ADHD and genetic syndromes

Diagnosis and pharmacological management of attention deficit hyperactivity disorder in adults with and without intellectual disability: cohort study using electronic health records

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is increasingly diagnosed in adults. People with intellectual disability have higher rates of ADHD yet there is little evidence on the presentation and pharmacological treatment of ADHD in this population or how this differs from the general population.

METHODS

Retrospective cohort study using data from electronic health records. Adults with intellectual disability newly diagnosed with ADHD between 2007 and 2022 were matched to adults with ADHD without intellectual disability and their clinical features and treatments were compared.

RESULTS

A total of 159 adults with ADHD and intellectual disability and 648 adults with ADHD without intellectual disability formed the dataset. Adults with intellectual disability had higher rates of psychiatric co-morbidity and spent more time under mental health services than those without intellectual disability. They were more likely to have recorded agitation, aggression, hostility, and mood instability, and less likely to have poor concentration recorded in the 12 months prior to the diagnosis of ADHD. Following diagnosis, people with intellectual disability were significantly less likely to be prescribed any medication for ADHD than controls without intellectual disability (adjusted odds ratio 0.60, 95% confidence interval 0.38-0.91), and were less likely to be prescribed stimulants (27.7% v 46.0%, p < 0.001).

CONCLUSIONS

The presence of behaviors that challenge in adults with intellectual disability may indicate co-occurring ADHD. Further work to define the safety and efficacy of medication for ADHD in adults with intellectual disability is needed to understand differences in prescription rates and to avoid inequities in care outcomes.

Integrative multi-omics analysis of genomic, epigenomic, and metabolomics data leads to new insights for Attention-Deficit/Hyperactivity Disorder

The evolving field of multi-omics combines data and provides methods for simultaneous analysis across several omics levels. Here, we integrated genomics (transmitted and non-transmitted polygenic scores [PGSs]), epigenomics, and metabolomics data in a multi-omics framework to identify biomarkers for Attention-Deficit/Hyperactivity Disorder (ADHD) and investigated the connections among the three omics levels. We first trained single- and next multi-omics models to differentiate between cases and controls in 596 twins (cases = 14.8%) from the Netherlands Twin Register (NTR) demonstrating reasonable in-sample prediction through cross-validation. The multi-omics model selected 30 PGSs, 143 CpGs, and 90 metabolites. We confirmed previous associations of ADHD with glucocorticoid exposure and the transmembrane protein family TMEM, show that the DNA methylation of the MAD1L1 gene associated with ADHD has a relation with parental smoking behavior, and present novel findings including associations between indirect genetic effects and CpGs of the STAP2 gene. However, out-of-sample prediction in NTR participants (N = 258, cases = 14.3%) and in a clinical sample (N = 145, cases = 51%) did not perform well (range misclassification was [0.40, 0.57]). The results highlighted connections between omics levels, with the strongest connections between non-transmitted PGSs, CpGs, and amino acid levels and show that multi-omics designs considering interrelated omics levels can help unravel the complex biology underlying ADHD.

Risk of attention deficit hyperactivity disorder diagnosis following multiple exposures to general anesthesia in the paediatric population: A systematic review and meta-analysis

Objectives

The risk of attention deficit hyperactivity disorder (ADHD) following multiple exposures to anesthesia has been debated. Our objective was to systematically review the literature to examine the association between multiple exposures to general anesthesia before age 5 and subsequent diagnosis of ADHD.

Methods

A systematic search of EMBASE, PubMed, and SCOPUS was performed using key search terms in February 2022. We included studies that: were published after 1980, included only otherwise healthy children who experienced two or more exposures to general anesthetic before age 5, diagnosed ADHD by a medical professional before age 19 years after exposure to general anesthetic, were cross-sectional, case-control, or cohort study, and were published in English. The results (expressed as hazard ratios [HR] and associated 95% confidence intervals [CI]) were pooled using meta-analytic techniques. Studies which did not present their results as HR and 95% CI were analyzed separately. GRADE was used to determine the certainty of the findings. PRISMA guidelines were followed at each stage of the review.

Results

Eight studies (196,749 children) were included. Five reported HR and 95% CI and were subsequently pooled for meta-analysis. Multiple exposures to anesthesia were associated with diagnosis of ADHD before the 19th year of life (HR: 1.71; 95% CI: 1.59, 1.84). Two of the three studies not used in the meta-analysis also found an increased risk of ADHD diagnosis following multiple anesthetic exposures.

Conclusions

There was an association between multiple early exposures to general anesthesia and later diagnosis of ADHD.

Profiling Autism and Attention Deficit Hyperactivity Disorder Traits in Children with SYNGAP1-Related Intellectual Disability

SYNGAP1-related ID is a genetic condition characterised by global developmental delay and epilepsy. Individuals with SYNGAP1-related ID also commonly show differences in attention and social communication/interaction and frequently receive additional diagnoses of Autism Spectrum Disorder (ASD) or Attention Deficit Hyperactivity Disorder (ADHD). We thus set out to quantify ASD and ADHD symptoms in children with this syndrome. To assess ASD and ADHD, parents and caregivers of a child with SYNGAP1-related ID (N = 34) or a typically developing control (N = 21) completed the Social Responsiveness Scale-2, the Social Communication Questionnaire with a subset of these also completing the Conners-3. We found that those with SYNGAP1-related ID demonstrated higher levels of autistic traits on both the SRS and SCQ than typically developing controls. On the SRS, those with SYNGAP1-related ID scored highest for restricted repetitive behaviours, and were least impaired in social awareness. On the Conners-3, those with SYNGAP1-related ID also showed a high prevalence of ADHD traits, with scores demonstrating difficulties with peer relations but relatively low occurrence of symptoms for DSM-5 conduct disorder and DSM-5 oppositional defiant disorder. Hierarchical clustering analysis highlighted distinct SYNGAP1-related ID subgroups for both ASD and ADHD traits. These findings provide further characterisation of the SYNGAP1-related ID behavioural phenotype, guiding diagnosis, assessment and potential interventions.

Update on genetics of attention deficit/hyperactivity disorder: current status 2023

PURPOSE OF REVIEW

Attention deficit/hyperactivity disorder (ADHD) shows consistently high heritability in genetic research. In this review article, we give an overview of the analysis of common and rare variants and some insight into current genetic methodology and their link to clinical practice.

RECENT FINDINGS

The heritability of about 80% is also high in comparison to other psychiatric diseases. However, recent studies estimate the proportion of heritability based on single nucleotide variants at 22%. The hidden heritability is an ongoing question in ADHD genetics. Common variants derived from mega genome-wide association analyses (GWAS) and subsequent meta-analyses usually display small effect sizes and explain only a small fraction of phenotypic variance. Rare variants, on the contrary, not only display large effect sizes but also rather explain, due to their rareness, a small fraction on phenotypic variance. Applying polygenic risk score (PRS) analysis is an improved approach of combining effect sizes of many common variants with clinically relevant measures in ADHD.

SUMMARY

We provide a concise overview on how genetic analysis, with a focus on GWAS and PRS, can help explain different behavioural phenotypes in ADHD and how they can be used for diagnosis and therapy prediction. Increased sample sizes of GWAS, meta-analyses and use of PRS is increasingly informative and sets the course for a new era in genetics of ADHD.

Psychometric Properties of Attention Measures in Young Children with Neurofibromatosis Type 1: Preliminary Findings

Children with neurofibromatosis type 1 (NF1) often demonstrate difficulties with attention and executive functioning that can be evident starting at a young age. There has been little research about which measures of attention are most suitable for use with young children with NF1. This pilot study explored several computerized measures of attention, a digits forward task, and parent report measures of attention to compare their reliability, validity, and the degree to which they capture attention difficulty in this population. Participants with NF1 ages 4 to 6 years were seen for one (n=2) or two (n=18) time points. Statistical analyses for evaluating evidence for test-retest reliability, convergent and discriminant validity, practice effects, and identification of difficulties were conducted. Each measure demonstrated relative strengths and weaknesses, and there may not be a “one size fits all” measure for use with young children with NF1. However, the Behavior Rating Inventory of Executive Function Preschool/Second Edition, Conners Early Childhood Inattention/Hyperactivity Scale, and the Conners Kiddie Continuous Performance Test Second Edition generally had the highest reliability and most evidence of validity. More specific recommendations are provided for the appropriate measure to use in clinical and research batteries.

Genetics of Attention-Deficit Hyperactivity Disorder

Attention-Deficit Hyperactivity Disorder (ADHD) has long been recognized as being a highly heritable condition and our understanding of the genetic contributions to ADHD has grown over the past few decades. This chapter will discuss the studies that have examined its heritability and the efforts to identify specific genetic risk-variants at the molecular genetic level. We outline the various techniques that have been used to characterize genetic contributions to ADHD, describing what we have learnt so far, what there is still to learn and the methodologies that can be used to further our knowledge. In doing so we will discuss research into rare and common genetic variants, polygenic risk scores, and gene-environment interplay, while also describing what genetic studies have revealed about the biological processes involved in ADHD and what they have taught us about the overlap between ADHD and other psychiatric and somatic disorders. Finally, we will discuss the strengths and limitations of the current methodologies and clinical implications of genetic research to date.

Mental health problems in children with intellectual disability

Intellectual disability ranks in the top ten causes of disease burden globally and is the top cause in children younger than 5 years. 2-3% of children have an intellectual disability, and about 15% of children present with differences consistent with an intellectual disability (ie, global developmental delay and borderline intellectual functioning). In this Review, we discuss the prevalence of mental health problems, interventions to address these, and issues of access to treatment and services. Where possible, we take a global perspective, given most children with intellectual disability live in low-income and middle-income countries. Approximately 40% of children with intellectual disability present with a diagnosable mental disorder, a rate that is at least double that in children without intellectual disability. Most risk factors for poor mental health and barriers to accessing support are not unique to people with intellectual disability. With proportionate universalism as the guiding principle for reducing poor mental health at scale, we discuss four directions for addressing the mental health inequity in intellectual disability.

Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is the most prevalent neurobehavioral disorder in childhood. The major components of this disorder are developmentally inappropriate levels of inattention and hyperactivity/impulsivity, which result in functional impairment in 1 or more areas of academic, social, and emotional function. In addition to the propensity for children to have some compromise of academic and emotional function, children with ADHD also have a higher frequency of co-occurring learning, cognitive, language, motor, and mental health disorders. Similarly, children with developmental disorders have a higher risk of co-occurring ADHD. The diagnosis of ADHD can be ascertained by a review of the risks for the condition, consideration of masquerading conditions, a careful history and physical examination, and the recognition of co-occurring disorders. The signs and symptoms of co-occurring disorders and the management of ADHD differ across early childhood, middle childhood, and adolescence. Management is largely limited to behavioral and pharmacologic interventions, and it favors behavioral strategies in early childhood, pharmacologic and behavioral strategies in middle childhood, and pharmacologic interventions in adolescence. This article offers an approach to the evaluation, presentation, and management of ADHD with a focus on guiding primary care pediatricians.

The relationship between cognition and mathematics in children with attention-deficit/hyperactivity disorder: a systematic review

Cognitive processes play an imperative role in children's mathematics learning. Difficulties in cognitive functioning are a core feature of Attention Deficit Hyperactivity Disorder (ADHD) in children, who also tend to show lower levels of mathematics attainment than their typically developing peers. This review (registration number: CRD42020169708) sought to aggregate findings from studies assessing the relationship between cognition and mathematics in children with a clinical ADHD diagnosis aged 4-12 years. A total of 11,799 studies published between 1992 and August 2020 were screened for eligibility using various database (PsycINFO, PubMed, SCOPUS, EMBASE, ERIC, Web of Science, and additional sources), from which four studies met inclusion criteria. A narrative synthesis was conducted on the correlations between mathematics and cognitive domains, including an evaluation of the risk of bias within the studies. Across four studies meeting inclusion criteria, memory, inhibitory control, and processing speed were assessed. The results showed a positive association between cognition and mathematics performance in this population. The strength of associations across these studies varied as a function of the cognitive domain in question, means by which mathematics performance was assessed, as well as whether confounding factors such as age and IQ were controlled for. Collectively, this review demonstrates a lack of research in this area and points to various methodological considerations for identifying the association between cognition and mathematics performance in ADHD.

Selective Effects of Methylphenidate on Attention and Inhibition in 22q11.2 Deletion Syndrome: Results From a Clinical Trial

BACKGROUND

Attention deficit and/or hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder in children with 22q11.2 deletion syndrome (22q11DS) and frequently persists into adulthood. Although medication with stimulant has been demonstrated to be highly effective in idiopathic ADHD, evidence in 22q11DS is still scarce. Previous studies have shown safety and effectiveness of methylphenidate (MPH) on core symptoms of ADHD as well as improvement of associated cognitive deficits. However, only a limited number of cognitive domains have been explored.

METHODS

Twenty-three participants with 22q11DS and attention difficulties, aged 8-24 years, entered a clinical trial aiming to specify the effects of MPH on clinical symptoms, cognition, and daily-life behavior. The effects of treatment were compared with/without medication in a within-subject design. The trial included both participants naïve to the molecule and chronic users.

RESULTS

Benefit from the treatment was demonstrated through a decrease in core ADHD symptoms, specifically inattention symptoms, and improvement of cognitive measures of attention and inhibition. Conversely, no significant change was found for other executive functions (such as cognitive flexibility, working memory, initiation), learning, or memory. Moreover, no significant improvement on ecological measures of daily-life executive functioning was found, possibly because of the short treatment period. We replicated safety, and although very frequent, side effects were of mild intensity and comparable with previous findings.

CONCLUSIONS

This study extends the current knowledge on the effects of MPH in patients with 22q11DS. Treatment was found to be effective for core ADHD symptoms and cognitive measures of attention and inhibition.

Effects of clonidine on progressive ratio schedule performance in Fmr1 knockout mice

RATIONALE

Fragile X syndrome (FXS), the most prevalent genetic form of intellectual disability, is characterized by intellectual impairment, impaired sociability, aggression, self-injury, hyperactivity, and attention deficits. A consequence of the hyperactivity and attention deficits is that individuals with FXS are frequently diagnosed with attention deficit hyperactivity disorder (ADHD) and treated with medications approved for ADHD (e.g., the α₂-agonist clonidine). The pharmacotherapy of FXS is often accompanied with behavioral therapies that rely on positive reinforcement and other operant principles. Despite the commonplace mixture of drug and behavioral therapy, little attention has been paid to the observation that clonidine or other psychotropic drugs may alter operant processes.

OBJECTIVES

In the present progressive ratio study, we used a knockout mouse model to test the effects of the fragile X genotype, the α₂-agonist clonidine, and the fragile X genotype and clonidine together on operant processes in a positive reinforcement task.

RESULTS

We found that clonidine decreased the progressive ratio breakpoint, increased the length of post-reinforcement pauses, and slowed the run rate. None of these effects varied by genotype. The effect on breakpoint suggests that clonidine alters motivation, but analysis using mathematical principles of reinforcement (MPR) did not rule out motor parameters as a contributor.

CONCLUSIONS

Our findings show that clonidine alters operant behavior and serve as a caution for combining clonidine with behavioral therapies that rely on positive reinforcement. Further research using different murine behaviors (e.g., touchscreen tasks) or different animal models (e.g., knockout rats) is needed to explore the interaction between pharmaco- and behavioral therapy.

The contribution of Xp22.31 gene dosage to Turner and Klinefelter syndromes and sex-biased phenotypes

Turner syndrome (TS) is a rare developmental condition in females caused by complete, or partial, loss of the second sex chromosome; it is associated with a number of phenotypes including short stature, ovarian failure and infertility, as well as neurobehavioural and cognitive manifestations. In contrast, Klinefelter syndrome (KS) arises from an excess of X chromosome material in males (typical karyotype is 47,XXY); like TS, KS is associated with infertility and hormonal imbalance, and behavioural/neurocognitive differences from gonadal sex-matched counterparts. Lower dosage of genes that escape X-inactivation may partially explain TS phenotypes, whilst overdosage of these genes may contribute towards KS-related symptoms. Here, I discuss new findings from individuals with deletions or duplications limited to Xp22.31 (a region escaping X-inactivation), and consider the extent to which altered gene dosage within this small interval (and of the steroid sulfatase (STS) gene in particular) may influence the phenotypic profiles of TS and KS. The expression of X-escapees can be higher in female than male tissues; I conclude by considering how lower Xp22.31 gene dosage in males may increase their likelihood of exhibiting particular phenotypes relative to females. Understanding the genetic contribution to specific phenotypes in rare disorders such as TS and KS, and to more common sex-biased phenotypes, will be important for developing more effective, and more personalised, therapeutic approaches.

Systematic Review and Meta-analysis: Mental Health in Children With Neurogenetic Disorders Associated With Intellectual Disability

OBJECTIVE

The behavioral phenotype of neurogenetic disorders associated with intellectual disability often includes psychiatric comorbidity. The objectives of this systematic review and meta-analysis were to systematically review the prevalence of psychiatric disorders and symptoms in children and adolescents with these disorders and compare phenotypic signatures between syndromes.

METHOD

MEDLINE and PsycINFO databases were searched for articles from study inception to December 2018. Eligible articles were peer reviewed, were published in English, and reported prevalence data for psychiatric disorders and symptoms in children and adolescents aged 4 to 21 years using a formal psychiatric assessment or a standardized assessment of mental health symptoms. Pooled prevalence was determined using a random-effects meta-analysis in studies with sufficient data. Prevalence estimates were compared with general population data using a test of binomial proportions.

RESULTS

Of 2,301 studies identified for review, 39 articles were included in the final pool, which provided data on 4,039 children and adolescents. Ten syndromes were represented, and five were predominant: Down syndrome, 22q11.2 deletion syndrome, fragile X syndrome, Williams syndrome, and Prader-Willi syndrome. The Child Behavior Checklist was the most commonly used assessment tool for psychiatric symptoms. The pooled prevalence with total scores above the clinical threshold was lowest for Down syndrome (32% [95% confidence interval, 19%-44%]) and highest for Prader-Willi syndrome (74% [95% CI, 65%-82%]) with each syndrome associated with significantly higher prevalence than in the general population. Parallel trends were observed for the internalizing and externalizing domains and social subscale scores.

CONCLUSION

Differential vulnerability for psychiatric phenotype expression across the disorders was observed. Syndromes with higher levels of social ability or competence appear to offer relative protection against developing psychopathology. This preliminary finding merits further exploration.

Integrating Genomics into Psychiatric Practice: Ethical and Legal Challenges for Clinicians

Psychiatric genomics is a rapidly growing field that holds much promise for improving risk prediction, prevention, diagnosis, treatment selection, and understanding of the pathogenesis of patients' symptoms. The field of psychiatry (i.e., professional organizations, mental health clinicians, educational institutions), however, needs to address numerous challenges to promote the responsible translation of genomic technologies and knowledge into psychiatric practice. The goal of this article is to review how clinicians currently encounter and use genomics in the clinic, to summarize the existing literature on how clinicians feel about the use of genomics in psychiatry, and to analyze foreseeable ethical and legal challenges for the responsible integration of genomics into psychiatric care at the structural and clinic levels. Structural challenges are defined as aspects of the larger system of psychiatric practice that constitute potential barriers to the responsible integration of genomics for the purposes of psychiatric care and prevention. These structural challenges exist at a level where professional groups can intervene to set standards and regulate the practice of psychiatry and genomics. Clinic-level challenges are day-to-day issues clinicians face when managing genomic tests in the clinic. We discuss the need for action to mitigate these challenges and maximize the clinical and social utility of psychiatric genomics, including the following: expanding genomics training among mental health clinicians; establishing practice guidelines that consider potential clinical, psychological, and social implications of psychiatric genomics; promoting an integrated care model for managing genomics in psychiatry; emphasizing patient engagement and informed consent when managing genomic testing in psychiatric care.

Genetics of ADHD: What Should the Clinician Know?

PURPOSE OF REVIEW

Attention deficit hyperactivity disorder (ADHD) shows high heritability in formal genetic studies. In our review article, we provide an overview on common and rare genetic risk variants for ADHD and their link to clinical practice.

RECENT FINDINGS

The formal heritability of ADHD is about 80% and therefore higher than most other psychiatric diseases. However, recent studies estimate the proportion of heritability based on singlenucleotide variants (SNPs) at 22%. It is a matter of debate which genetic mechanisms explain this huge difference. While frequent variants in first mega-analyses of genome-wideassociation study data containing several thousand patients give the first genome-wide results, explaining only little variance, the methodologically more difficult analyses of rare variants are still in their infancy. Some rare genetic syndromes show higher prevalence for ADHD indicating a potential role for a small number of patients. In contrast, polygenic risk scores (PRS) could potentially be applied to every patient. We give an overview how PRS explain different behavioral phenotypes in ADHD and how they could be used for diagnosis and therapy prediction. Knowledge about a patient's genetic makeup is not yet mandatory for ADHD therapy or diagnosis. PRS however have been introduced successfully in other areas of clinical medicine, and their application in psychiatry will begin within the next years. In order to ensure competent advice for patients, knowledge of the current state of research is useful forpsychiatrists.

Attention-deficit/hyperactivity disorder: diagnostic criteria, epidemiology, risk factors and evaluation in youth

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder in childhood with persistence into adulthood. It has a multifactorial etiology. Its chronicity, if diagnosis is missed or delayed, will result in significant negative impact on the individual's overall functioning and development. With the revised diagnostic criteria released in 2013 by the American Psychiatric Association, established standards of clinical practice continue to be applicable and valuable in the diagnosis and management of ADHD. In older children and adolescents, it is important to differentiate what is developmentally appropriate from problematic as ADHD has high correlation with poor outcomes, comorbidities, and low quality of life.

Young Adult Outcomes for Children With 22q11 Deletion Syndrome and Comorbid ADHD

Background

22q11.2 deletion syndrome (22q11DS) is a common microdeletion syndrome associated with a variety of negative health, cognitive, emotional, and behavioral outcomes. 22q11DS is comorbid with many psychiatric disorders including attention-deficit/hyperactivity disorder (ADHD). The current study aimed to investigate the cognitive, behavioral, and functional outcomes that a childhood ADHD diagnosis predicts to in adulthood.

Methods

This longitudinal study followed 52 individuals with 22q11DS over 9 years. Childhood ADHD was operationalized both categorically (Diagnostic and statistical manual - 4th edition (DSM-IV) ADHD diagnoses) and dimensionally (inattentive and hyperactive-impulsive symptoms) and was tested as predictors of young adult outcomes.

Results

As young adults, children with 22q11DS + baseline ADHD had more parent-reported executive dysfunction and lower levels of clinician-rated overall functioning than those with 22q11DS yet without ADHD. Dimensional symptoms of ADHD in childhood did not predict young adult outcomes. No self-report differences emerged between those with and without baseline ADHD. The majority (82.4%) of individuals with 22q11DS + baseline ADHD were never treated with an ADHD medication.

Conclusions

A categorical diagnosis of ADHD in childhood predicted a greater variety of worse outcomes than dimensional levels of ADHD symptoms. Despite the significant impact of comorbid ADHD in 22q11DS, evidence-based treatment rates were low.

Clinical and Therapeutic Challenges when Psychiatric Disorders Occur in Neurological Diseases: A Narrative Review

Background:

Over the course of the 20th century, neurology and psychiatry diverged and became two separate disciplines. Subsequently, the continuous progress of neurosciences confused their boundaries. However, with ‘the splitting’ and ‘the lumping’ approaches, relevant difficulties remain in targeting clinical and therapeutic goals, when psychiatric signs and symptoms co-occur with neurological diseases.

Objective:

The study summarize current evidence on psychiatric signs and symptoms comorbid with neurological diseases, with the aim to provide information on diagnostic problems and available therapeutic options.

Methods:

Finding from searches of publications on ‘PsycInfo’, ‘Medline’, and ‘Science Direct’, from January 1993 to December 2018 (25 years) is summarized in a narrative manner on six main neurological areas: congenital neurological illnesses (n=16), dementias (n=15), basal ganglia diseases (n=30), epilepsy (n=22), strokes/focal brain injuries (n=29), and neurological neoplastic/paraneoplastic diseases (n=15).

Results:

Clinical phenotypes of psychiatric syndromes are frequently described in neurological studies. Little evidence is provided on the most adequate therapeutic approaches.

Conclusion:

Psychiatric syndromes in comorbidity with neurological diseases are heterogeneous and severe; evidence-based treatments are scarce. Despite a model supporting an equal approach between psychiatric and neurological syndromes, psychiatric syndromes in neurological diseases have been described, to a relevant degree, as less important, leading to a hierarchical primate of the neurological manifestations, and thus, in our opinion, limiting the systematic studies on psychopharmacological treatments in this area.

Genetics of attention deficit hyperactivity disorder

Decades of research show that genes play an vital role in the etiology of attention deficit hyperactivity disorder (ADHD) and its comorbidity with other disorders. Family, twin, and adoption studies show that ADHD runs in families. ADHD's high heritability of 74% motivated the search for ADHD susceptibility genes. Genetic linkage studies show that the effects of DNA risk variants on ADHD must, individually, be very small. Genome-wide association studies (GWAS) have implicated several genetic loci at the genome-wide level of statistical significance. These studies also show that about a third of ADHD's heritability is due to a polygenic component comprising many common variants each having small effects. From studies of copy number variants we have also learned that the rare insertions or deletions account for part of ADHD's heritability. These findings have implicated new biological pathways that may eventually have implications for treatment development.

Persistence of self-injury, aggression and property destruction in children and adults with tuberous sclerosis complex

BACKGROUND

Individuals with tuberous sclerosis complex (TSC) are at increased risk of developing self-injurious behaviour. The persistence of this deleterious behaviour over years is reported in aetiologically heterogeneous samples to be between 60% and 80% but is unknown for TSC.

METHOD

In this study, we determined the 3-year persistence of self-injury in a sample (n = 52) of children (with and without ID) and adults (with ID) with TSC and examined characteristics associated with persistence.

RESULTS

Findings for self-injury were contrasted to those for aggression and property destruction to examine the specificity of results to this behaviour. Self-injury was persistent in 84.6% of those with TSC who showed this behaviour, in contrast to 66.7% both for aggression and destruction. Persistent self-injury was associated with poor self-help skills, greater overactivity/impulsivity and more behavioural indicators of pain. These latter two characteristics were also associated with persistent aggression. No characteristics were associated with persistence of property destruction.

CONCLUSION

These findings suggest that self-injurious behaviours in individuals with TSC, together with aggressive and destructive behaviours, are highly persistent and would benefit from targeted intervention. Poor adaptive skills, overactivity/impulsivity and painful health conditions may differentiate those at most risk for persistent self-injury or aggression.

Le TDAH chez les enfants et les adolescents, partie 1 : l’étiologie, le diagnostic et la comorbidité

Le trouble de déficit de l’attention/hyperactivité (TDAH) est un trouble neurodéveloppemental chronique. La Société canadienne de pédiatrie a préparé trois documents de principes après avoir effectué des analyses bibliographiques systématiques. Leurs objectifs s’établissent comme suit : 1) Résumer les données probantes cliniques à jour sur le TDAH. 2) Établir une norme pour les soins du TDAH. 3) Aider les cliniciens canadiens à prendre des décisions éclairées et fondées sur des données probantes pour rehausser la qualité des soins aux enfants et aux adolescents qui présentent cette affection.

Les thèmes abordés dans la partie 1, qui est axée sur le diagnostic, incluent la prévalence, la génétique, la physiopathologie, le diagnostic différentiel, ainsi que les troubles psychiatriques et les troubles du développement comorbides. En plus des recherches dans les bases de données, les auteurs ont analysé les directives les plus récentes de l’American Academy of Pediatrics , de l’American Academy of Child and Adolescent Psychiatry , du National Institute for Health and Clinical Excellence , du Scottish Intercollegiate Guidelines Network et de l’Eunethydis European ADHD Guidelines Group . Puisque le TDAH est un trouble hétérogène, son évaluation médicale complète devrait toujours inclure une anamnèse fouillée, un examen physique et une évaluation approfondie du diagnostic différentiel et des comorbidités connexes. Les auteurs proposent des recommandations précises sur la récolte d’information, les tests à effectuer et les orientations vers divers services.

ADHD in children and youth: Part 1-Etiology, diagnosis, and comorbidity

Attention-deficit hyperactivity disorder (ADHD) is a chronic neurodevelopmental disorder. Three position statements have been developed by the Canadian Paediatric Society, following systematic literature reviews. Statement objectives are to: 1) Summarize the current clinical evidence regarding ADHD,2) Establish a standard for ADHD care, and3) Assist Canadian clinicians in making well-informed, evidence-based decisions to enhance care of children and youth with this condition. Specific topics reviewed in Part 1, which focuses on diagnosis, include: prevalence, genetics, pathophysiology, differential diagnosis and comorbid psychiatric disorders and developmental disorders. In addition to database searches, the most recent guidelines of the American Academy of Pediatrics, the American Academy of Child and Adolescent Psychiatry, the National Institute for Health and Clinical Excellence, the Scottish Intercollegiate Guidelines Network, and the Eunethydis European ADHD Guidelines Group, were reviewed. Because ADHD is a heterogeneous disorder, comprehensive medical assessment for ADHD should always include a complete history, a physical examination, and a thorough consideration of differential diagnosis and related comorbidities. Specific recommendations for information gathering, testing, and referral are offered.

Motor dysfunction as research domain across bipolar, obsessive-compulsive and neurodevelopmental disorders

Although genuine motor abnormalities (GMA) are frequently found in schizophrenia, they are also considered as an intrinsic feature of bipolar, obsessive-compulsive, and neurodevelopmental disorders with early onset such as autism, ADHD, and Tourette syndrome. Such transnosological observations strongly suggest a common neural pathophysiology. This systematic review highlights the evidence on GMA and their neuroanatomical substrates in bipolar, obsessive-compulsive, and neurodevelopmental disorders. The data lends support for a common pattern contributing to GMA expression in these diseases that seems to be related to cerebello-thalamo-cortical, fronto-parietal, and cortico-subcortical motor circuit dysfunction. The identified studies provide first evidence for a motor network dysfunction as a correlate of early neurodevelopmental deviance prior to clinical symptom expression. There are also first hints for a developmental risk factor model of these mental disorders. An in-depth analysis of motor networks and related patho-(physiological) mechanisms will not only help promoting Research Domain Criteria (RDoC) Motor System construct, but also facilitate the development of novel psychopharmacological models, as well as the identification of neurobiologically plausible target sites for non-invasive brain stimulation.

CATEGORICAL DIAGNOSIS OF EXTREME HYPERACTIVITY, IMPULSIVITY, AND INATTENTION IN VERY YOUNG CHILDREN

Severe hyperactivity and impulsivity are common reasons for referral to infant mental health services. Past versions of ZERO TO THREE's () diagnostic nosology, the Diagnostic Classification of Mental and Developmental Disorders in Infancy and Early Childhood (DC:0-3), did not address this clinical issue because it had been addressed in other nosologies. These general diagnostic nosologies describe attention deficit hyperactivity disorder (ADHD), but with little attention to developmentally specific aspects of the diagnosis in very young children. Categorical diagnosis related to hyperactivity and impulsivity in very young children warrants careful review of existing literature. Explicit attention must be paid to ensure that categorical diagnoses serve to describe syndromes that cause significant impairment to the family to allow children and families to access effective supports and ensure that behaviors typical of the developmental level are not described as pathologic. This article reviews proposed diagnostic criteria for ADHD and overactivity disorder of toddlerhood as well as the rationale for the criteria and evidence supporting validity and reliability of the diagnoses in very young children. Clinical implications also are presented.

Looping Genomes: Diagnostic Change and the Genetic Makeup of the Autism Population

This article builds on Hacking's framework of "dynamic nominalism" to show how knowledge about biological etiology can interact with the "kinds of people" delineated by diagnostic categories in ways that "loop" or modify both over time. The authors use historical materials to show how "geneticization" played a crucial role in binding together autism as a biosocial community and how evidence from genetics research later made an important contribution to the diagnostic expansion of autism. In the second part of the article, the authors draw on quantitative and qualitative analyses of autism rates over time in several rare conditions that are delineated strictly according to genomic mutations in order to demonstrate that these changes in diagnostic practice helped to both increase autism's prevalence and create its enormous genetic heterogeneity. Thus, a looping process that began with geneticization and involved the social effects of genetics research itself transformed the autism population and its genetic makeup.

Effects of clonidine and methylphenidate on motor activity in Fmr1 knockout mice

Fragile X syndrome (FXS), a disorder caused by a mutation in the FMR1 gene, is often associated with Attention Deficit Hyperactivity Disorder (ADHD). Common treatments for the hyperactivity often seen in ADHD involve the use of stimulants and α2-adrenergic agonists. The Fmr1 knockout (KO) mouse has been found to be a valid model for FXS both biologically and behaviorally. Of particular interest to our research, the Fmr1 KO mouse has been demonstrated to show increased locomotion in comparison to wild type (WT) littermates. In the present study, we assessed the effects of clonidine (0.05 mg/kg) and methylphenidate (5 mg/kg) on motor activity in Fmr1 KO mice and their WT littermates in the open field test. Results showed that methylphenidate increased motor activity in both genotypes. Clonidine decreased motor activity in both genotypes, but the effect was delayed in the Fmr1 KO mice.

Planning deficit in children with neurofibromatosis type 1: a neurocognitive trait independent from attention-deficit hyperactivity disorder (ADHD)?

Neurofibromatosis type 1 is associated with executive dysfunctions and comorbidity with attention-deficit hyperactivity disorder (ADHD) in 30% to 50% of children. This study was designed to clarify the neurocognitive phenotype observed in neurofibromatosis type 1 by testing the hypothesis that children with neurofibromatosis type 1 have specific planning deficits independently from intellectual level and ADHD comorbidity. Eighteen children with neurofibromatosis type 1 were pair-matched to 18 children with ADHD and 18 healthy controls. All groups were assessed on the presence of ADHD symptoms (Conners Scales) and planning deficits (Tower of London). Compared with control group, groups with neurofibromatosis type 1 and ADHD demonstrated significant impairment of planning and problem solving. The lack of correlation between Tower of London results and Conners subscale scores in neurofibromatosis type 1 group confirmed that the planning and problem-solving deficit is not directly related to inattention level. These findings suggested that the executive impairment probably represents a peculiar trait of neurofibromatosis type 1 neurocognitive phenotype.

The comorbidity of ADHD and autism spectrum disorder

ADHD and autism spectrum disorder are common psychiatric comorbidities to each another. In addition, there is behavioral, biological and neuropsychological overlap between the two disorders. There are also several important differences between autism spectrum disorder and ADHD. Treatment strategies for the comorbid condition will also be reviewed. Future areas of research and clinical need will be discussed.

The genetics of attention deficit/hyperactivity disorder in adults, a review

The adult form of attention deficit/hyperactivity disorder (aADHD) has a prevalence of up to 5% and is the most severe long-term outcome of this common neurodevelopmental disorder. Family studies in clinical samples suggest an increased familial liability for aADHD compared with childhood ADHD (cADHD), whereas twin studies based on self-rated symptoms in adult population samples show moderate heritability estimates of 30-40%. However, using multiple sources of information, the heritability of clinically diagnosed aADHD and cADHD is very similar. Results of candidate gene as well as genome-wide molecular genetic studies in aADHD samples implicate some of the same genes involved in ADHD in children, although in some cases different alleles and different genes may be responsible for adult versus childhood ADHD. Linkage studies have been successful in identifying loci for aADHD and led to the identification of LPHN3 and CDH13 as novel genes associated with ADHD across the lifespan. In addition, studies of rare genetic variants have identified probable causative mutations for aADHD. Use of endophenotypes based on neuropsychology and neuroimaging, as well as next-generation genome analysis and improved statistical and bioinformatic analysis methods hold the promise of identifying additional genetic variants involved in disease etiology. Large, international collaborations have paved the way for well-powered studies. Progress in identifying aADHD risk genes may provide us with tools for the prediction of disease progression in the clinic and better treatment, and ultimately may help to prevent persistence of ADHD into adulthood.

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.

Left ventricular noncompaction

Left ventricular noncompaction (LVNC) is a rare form of cardiomyopathy of emerging importance. We report a case of a 3-months-old boy who presented with congestive heart failure due to LVNC.

[Mental retardation and ADHD]

Hyperactivity syndromes and disorders (ADHD and HKD) include the symptoms of overactivity, inattention, and impulsivity, which occur in many other mental disorders as well, including mental retardation (MR). It is not surprising that symptoms of ADHD occur significantly higher in children with learning disabilities. Dekker and Koot (2003) found a prevalence of 14.8 % for ADHD in Dutch children attending special schools, and Emerson (2003) reported rates of 8.7 % for HKD in children with global learning disability, representing a 10-fold increased risk compared to the prevalence of hyperactivity (0.9 %) in the general population sample. Yet only very few studies have been published concerning ADHD in children with mental retardation. Several features distinguish the diagnoses of ADHD and MR. In contrast to the limited knowledge about the differences and similarities of ADHD and MR, many studies considered stimulant medication as a pharmacological management strategy for children suffering from ADHD, MR, or both. According to these studies, psychostimulants may improve the target symptoms of hyperactivity, impulsivity, disinhibition, and inattention, albeit with caveats: ADHD symptoms in patients with MR may be less responsive to medical treatment than in patients without MR. Moreover, people with MR may be more susceptible to side effects.

Attention-deficit/hyperactivity disorder in childhood is associated with cognitive test profiles in the geriatric population but not with mild cognitive impairment or Alzheimer's disease

The frequency of ADHD in the aging population and its relationship to late-life cognitive decline has not been studied previously. To address this gap in our understanding, the Wender-Utah ADHD Rating scale (WURS) was administered to 310 geriatric subjects with cognitive status ranging from normal cognition to mild cognitive impairment to overt dementia. The frequency of WURS-positive ADHD in this sample was 4.4%. WURS scores were not related to cognitive diagnoses, but did show nonlinear associations with tasks requiring sustained attention. The frequency of ADHD appears stable across generations and does not appear to be associated with MCI or dementia diagnoses. The association of attentional processing deficits and WURS scores in geriatric subjects could suggest that such traits remain stable throughout life. Caution should be considered when interpreting cognitive test profiles in the aging population that exhibit signs and symptoms of ADHD, as attentional deficits may not necessarily imply the existence of an underlying neurodegenerative disease state.

Conformational-dependent and independent RNA binding to the fragile x mental retardation protein

The interaction between the fragile X mental retardation protein (FMRP) and BC1 RNA has been the subject of controversy. We probed the parameters of RNA binding to FMRP in several ways. Nondenaturing agarose gel analysis showed that BC1 RNA transcripts produced by in vitro transcription contain a population of conformers, which can be modulated by preannealing. Accordingly, FMRP differentially binds to the annealed and unannealed conformer populations. Using partial RNase digestion, we demonstrate that annealed BC1 RNA contains a unique conformer that FMRP likely binds. We further demonstrate that this interaction is 100-fold weaker than that the binding of eEF-1A mRNA and FMRP, and that preannealing is not a general requirement for FMRP's interaction with RNA. In addition, binding does not require the N-terminal 204 amino acids of FMRP, methylated arginine residues and can be recapitulated by both fragile X paralogs. Altogether, our data continue to support a model in which BC1 RNA functions independently of FMRP.

The neurobiological basis of ADHD

Attention-Deficit/Hyperactivity Disorder is not a single pathophysiological entity and appears to have a complex etiology. There are multiple genetic and environmental risk factors with small individual effect that act in concert to create a spectrum of neurobiological liability. Structural imaging studies show that brains of children with Attention-Deficit/Hyperactivity Disorder are significantly smaller than unaffected controls. The prefrontal cortex, basal ganglia and cerebellum are differentially affected and evidence indicating reduced connectivity in white matter tracts in key brain areas is emerging. Genetic, pharmacological, imaging, and animal models highlight the important role of dopamine dysregulation in the neurobiology of Attention-Deficit/Hyperactivity Disorder. To date, stimulants are the most effective psychopharmacological treatments available for Attention-Deficit/Hyperactivity Disorder. Currently only immediate release methylphenidate and atomoxetine are approved for the treatment of ADHD in Italy. Drug treatment should always be part of a comprehensive plan that includes psychosocial, behavioural and educational advice and interventions.