Factor Analysis of the Persian Version of the Voice Disability Coping Questionnaire

INTRODUCTION

Voice disorders can affect the quality of life and coping mechanisms and also coping mechanisms can affect the way in which patients deal with their voice problems. People with voice disorders need to use coping strategies to deal with the problems caused by their voice disorder. The purpose of this study was to examine the psychometric properties and cultural adaptation of the Voice Disability Coping Questionnaire in the Iranian population.

METHODS

The translation and cross-cultural adaptation procedures were performed according to the basic rules and instructions set by the International Quality of Life Assessment Project. Two hundred and forty-eight adults (218 patients with voice disorder and 30 healthy controls) were participated in the study. Face and content validity, clinical validity, and construct validity of the questionnaire were investigated by modern psychometric methods.

RESULTS

Quantitative methods were used to measure content validity and all items were detected applicable. This means that the final version was clear and easy to answer. Clinical validity shows that the Persian version of VDCQ can distinguish between patients and healthy controls (P < 0.001). The construct validity of the VDCQ was tested in a cross-sectional study. The questionnaire was analyzed by exploratory and confirmatory factor analyses. Investigation of initial communality and after extraction of factors by Varimax rotation method showed that the share of items for all items in the questionnaire except item 12, is higher than 0.5. Therefore, item 12 should be removed from the questionnaire (Table 3). Based on the confirmatory factor analysis model, items 2 and 10, whose factor load were less than 0.4, were excluded from the questionnaire (Fig. 1). For reliability the Cronbach's alpha coefficient and ICC were obtained as 0.82 and 0.99, respectively. The results of studying the role of items in the reliability of the VDCQ showed that all items increase internal consistency.

CONCLUSION

Based on modern statistical analysis conducted in this study, the original 15 item questionnaire was reduced to 12 item. The 12 item questionnaire is a valid and reliable tool for quantifying coping strategies in people with voice disorder.

The Application of Latent Class Analysis for Investigating Population Child Mental Health: A Systematic Review

Background: Latent class analysis (LCA) can be used to identify subgroups of children with similar patterns of mental health symptoms and/or strengths. The method is becoming more commonly used in child mental health research, but there are reservations about the replicability, reliability, and validity of findings. Objective: A systematic literature review was conducted to investigate the extent to which LCA has been used to study population mental health in children, and whether replicable, reliable and valid findings have been demonstrated. Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. A search of literature, published between January 1998 and December 2017, was carried out using MEDLINE, EMBASE, PsycInfo, Scopus, ERIC, ASSIA, and Google Scholar. A total of 2,748 studies were initially identified, of which 23 were eligible for review. The review examined the methods which studies had used to choose the number of mental health classes, the classes that they found, and whether there was evidence for the validity and reliability of the classes. Results: Reviewed studies used LCA to investigate both disparate mental health symptoms, and those associated with specific disorders. The corpus of studies using similar indicators was small. Differences in the criteria used to select the final LCA model were found between studies. All studies found meaningful or useful subgroups, but there were differences in the extent to which the validity and reliability of classes were explicitly demonstrated. Conclusions : LCA is a useful tool for studying and classifying child mental health at the population level. Recommendations are made to improve the application and reporting of LCA and to increase confidence in findings in the future, including use of a range of indices and criteria when enumerating classes, clear reporting of methods for replicability, and making efforts to establish the validity and reliability of identified classes.

Problematic Video Game Play and ADHD Traits in an Adult Population

This study examined the relationship between problematic video game play (PVGP), video game usage, and attention deficit hyperactivity disorder (ADHD) traits in an adult population. A sample of 205 healthy adult volunteers completed the Adult ADHD Self-Report Scale (ASRS), a video game usage questionnaire, and the Problem Video Game Playing Test (PVGT). A significant positive correlation was found between the ASRS and the PVGT. More specifically, inattention symptoms and time spent playing video games were the best predictors of PVGP. No relationship was found between frequency and duration of play and ADHD traits. Hyperactivity symptoms were not associated with PVGP. Our results suggest that there is a positive relationship between ADHD traits and problematic video game play. In particular, adults with higher level of self-reported inattention symptoms could be at higher risk of PVGP.

Latent Impulsivity Subtypes in Substance Use Disorders and Interactions with Internalizing and Externalizing Co-Occurring Disorders

This study explored the clinical importance of latent impulsivity subtypes within a sample of individuals with substance use disorders (SUDs) and high rates of co-occurring disorders (CODs) receiving residential treatment, aiming to assess the heterogeneity of the associations between SUDs and CODs across such impulsivity subtypes. The abbreviated Barratt impulsiveness scale was used to assess motor and cognitive (attentional and nonplanning) impulsivity, a structured interview for diagnosis of SUD and CODs, and other clinimetric measures for severity of substance use. Latent class analysis was conducted to extract subgroups of impulsivity subtypes and Poisson regression to analyze effects of interactions of classes by CODs on severity of substance use. 568 participants were evaluated. Results featured a four-class model as the best-fitted solution: overall high impulsivity (OHI); overall low impulsivity; high cognitive-low motor impulsivity; and moderate cognitive-low motor impulsivity (MC-LMI). OHI and MC-LMI concentrated on most of the individuals with CODs, and individuals within OHI and MC-LMI showed more severity of substance use. The expression of this severity relative to the impulsivity subtypes was modified by their interaction with internalizing and externalizing CODs in very heterogeneous ways. Our findings suggest that knowing either the presence of trait-based subtypes or CODs in individuals with SUDs is not enough to characterize clinical outcomes, and that the analysis of interactions between psychiatric categories and behavioral traits is necessary to better understand the expressions of psychiatric disorders.

Screening for ADHD in a Sample of Egyptian Adolescent School Students

OBJECTIVE

To screen for ADHD in a sample of Egyptian adolescent students, and study the distribution of different subtypes of ADHD, associated comorbidities, and sociodemographic correlates.

METHOD

A total of 925 adolescents were randomly selected and screened by the Conners-Wells' Adolescent Self-Report Scale-Short form (CASS:S), and potential cases were further assessed by the Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime versions (K-SADS-PL).

RESULTS

A total of 87 students (9.4%) had potential ADHD diagnosis with evident preponderance in boys (13.8%, n = 58) than in girls (5.8%, n = 29) with a ratio of 2:1 ( p = .000, χ² = 17.328). The hyperactive-impulsive subtype comprised the majority of cases (54.7%, n = 41). Psychiatric comorbidity was invariably present (85.1%, n = 74). Nearly half the cases had poor academic achievement (43.7%, n = 34). Positive correlates included family history of psychiatric disorders, the order of birth, and parental disharmony.

CONCLUSION

ADHD is prevalent in Egyptian adolescents and is associated with high psychiatric comorbidity and a pronounced effect on academic performance.

Behavioral Adjustment in the U. S. Elementary School: Cross-Validation of a Person-Oriented Typology of Risk

Cluster analysis is a popular technique in the social sciences for classifying subjects into smaller, homogenous groups; however, cluster solutions are not often externally replicated. This study externally replicated the seven-cluster solution found by the BASC TRS-C Norm sample. External replication was conducted on two independent samples of children between the ages of 6 and I1. Replication was shown by three methods: (a) independent cluster analysis, (b) cross-classification among grouping procedures, and (c) relationships between disciplinary actions and cluster membership. Results showed that the seven-cluster behavioral typology of child behavior could be replicated. Implications for future use of the behavioral typology are discussed.

The Factor Structure of DSM-IV Attention Deficit-Hyperactivity Symptoms: A Confirmatory Factor Analysis of the ADHD-SRS

Since the inception of DSM-IV considerable research has focused on the conceptualization of attention deficit-hyperactivity disorder (ADHD) as a multidimensional construct. This study utilized confirmatory factor analysis (CFA) to examine the adequacy of fit for the two-factor model (hyperactivity/impulsivity and inattention) previously specified for the ADHD Symptoms Rating Scale (ADHD-SRS), Parent Version. The invariance of this model across gender was then examined using a second, independent sample of children. The results indicate that a two-factor model provides the best fit for the data using the ADHD-SRS. Additionally, findings suggested that this model is invariant across gender. These results provide support both for the psychometric properties of the ADHD-SRS and the subtypes of ADHD specified in the DSM-IV

Maternal Ratings of the ADHD Symptoms: Subtypes Versus Severity in Clinic-Referred Children and Adolescents

OBJECTIVE

This study used confirmatory factor analysis (CFA), latent class analysis (LCA), and factor mixture model (FMM) to ascertain the best model for ADHD symptoms, as presented in the Strengths and Weaknesses of ADHD-Symptoms and Normal Behavior Scale (SWAN).

METHOD

Mother ratings of the ADHD symptoms of 418 clinic-referred children and adolescents were obtained.

RESULTS

The findings provided most support for an FMM with two classes (less severe inattention [IA] and hyperactivity/impulsivity [HI] symptoms and more severe IA/HI symptoms) and two factors (IA and HI) model. The more severe class had more individuals with the ADHD diagnosis, especially the combined type.

CONCLUSION

The findings are discussed in relation to dimensional and categorical views of ADHD.

The Structure of Co-Occurring Bullying Experiences and Associations with Suicidal Behaviors in Korean Adolescents

Objective

This study had two main goals: to examine the structure of co-occurring peer bullying experiences among adolescents in South Korea from the perspective of victims and to determine the effects of bullying on suicidal behavior, including suicidal ideation and suicide attempts, among adolescents.

Method

This study used data gathered from 4,410 treatment-seeking adolescents at their initial visits to 31 local mental health centers in Gyeonggi Province, South Korea. The structure of peer bullying was examined using latent class analysis (LCA) to classify participants’ relevant experiences. Then, a binomial logistic regression adjusted by propensity scores was conducted to identify relationships between experiences of being bullied and suicidal behaviors.

Results

The LCA of experiences with bullying revealed two distinct classes of bullying: physical and non-physical. Adolescents who experienced physical bullying were 3.05 times more likely to attempt suicide than those who were not bullied. Victims of (non-physical) cyber bullying were 2.94 times more likely to attempt suicide than were those who were not bullied.

Conclusions

Both physical and non-physical bullying were associated with suicide attempts, with similar effect sizes. Schools and mental health professionals should be more attentive than they currently are to non-physical bullying.

Common prefrontal cortical gene expression profiles between adolescent SHR/NCrl and WKY/NCrl rats which showed inattention behavior

Factor analyses of attention-deficit/hyperactivity (ADHD) symptoms divide the behavioral symptoms of ADHD into two separate domains, one reflecting inattention and the other, a combination of hyperactivity and impulsivity. Identifying domain-specific genetic risk variants may aid in the discovery of specific biological risk factors for ADHD. In contrast with data available on genes involved in hyperactivity and impulsivity, there is limited information on the genetic influences of inattention. Transcriptional profiling analysis in animal models of disorders may provide an important tool to identify genetic involvement in behavioral phenotypes. To explore some of the potential genetic underpinnings of ADHD inattention, we examined common differentially expressed genes (DEGs) in the prefrontal cortex of SHR/NCrl, the most validated animal model of ADHD and WKY/NCrl, animal model of ADHD-inattentive type. In contrast with Wistar rats, strain representing the "normal" heterogeneous population, SHR/NCrl and WKY/NCrl showed inattention behavior in the Y-maze task. The common DEGs in the PFC of SHR/NCrl and WKY/NCrl vs. Wistar rats are those involved in transcription (e.g. Creg1, Thrsp, Zeb2), synaptic transmission (e.g. Atp2b2, Syt12, Chrna5), neurological system process (e.g. Atg7, Cacnb4, Grin3a), and immune response (e.g. Atg7, Ip6k2, Mx2). qRT-PCR analyses validated expression patterns of genes representing the major functional gene families among the DEGs (Grin3a, Thrsp, Vof-16 and Zeb2). Although further studies are warranted, the present findings indicate novel genes associated with known functional pathways of relevance to ADHD which are assumed to play important roles in the etiology of ADHD-inattentive subtype.

Sex differences in ADHD symptom severity

BACKGROUND

Males show higher rates of attention deficit hyperactivity disorder (ADHD) than do females. Potential explanations include genuine etiological differences or artifact.

METHODS

2,332 twin and sibling youth participated in behavioral and cognitive testing. Partially competing models of symptom severity distribution differences, the mean difference, and variance difference models, were tested within a randomly selected subsample. The Delta method was used to test for mediation of sex differences in ADHD symptom severity by processing speed, inhibition and working memory.

RESULTS

The combined mean difference and variance difference models fully explained the sex difference in ADHD symptom severity. Cognitive endophenotypes mediated 14% of the sex difference effect.

CONCLUSIONS

The sex difference in ADHD symptom severity is valid and may be due to differing genetic and cognitive liabilities between the sexes.

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.

The four causes of ADHD: a framework

In addition to the symptoms singled out by the diagnostic criteria for Attention-Deficit Hyperactivity Disorder (ADHD), a comprehensive definition should inform us of the events that trigger ADHD in both its acute and chronic manifestations; the neurobiology that underlies it; and the evolutionary forces that have kept it in the germ line of our species. These factors are organized in terms of Aristotle's four kinds of "causes," or explanations: formal, efficient, material, and final. This framework systematizes the nosology, biology, psychology, and evolutionary pressures that cause ADHD.

[Psychiatric comorbidity related to children with attention deficit hyperactivity disorder at schools in Sfax, Tunisia]

INTRODUCTION

Attention deficit hyperactivity disorder (ADHD) is a prevalent behavioral disorder particularly noticed among school children. It is often associated with other psychological troubles at the origin of an additional difficulty that has to be overcome.

OBJECTIVE

Our research's aim was to study the comorbidity of school-aged children diagnosed with ADHD in Sfax, Tunisia.

SUBJECTS AND METHODS

A cross-sectional descriptive study was carried out from 1st April 2008 to 1st October 2008. Five hundred and thirteen pupils aged between 6 and 12, from primary arbitrarily chosen schools from Sfax were subjected to this study. Measurements were carried out in two steps: parents and teachers of each child filled in separately Conners questionnaire, then children with a score in subscales inattention, hyperactivity impulsivity higher than 70 were selected for psychiatric interview that was intended to confirm or to invalidate the ADHD diagnosis and the possible comorbid diagnosis. The diagnoses were made according to DSM-IV-TR.

RESULTS

We have noticed that 109 pupils exhibited at least one pathological score on the Conners questionnaire. After interviewing these 109 pupils, the results have shown that 51 among them fulfilled criteria of ADHD. Prevalence of ADHD was found to be 9.94 %. About 72.54 % of children with ADHD had one or more comorbid disorder: learning disabilities (23.52 % of cases), anxiety disorder (31.37 % of cases), oppositional defiant disorder in (15.68 % of cases), mood disorder (3.92 % of cases), enuresis (13.72 % of cases) and slight mental retardation (1.95 % of cases).

CONCLUSION

We can say that this study has shown that ADHD school children's psychiatric comorbidity is similar to any other previous study.

Mechanisms underpinning inattention and hyperactivity: neurocognitive support for ADHD dimensionality

BACKGROUND

Taxometric and behavioral genetic studies suggest that attention deficit hyperactivity disorder (ADHD) is best modeled as a dimension rather than a category. We extended these analyses by testing for the existence of putative ADHD-related deficits in basic information processing (BIP) and inhibitory-based executive function (IB-EF) in individuals in the subclinical and full clinical ranges. Consistent with the dimensional model, we predicted that ADHD-related deficits would be expressed across the full spectrum, with the degree of deficit linearly related to the severity of the clinical presentation.

METHOD

A total of 1547 children (aged 6-12 years) participated in the study. The Development and Well-Being Assessment (DAWBA) was used to classify children into groups according to levels of inattention and hyperactivity independently: (1) asymptomatic, (2) subthreshold minimal, (3) subthreshold moderate and (4) clinical ADHD. Neurocognitive performance was evaluated using a two-choice reaction time task (2C-RT) and a conflict control task (CCT). BIP and IB-EF measures were derived using a diffusion model (DM) for decomposition of reaction time (RT) and error data.

RESULTS

Deficient BIP was found in subjects with minimal, moderate and full ADHD defined in terms of inattention (in both tasks) and hyperactivity/impulsivity dimensions (in the 2C-RT). The size of the deficit increased in a linear manner across increasingly severe presentations of ADHD. IB-EF was unrelated to ADHD.

CONCLUSIONS

Deficits in BIP operate at subclinical and clinical levels of ADHD. The linear nature of this relationship provides support for a dimensional model of ADHD in which diagnostic thresholds are defined in terms of clinical and societal burden rather than representing discrete pathophysiological states.

Attention-deficit/hyperactivity disorder polygenic risk scores predict attention problems in a population-based sample of children

OBJECTIVE

Clinically, attention-deficit/hyperactivity disorder (ADHD) is characterized by hyperactivity, impulsivity, and inattention and is among the most common childhood disorders. These same traits that define ADHD are variable in the general population, and the clinical diagnosis may represent the extreme end of a continuous distribution of inattentive and hyperactive behaviors. This hypothesis can be tested by assessing the predictive value of polygenic risk scores derived from a discovery sample of ADHD patients in a target sample from the general population with continuous scores of inattention and hyperactivity. In addition, the genetic overlap between ADHD and continuous ADHD scores can be tested across rater and age.

METHOD

The Psychiatric Genomics Consortium has performed the largest genome-wide analysis (GWA) study of ADHD so far, including 5,621 clinical patients and 13,589 controls. The effects sizes of single nucleotide polymorphisms (SNPs) estimated in this meta-analysis were used to obtain individual polygenic risk scores in an independent population-based cohort of 2,437 children from the Netherlands Twin Register. The variance explained in Attention Problems (AP) scale scores by the polygenic risk scores was estimated by linear mixed modeling.

RESULTS

The ADHD polygenic risk scores significantly predicted both parent and teacher ratings of AP in preschool- and school-aged children.

CONCLUSION

These results indicate genetic overlap between a diagnosis of ADHD and AP scale scores across raters and age groups and provides evidence for a dimensional model of ADHD. Future GWA studies on ADHD can likely benefit from the inclusion of population-based cohorts and the analysis of continuous scores.

I can't get no satisfaction: potential causes of boredom

A variety of causes of boredom have been proposed including environmental, motivational, emotional, and cognitive factors. Here, we explore four potential cognitive causes of boredom: inattention, hyperactivity, impulsivity, and executive dysfunction. Specifically, we examine the unique and common associations between these factors and boredom propensity. Recent research has established that the two most commonly used measures of boredom propensity (BPS and BSS) are not measuring the same underlying construct. Thus, a second goal of the present project is to determine the unique and common roles of inattention, hyperactivity, impulsivity and poor executive system functioning in predicting the BPS and BSS specifically. The findings reveal that inattention, hyperactivity and executive dysfunction predict boredom propensity, with shared variance accounting for the greater part of this effect. Further, executive dysfunction and hyperactivity uniquely predict boredom propensity as measured by the BPS and BSS, respectively.

Adolescent and caregiver reports of ADHD symptoms among inner-city youth: agreement, perceived need for treatment, and behavioral correlates

OBJECTIVE

This study investigated adolescent and caregiver reports of ADHD symptoms in a sample of clinically referred inner-city adolescents.

METHOD

Participants (N = 168) included youth ages 12-18 (54% male, 98% ethnic minority) and their caregivers who each completed diagnostic interviews of ADHD symptoms and assessments of perceived need for ADHD treatment and correlated behavior problems.

RESULTS

Informants showed poor agreement on DSM-IV diagnostic categories and also dimensional scales, Inattention/Disorganization (I/D) and Hyperactivity/Impulsivity (H/I). Both caregiver and adolescent reports of I/D symptoms, but not H/I symptoms, were related to perceived need for ADHD treatment. Caregiver reports were linked to behavioral correlates typically associated with ADHD: I/D symptoms correlated with planning/organization and socioemotional deficits, and H/I symptoms correlated with externalizing and behavior regulation deficits. In contrast, adolescent reports of I/D were related to internalizing and externalizing problems, and their reports of H/I correlated with externalizing only. Few gender effects were found.

CONCLUSION

Study results underscore the developmental salience of I/D symptoms and have implications for ADHD diagnosis and treatment planning for adolescents.

Innovations and recent trends in the treatment of ADHD

Initiatives to develop better-tolerated, more efficacious pharmacological agents with improved drug delivery systems have driven recent research in attention-deficit hyperactivity disorder (ADHD). While stimulants are the primary pharmacotherapy for ADHD, these drugs have a limited duration of action and a subset of patients will either fail to respond to these medications or have side effects that preclude their use. The development of atomoxetine, the first nonstimulant approved for ADHD, has been followed by additional innovative research, such as the methylphenidate transdermal system, modafinil, NRP-104 and cholinergic agents. This review highlights some of the recent trends in ADHD treatment and the current status of promising treatment options that may help to shape the future of ADHD treatment.

Cross-informant agreement on child and adolescent withdrawn behavior: a latent class approach

Withdrawn behavior (WB) relates to many developmental outcomes, including pervasive developmental disorders, anxiety, depression, psychosis, personality disorders and suicide. No study has compared the latent profiles of different informants' reports on WB. This study uses multi-informant latent class analyses (LCA) of the child behavior checklist (CBCL), teacher report form (TRF) and youth self-report (YSR) to examine phenotypic variance in WB. LCA was applied to the CBCL, TRF and YSR of 2,031 youth (ages 6-18); of which 276 children were clinically-referred. A 4-class solution for the CBCL and 3-class solutions for the YSR and TRF were optimal. The CBCL yielded low symptoms, predominantly shy or secretive moderate symptoms, and all symptoms classes. The TRF lacked the moderate--secretive class, and the YSR lacked the moderate--shy class. Agreement was low. LCA shows similar structure of withdrawn behavior across informants but characterizations of moderate WB vary.

Exploration of ADHD Subtype Definitions and Co-Occurring Psychopathology in a Missouri Population-Based Large Sibship Sample

BACKGROUND

There is some debate regarding the utility of Attention-Deficit/ Hyperactivity Disorder (ADHD) subtypes as currently defined. Differences in co-occurring psychopathology among subtypes would support the validity of subtype definitions.

OBJECTIVE

To explore how ADHD subtype relates to co-occurring psychopathology in a large population-based sample of children and adolescents (n=5744).

METHOD

Parents completed the Strengths and Weaknesses of ADHD-symptoms and Normal behavior (SWAN) questionnaire, the Child Behavior Checklist (CBCL) and the Social Responsiveness Scale (SRS). Methods including discriminant analysis, principal components analysis, and fractional polynomial regression were used to examine the relationship between ADHD diagnostic subtypes and co-occurring psychopathology.

RESULTS

Children with different ADHD subtypes show differences on several CBCL subscales. A combination of CBCL subscales and SRS score had good ability to discriminate ADHD subtypes. Conversely, for the same overall number of ADHD symptoms, individuals who present with both inattentive and hyperactive/impulsive symptoms exhibit higher severity of co-occurring psychopathology on a summary measure derived from principal components analysis of the CBCL subscales and SRS. This includes some subjects who fail to meet the DSM-IV-TR ADHD symptom criterion due to having less than 6 inattentive and less than six hyperactive-impulsive symptoms, yet have ADHD symptom severity similar to those with the inattentive or hyperactive-impulsive subtype.

CONCLUSIONS

Several convergent lines of analysis provide support for the continued use of ADHD subtypes (or current presentation symptom profiles), as evidenced by differences in co-existing psychopathlogy. We also found that current diagnostic criteria may fail to identify a potentially impaired group of individuals who have low-to-moderate levels of both inattention and hyperactivity/impulsivity. Under the upcoming DSM-5, it will be important for clinicians to consider the option of giving an ADHD "not elsewhere classified" diagnosis to such children.

Inattention symptoms predict level of depression in early childhood

OBJECTIVE

To investigate the potential bidirectional relationships between severity of inattention and depression across early childhood.

METHODS

Children (N = 216) from the New York, NY, metropolitan area were recruited when they were aged 3 to 4 years (T1) and studied again at age 6 (T2) and 7 (T3) years. Child inattention symptoms were measured using the Kiddie-Schedule for Affective Disorders and Schizophrenia for School-Aged Children-Present and Lifetime, along with both parent and teacher reports on the Behavior Assessment System for Children, Second Edition (BASC-2). Severity of child depression was assessed at each time point using parent and teacher reports on the BASC-2. After examining correlations between child inattention and depression, structural equation modeling was used to investigate whether child inattention was longitudinally related to child depression, and whether child depression symptoms were associated with later child inattention.

RESULTS

Severity of child inattention at T1 and T2 was longitudinally associated with increased severity of child depression at T2 and T3, respectively. Early child depression was not longitudinally associated with later child inattention.

CONCLUSION

Child inattention is a risk factor for increased levels of child depression. Pediatricians and clinicians who assess children's inattention symptoms also need to investigate symptoms of depression. This study makes a case for treating children's inattention symptoms at preschool and early childhood, before emotional problems become more severe.

Phenotype refinement for comorbid attention deficit hyperactivity disorder and reading disability

Comorbidity between Attention Deficit Hyperactivity Disorder (ADHD) and reading disability (RD) is common; however, the heritability of this comorbidity is not well understood. This may be due to the complexity and heterogeneity of ADHD and RD phenotypes. Using alternative ADHD-RD sub-phenotypes instead of those arising from the DSM-IV may lead to greater success in the search for comorbid ADHD-RD susceptibility genes. Therefore, this study aims to refine ADHD-RD phenotypes into homogenous informative sub-phenotypes using latent class analysis (LCA). LCA was performed on 2,610 Australian twin families (6,535 individuals) in order to generate probabilistic genetically distinct classes that define ADHD-RD subtypes, including comorbidity, based on related symptom clusters. The LCA separated the phenotypes for ADHD and RD into nine classes. One class was unaffected; three classes demonstrated the three DSM-IV subtypes of ADHD, three subtypes showed different severities of RD, and two classes expressed a combination of RD and ADHD subtypes. LCA proved effective in refining the phenotypes of ADHD alone, RD alone, and ADHD-RD comorbidity, and its ability to classify them into homogenous groups based on clusters of symptoms, suggesting that the latent classes may be robust enough to use in molecular genetic studies.

Attention-deficit/hyperactivity disorder in older adults: prevalence and possible connections to mild cognitive impairment

Attentional deficits are frequently seen in isolation as the presenting sign and symptom of neurodegenerative disease, manifest as mild cognitive impairment (MCI). Persistent ADHD in the geriatric population could well be misconstrued as MCI, leading to the incorrect assumption that such persons are succumbing to a neurodegenerative disease process. Alternatively, the molecular, neuroanatomic, or neurochemical abnormalities seen in ADHD may contribute to the development of de novo late life neurodegenerative disease. The present review examines the issue of causality vs confound regarding the association of ADHD with MCI, suggesting that both are tenable hypotheses.

Separate and overlapping relationships of inattention and hyperactivity/impulsivity in children and adolescents with attention-deficit/hyperactivity disorder

There is debate regarding the dimensional versus categorical nature of attention-deficit/hyperactivity disorder (ADHD). This study utilized confirmatory factor analysis to examine this issue. ADHD symptoms rated on interviews and rating scales from a large sample of individuals (ages 3-17, 74 % male, 75 % Caucasian) with ADHD were examined (n = 242). Four potential factor structures were tested to replicate prior findings in a sample with a wide age range and included only participants who met DSM-IV-TR diagnostic criteria for ADHD. Correlations with executive function measures were performed to further assess the separability and validity of the derived factors. The data support a bifactor model with a general ADHD factor and two specific factors, inattention and hyperactivity/impulsivity. Importantly, the individual factors were also differentially correlated with executive functioning measures. This study adds to a growing literature suggesting both a general component to ADHD, as well as dimensional traits of inattention and hyperactivity/impulsivity, associated with distinct executive functioning profiles. The presence of a general underlying factor contraindicates separating the inattentive and combined subtypes of ADHD into distinct disorders.

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.

The latent structure of attention deficit/hyperactivity disorder in an adult sample

The vast majority of studies that have examined the latent structure of attention deficit/hyperactivity disorder (ADHD) in children and adolescents have concluded that ADHD has a dimensional latent structure. In other words, ADHD symptomatology exists along a continuum and there is no natural boundary or qualitative distinction (i.e., taxon) separating youth with ADHD from those with subclinical inattention or hyperactivity/impulsivity problems. Although adult ADHD appears to be less prevalent than ADHD in youth (which could suggest a more severe adult ADHD taxon), researchers have yet to examine the latent structure of ADHD in adults. The present study used a sample (N = 600) of adults who completed a self-report measure of ADHD symptoms. The taxometric analyses revealed a dimensional latent structure for inattention, hyperactivity/impulsivity, and ADHD. These findings are consistent with previous taxometric studies that examined ADHD in children and adolescents, and with contemporary polygenic and multifactorial models of ADHD.

Annual research review: categories versus dimensions in the classification and conceptualisation of child and adolescent mental disorders--implications of recent empirical study

The question of whether child and adolescent mental disorders are best classified using dimensional or categorical approaches is a contentious one that has equally profound implications for clinical practice and scientific enquiry. Here, we explore this issue in the context of the forth coming publication of the DSM-5 and ICD-11 approaches to classification and diagnosis and in the light of recent empirical studies. First, we provide an overview of current category-based systems and dimensional alternatives. Second, we distinguish the various strands of meaning and levels of analysis implied when we talk about categories and dimensions of mental disorder--distinguishing practical clinical necessity, formal diagnostic systems, meta-theoretical beliefs and empirical reality. Third, we introduce the different statistical techniques developed to identify disorder dimensions and categories in childhood populations and to test between categorical and dimensional models. Fourth, we summarise the empirical evidence from recent taxometric studies in favour of the 'taxonomic hypothesis' that mental disorder categories reflect discrete entities with putative specific causes. Finally, we explore the implications of these findings for clinical practice and science.

Association of positive and negative parenting behavior with childhood ADHD: interactions with offspring monoamine oxidase A (MAO-A) genotype

Relatively little is known about the potential interplay between genetic and environmental influences on attention-deficit/hyperactivity disorder (ADHD), including gene-environment interaction (G×E). There is evidence that parenting behavior interacts with offspring genotype in the development of externalizing problems, but studies have largely focused on explicit maltreatment rather than differentiated measures of parenting behavior, including positive and negative parenting. We tested the interactive effects of the 30-base pair variable number tandem repeat (VNTR) polymorphism of the monoamine oxidase A gene (MAO-A) with positive and negative parenting behavior on parent- and teacher ratings of inattention and hyperactivity symptoms among 150 6-9 year-old boys with and without ADHD. Negative parenting predicted parent and teacher ratings of inattention symptoms, but only among boys with high-activity MAO-A genotype. MAO-A genotype did not moderate the association of positive parenting and parent- and teacher ratings of ADHD. We discuss the potential role of interactive exchanges between parenting behavior and child genotype in the development and persistence of ADHD and related behavior problems.

Understanding the phenotypic structure of adult retrospective ADHD symptoms during childhood in the United States

Attention-deficit/hyperactivity disorder (ADHD) is a highly heterogeneous disorder, and the phenotypic structure comprising inattentive and hyperactive-impulsive type symptoms has been the focus of a growing body of recent research. Methodological studies are needed to better characterize phenotypes to advance research as well as clinical practice. A large U.S. population-based sample of young adults (N = 14,307, aged 17-28 years, 52.8% female) retrospectively reported their experiences of childhood ADHD symptoms. Factor analysis, latent class analysis, and factor mixture modeling of ADHD symptoms were compared to determine which underlying structure best fit the data. Fit statistics as well as substantive criteria compared models within and across model subtypes. Analyses supported a two-factor two-class structure for both male and female subjects. The two latent factors represented inattentive and hyperactive-impulsive symptom dimensions. The two latent classes divided people into a smaller affected class and a larger unaffected class. Individuals who reported having been diagnosed with ADHD were more likely to be in the affected class (OR male subjects = 4.03, 95% CI [2.65, 6.13]; OR female subjects = 5.65, 95% CI [3.15, 10.10]). This work aids in the understanding of ADHD symptomatology within the population; a majority of people experience very low symptom severity, whereas a minority of people experience high symptom severity. Within this high symptom group, however, variability in symptom experiences exists. Empirical models can be helpful in clarifying ADHD phenotypic structure that has the potential to advance research on the etiology and consequences of ADHD symptoms.

Ascertainment of a Mid-Western US Female Adolescent Twin Cohort for Alcohol Studies: Assessment of Sample Representativeness Using Birth Record Data

Female twin pairs were identified from birth records, and their families invited to participate in a prospective study of the determinants of alcohol problems in women. We investigated sampling biases arising because of failure to locate families, or non-cooperation of families. Out of 2644 families with a live-born pair (born between July 1975 and December 1986) who survived beyond infancy, contact was established and a brief screening interview completed with 90% (N = 2380). Fewer than 6% of located families declined to participate in the initial screening interview. Predictors of failure to locate a family or to obtain a screening interview were identified from information recorded in birth records, and from neighborhood characteristics identified from 1990 US Census block group data for the family residence when the twins were born. African-American families were under-represented in the final sample, but this effect was barely significant when other variables were controlled for. Under-represented were families where the mother was 19 or younger at the birth of the twins, where the mother herself was born out-of-state, or where information about biological father was not reported in the birth record. Non-participating families on average came from neighborhoods with a higher proportion of residents living in poverty, and with a higher proportion of African-American residents. Sampling biases were however small. The unusual cooperativeness in research of families with twins persists.

The Latent Class Structure of ADHD Is Stable Across Informants

Previous studies have looked at the structure of attention-deficit/hyperactivity disorder (ADHD) using latent class analysis (LCA) of Child Behavior Checklist (CBCL) or Diagnostic and Statistical Manual of Mental Disorders (DSM) symptom structure. These studies have identified distinct classes of children with inattentive, hyperactive, or combined subtypes and have used these classes to refine genetic analyses. The objective of the current report is to determine if the latent class structure of ADHD subtypes is consistent across informant using the Conners' Rating Scales (CRS). LCA was applied to CRS forms from mother, father, and teacher reports of 1837, 1329 and 1048 latency aged Dutch twins, respectively. The optimal solution for boys was a 5-class solution for mothers, a 3-class solution for fathers, and a 4-class solution for teachers. For girls, a 4-class solution for mothers and a 3-class for fathers and teachers was optimal. Children placed into a class by one informant had markedly increased odds ratio of being placed into the same or similar class by the other informants. Results from LCA using Dutch twins with the CRS show stability across informants suggesting that more stable phenotypes may be accessible for genotyping using a multi-informant approach.

Estimation of Prevalence of DSM-IV and Latent Class-Defined ADHD Subtypes in a Population-Based Sample of Child and Adolescent Twins

The goal of this study is to determine the prevalence and age of onset of Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSMIV; American Psychiatric Association, 1994) and latent class-derived attention deficit/hyperactivity disorder (ADHD) subtypes in a population-based twin sample of boys and girls. Missouri birth records identified families with a twin pair 7 to 18 years of age. Telephone screening interviews for ADHD symptoms were completed for 5007 families. Diagnostic assessments were administered to 564 families with at least one twin meeting screening criteria, plus 183 control families. Prevalence and age of onset for both ADHD nosologies were calculated by sex and zygosity from parent report data. The prevalence of any DSM-IV ADHD was 6.2% overall, 7.4% in boys and 3.9% in girls. The inattentive subtype was most common in boys; the combined subtype was most common in girls. The mean age of onset of symptoms in children with any DSM-IV ADHD was 3.5 years, with no significant differences between boys and girls. Prevalences of latent class defined ADHD subtypes also varied by sex with the severe inattentive and combined classes more common in boys than girls. The age of onset of symptoms did not differ between boys and girls but were higher than in the DSM-IV subtypes. Findings in this twin sample showed that clinically significant ADHD, defined by either DSM-IV or latent class criterion, has an early age of onset and is more common in boys than girls. As clinical samples are most commonly composed of male combined subtypes, the inattentive subtype of both sexes in the general population is an under- treated segment of the general population.