Neurobiologie des Aufmerksamkeitsdefizit-/Hyperaktivitätssyndroms

An updated review on animal models to study attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a neuropsychiatric disorder affecting both children and adolescents. Individuals with ADHD experience heterogeneous problems, such as difficulty in attention, behavioral hyperactivity, and impulsivity. Recent studies have shown that complex genetic factors play a role in attention-deficit hyperactivity disorders. Animal models with clear hereditary traits are crucial for studying the molecular, biological, and brain circuit mechanisms underlying ADHD. Owing to their well-managed genetic origins and the relative simplicity with which the function of neuronal circuits is clearly established, models of mice can help learn the mechanisms involved in ADHD. Therefore, in this review, we highlighting the important genetic animal models that can be used to study ADHD.

[Attachment Representations, Critical Life Events and ADHD in Boys at 6 to 10 Years of Age]

Attachment Representations, Critical Life Events and ADHD in Boys at 6 to 10 Years of Age The importance of the attachment theory was repeatedly pointed out in the literature for understanding children with attention deficit hyperactivity disorder (ADHD) with regard to their emotional state. Symptoms of ADHD, like attention deficits, motor agitation and impulsivity are seen as risk factors for insecure attachment in the parent-child relationship. The acquisition of attachment representations in children with ADHD might help to describe - and individual classify - the syndromes of this behavioural disorder better. The aims of the present study are, therefore, the investigation of attachment representations and critical life events in boys with ADHD. We focused on boys only, since they are particularly prone to develop ADHD. Using the story-completion technique, we investigated whether boys with ADHD showed insecure attachment more frequently compared to boys without ADHD. 31 boys with ADHD at six to ten years of age were recruited in two different clinics. Of these, 29 % showed a secure and 71 % showed an insecure attachment representation. Within insecure attachment, the ambivalent attachment representation occurred most frequently (41 %). On average, we found 2.3 critical life events. The enhanced frequency of the ambivalent attachment representation indicates that ADHD might be linked to externalizing behaviour. The results support the hypothesis that ADHD is increasingly associated with insecure attachment. The binding theory is able to contribute to a better understanding of the emotional state in boys with ADHD.

Methylphenidate for Attention-Deficit and Hyperactivity Disorder in Adult Patients With Substance Use Disorders: Good Clinical Practice

Attention-deficit and hyperactivity disorder (ADHD) is a widespread neurodevelopmental disorder in children and adolescents, persisting into adulthood in a majority of them. ADHD and substance use disorders (SUDs) commonly co-occur in the clinical adult population. The higher-than-normal prevalence rates of SUDs in people with ADHD indicate increased risk for developing SUD. This narrative review deals with the question of whether or not adults with both disorders should be treated with methylphenidate (MPH), addressing specific issues surrounding this form of treatment. MPH is considered as first-line pharmacotherapy for ADHD. However, because of its stimulant-like reinforcing properties, MPH has a significant addictive potential to which persons with SUDs are especially susceptible. Appropriate treatment is therefore complex. Because of concerns about misuse and diversion of MPH medication, clinicians may be reluctant to use MPH to manage ADHD symptoms in these patients. However, it is essential to diagnose and treat ADHD adequately as appropriate therapy reduces the impairments, as well as the risk of developing comorbid disorders and poor treatment response. MPH should not be deprived of these patients because of the risk for misuse, especially as several strategies can be applied to minimize this risk. To conclude, carefully applied guideline-based diagnostics to clarify the potential presence of ADHD as well as a responsible prescription practice in a well-defined therapeutic setting with reliable monitoring of medication intake and regular consultations are essential conditions for a safe and proficient MPH treatment of ADHD in patients with SUD.

Expression of the ADHD candidate gene Diras2 in the brain

The distinct subgroup of the Ras family member 2 (DIRAS2) gene has been found to be associated with attention-deficit/hyperactivity disorder (ADHD) in one of our previous studies. This gene is coding for a small Ras GTPase with unknown function. DIRAS2 is highly expressed in the brain. However, the exact neural expression pattern of this gene was unknown so far. Therefore, we investigated the expressional profile of DIRAS2 in the human and murine brain. In the present study, qPCR analyses in the human and in the developing mouse brain, immunocytological double staining on murine hippocampal primary cells and RNA in situ hybridization (ISH) on brain sections of C57BL/6J wild-type mice, have been used to reveal the expression pattern of DIRAS2 in the brain. We could show that DIRAS2 expression in the human brain is the highest in the hippocampus and the cerebral cortex, which is in line with the ISH results in the mouse brain. During mouse brain development, Diras2 levels strongly increase from prenatal to late postnatal stages. Co-expression studies indicate Diras2 expression in glutamatergic and catecholaminergic neurons. Our findings support the idea of DIRAS2 as a candidate gene for ADHD as the timeline of its expression as well as the brain regions and cell types that show Diras2 expression correspond to those assumed to underlie the pathomechanisms of the disease.

ADHS und Mediensucht bei Kindern und Jugendlichen

Zusammenfassung. Zielsetzung: Es wird der aktuelle Forschungsstand über den Zusammenhang von ADHS und Mediensucht dargestellt, die beide zu den häufigsten kinder- und jugendpsychiatrischen Störungen gehören. Methodik: Anhand einer systematischen Literaturrecherche wurden aus 190 relevanten Suchergebnissen zum Thema ADHS und Mediensucht bei Kindern und Jugendlichen 125 Artikel zum Download ausgewählt. 57 Veröffentlichungen konnten eingeschlossen werden. Ergebnisse: Es besteht eine klare Evidenz, dass ADHS mit einer hohen Rate an Mediensucht verbunden ist und andererseits bei Mediensucht eine hohe Rate an ADHS-Symptomen gefunden wird. Die meisten Studien belegen nur diese Korrelation ohne Kausalitätsnachweis. Ergebnisse der neurobiologischen Forschung weisen auf die Nähe von ADHS und Mediensucht hin. Schlussfolgerungen: Bei Diagnose einer ADHS muss insbesondere auch die Mediennutzung erfasst werden und bei Vorliegen einer Mediensucht sorgfältig auf ADHS untersucht werden. ADHS muss als Risikofaktor für die Entwicklung einer Mediensucht angesehen werden, adäquate Therapie der ADHS kann dieses Risiko verringern. Eine ausgedehnte Mediennutzung kann Hinweis auf eine ungenügend behandelte ADHS sein.

Gap Effect Abnormalities during a Visually Guided Pro-Saccade Task in Children with Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that starts in early childhood and has a comprehensive impact on psychosocial activity and education as well as general health across the lifespan. Despite its prevalence, the current diagnostic criteria for ADHD are debated. Saccadic eye movements are easy to quantify and may be a quantitative biomarker for a wide variety of neurological and psychiatric disorders, including ADHD. The goal of this study was to examine whether children with ADHD exhibit abnormalities during a visually guided pro-saccadic eye-movement and to clarify the neurophysiological mechanisms associated with their behavioral impairments. Thirty-seven children with ADHD (aged 5–11 years) and 88 typically developing (TD) children (aged 5–11 years) were asked to perform a simple saccadic eye-movement task in which step and gap conditions were randomly interleaved. We evaluated the gap effect, which is the difference in the reaction time between the two conditions. Children with ADHD had a significantly longer reaction time than TD children (p < 0.01) and the gap effect was markedly attenuated (p < 0.01). These results suggest that the measurement of saccadic eye movements may provide a novel method for evaluating the behavioral symptoms and clinical features of ADHD, and that the gap effect is a potential biomarker for the diagnosis of ADHD in early childhood.

KCNIP4 as a candidate gene for personality disorders and adult ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder in children with striking persistence into adulthood and a high co-morbidity with other psychiatric disorders, including personality disorders (PD). The 4p15.31 region was shown to be associated with ADHD in several genome wide association studies (GWAS). In the present study we also report association of the 4p15.31 locus with Cluster B and Cluster C PD as identified by a pooled genome-wide association study in 400 individuals suffering from PD. The gene coding for the Kv channel-interacting protein 4 (KCNIP4) is located in this region. KCNIP4 is an interaction partner of presenilin and plays a role in a negative feedback loop in the Wnt/β-catenin pathway. Thus, we reasoned it to be a promising candidate gene for ADHD as well as for PD. To clarify the role of KCNIP4 in those disorders, we conducted candidate gene based association studies in 594 patients suffering from adult ADHD and 630 PD patients as compared to 974 healthy control individuals. In the adult ADHD sample, six single markers and one haplotype block revealed to be associated with disease (p values from 0.0079 to 0.049). Seven markers within the KCNIP4 gene showed an association with PD (p values from 0.0043 to 0.0437). The results of these studies suggest a role of KCNIP4 in the etiology of ADHD, PD and other co-morbid disorders.

[Association of atopic eczema and attention-deficit/hyperactivity disorder - meta-analysis of epidemiologic studies]

BACKGROUND

Atopic dermatitis (AD) and attention-deficit/hyperactivity disorder (ADHD) are frequent paediatric conditions with high medical relevance. A possible relationship between atopic diseases (i.e., AD, asthma, and allergic rhinitis) has long been discussed, but convincing evidence is still missing.

METHODS

We investigated the relationship between AD and ADHD in two cross-sectional studies and in two birth cohort studies considering lifestyle factors, environmental factors, and atopic comorbidities as potential confounders. To quantify the strength of association between AD and ADHD, data from the four epidemiologic studies were summarized by means of a meta-analysis. Odds ratios (OR) were pooled for the association between prevalent or previous AD and prevalent ADHD from the four studies adjusted for age, sex, and atopic comorbidity (allergic rhinitis, asthma).

RESULTS

The epidemiologic studies conducted consistently indicate an association between AD and ADHD which is independent of environmental exposures and other comorbidities. Particularly infant AD appears to be associated with later development of ADHD symptoms. Sleeping problems due to AD are suggested as playing an important role for the observed association between AD and ADHD. The pooled OR (95 % confidence interval (95 %CI)) for the association between AD and ADHD was 1.43 (1.25-1.64).

DISCUSSION

Four new epidemiologic studies consistently indicate a positive association between AD and ADHD. Compared to children without AD, children with previous or prevalent AD have an approximately 43 % increased risk to be diagnosed with ADHD or to display clinical ADHD symptoms. Following our findings, the biological mechanisms underlying the observed comorbidity between AD and ADHD require further investigation in order to subsequently develop targeted therapeutic and preventive strategies.

Association of APC and REEP5 gene polymorphisms with major depression disorder and treatment response to antidepressants in a Han Chinese population

OBJECTIVE

Despite the high prevalence of depression and its considerable impact on the population, knowledge about the pathogenesis of the illness and the antidepressant treatment response is still unknown.

METHODS

A total of 397 patients with major depression disorder (MDD) and 473 normal controls were employed in the present research. Twelve single nucleotide polymorphisms (SNPs) within the adenomatous polyposis coli (APC) and receptor accessory protein (REEP5) genes were selected for genotyping using the GoldenGate genotyping assay. A total of 165 MDD patients completed a 6-week antidepressant treatment. Responders were defined as patients with at least a 50% reduction in Hamilton Rating Scale for Depression total scores posttreatment.

RESULTS

Two SNPs (rs2464805 and rs563556) within the APC gene exhibited a statistically significant association with MDD when analyzed by genotype and allele frequencies. Three SNPs (rs495794, rs153549 and rs153560) in the REEP5 gene showed significant statistical differences between the responders and nonresponders.

CONCLUSIONS

The APC gene may be one of the susceptibility genes for MDD as well as a genetic link between psychiatric disease and cancer. REEP5 gene polymorphisms may influence antidepressant treatment response in MDD.

Altered mRNA expression of monoaminergic candidate genes in the blood of children with attention deficit hyperactivity disorder and autism spectrum disorder

OBJECTIVES

In absence of objective clinical characteristics the identification of peripheral biomarkers in neuropsychiatric disorders is highly relevant for the diagnostic process and an individualized therapy. We analyzed mRNA-expression of monoaminergic candidate genes (DRD4, DRD5, TPH1) in peripheral tissue of patients with attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD), highly comorbid with ADHD, searching for possible molecular markers for these disorders.

METHODS

mRNA was obtained from children and adolescents with ADHD (n = 51) and ASD (n = 26), diagnosed according to ICD-10 criteria, as well as healthy controls (n = 39). mRNA expression was determined via quantitative realtime PCR (qRT-PCR) from whole blood cells.

RESULTS

The concentrations of DRD4-mRNA in the whole blood were significantly lower in ADHD and ASD children (19 of 26 comorbid with ADHD) compared to healthy controls. ASD patients revealed a significantly decreased DRD5 mRNA expression in comparison to the two other groups.

CONCLUSIONS

Alterations in mRNA expression patterns provide further evidence for a relevant effect of the respective candidate genes in the pathophysiology of ADHD. Given their potential as biomarkers mRNA expression patterns may be useful tools in (differential-) diagnostic procedures of ADHD and ASD. Future studies may determine the sensitivity and specificity of these putative biomarkers in larger samples including further neuropsychiatric diagnoses.

Restless legs syndrome as a possible predictor for psychiatric disorders in parents of children with ADHD

Attention-deficit hyperactivity disorder (ADHD) is a common disorder with estimated prevalence of 5% in children and 3.4% in adults. Psychiatric disorders are a frequent concomitant feature. Restless legs syndrome (RLS) may mimic the symptoms of ADHD. The aim of the study is to evaluate whether the presence of RLS predicts occurrence of psychiatric disorders in parents of children with ADHD. Thirty-seven parents of 26 children with ADHD were examined for RLS and for lifetime prevalence rates of psychiatric disorders and personality disorders based on the Structured Clinical Interview for DSM-IV Diagnoses (SCID). Prevalence rates in parents were 29.7% for RLS, 67.6% for Axis I and 40.5% for Axis II disorders. Mothers revealed higher rates for depression, anxiety disorders and ADHD than fathers, whereas personality disorders occurred at higher rates in fathers. The presence of RLS predicted a diagnosis of ADHD (odds ratio (OR) 21.9), agoraphobia (OR = 20.4) and any anxiety disorder (OR = 8.5). Although limited by the small sample size, we found evidence for increased rates of cluster B personality disorders (OR = 59.3) in parents with RLS. All parents of the latter group (100%) reported a positive family history of psychiatric disorders which was not the case in parents without RLS (69.2%) excluding the index children with ADHD. RLS seems to indicate increased vulnerability for psychiatric disorders, i.e., ADHD and anxiety disorders, in a subgroup of parents from ADHD children. Synaptic dysfunction affecting dopaminergic transmission among other transmitter systems may be a common final pathway related to the phenotypic spectrum of ADHD.

[Forensic psychiatry in the era of neuroscience: present status and outlook for neurobiological research]

Progress in neurobiological research has influenced our view of human beings and the basics of their behavior. Regarding criminal law and forensic psychiatry, established codes of practice are being challenged by neuroscientific research. This article gives an overview of neurobiological findings and methods in the context of forensic psychiatric issues. Empirical approaches to addressing important legal questions are outlined. Principles behind forensic psychiatric expert opinions are given. The effect and future of neuroscientific findings and methods in answering forensic psychiatric questions are discussed. Limitations and legal and ethical requirements are addressed.

Molecular genetics of adult ADHD: converging evidence from genome-wide association and extended pedigree linkage studies

A genome-wide association (GWA) study with pooled DNA in adult attention-deficit/hyperactivity disorder (ADHD) employing approximately 500K SNP markers identifies novel risk genes and reveals remarkable overlap with findings from recent GWA scans in substance use disorders. Comparison with results from our previously reported high-resolution linkage scan in extended pedigrees confirms several chromosomal loci, including 16q23.1-24.3 which also reached genome-wide significance in a recent meta-analysis of seven linkage studies (Zhou et al. in Am J Med Genet Part B, 2008). The findings provide additional support for a common effect of genes coding for cell adhesion molecules (e.g., CDH13, ASTN2) and regulators of synaptic plasticity (e.g., CTNNA2, KALRN) despite the complex multifactorial etiologies of adult ADHD and addiction vulnerability.