Genetics of attention deficit hyperactivity disorder

Results of behavioral genetic and molecular genetic studies have converged to suggest that both genetic and nongenetic factors contribute to the development of attention deficit hyperactivity disorder (ADHD). Family, twin, and adoption studies provide compelling evidence that genes play a strong role in mediating susceptibility to ADHD. In contrast to a handful of genome-wide scans conducted thus far, many candidate gene studies of ADHD have produced substantial evidence implicating several genes in the etiology of the disorder. Yet, even these associations are small and consistent with the idea that the genetic vulnerability to ADHD is mediated by many genes of small effects. These small effects emphasize the need for future candidate gene studies to implement strategies that will provide enough statistical power to detect such small effects.     

Gait in attention deficit hyperactivity disorder

Abstract Background Cognitive function and the loading of attention presumably play an important role in gait as well as in fall risk, but previous work has not demonstrated this in any cause-and-effect way. Objectives To gain insight into the relationship between gait and cognitive function, we sought: (1) To compare the gait rhythmicity (stride time variability) of children with attention deficit hyperactivity disorder (ADHD) to controls, (2) To test the hypothesis that dual tasking leads to increased stride-to-stride variability in ADHD, and (3) To test whether pharmacological treatment that relieves ADHD symptoms reduces stride-to-stride variability. Patients and Methods Gait was quantified in children with ADHD and in age-matched healthy controls under single task and dual task conditions on three occasions: off medications (both groups) and, in the ADHD group, after double blinded, randomized administration of methylphenidate (MPH) or placebo. Results At baseline, children with ADHD tended to walk with increased stride-to-stride variability compared to the controls during the single task condition (p = 0.09). During dual task walking, stride time variability was significantly reduced in the children with ADHD (p < 0.004), but not in the controls. In the children with ADHD, the placebo did not significantly affect stride-to-stride variability or the dual tasking response. In contrast, stride time variability was significantly reduced on MPH (p < 0.001) such that dual tasking no longer affected variability. Conclusions The present findings demonstrate alterations in the gait of children with ADHD, support a cause and effect link between cognitive function and gait, and suggest that enhancement of attention abilities may, in certain populations, improve gait rhythmicity.     

Genes and attention deficit hyperactivity disorder

The initial molecular genetic studies of attention deficit hyperactivity disorder (ADHD) evaluated two candidate genes (DAT and DRD4) suggested by dopamine theories of this common disorder and its treatment with stimulant medication. The initial reports of weak associations with ADHD have been replicated by many (but not all) investigators, as is expected for genes with small effects. This literature is reviewed, along with emerging literature generated by active research groups investigating additional genes that might contribute to the genetic basis of this complex disorder.     

Multicomponent attention deficits in attention deficit hyperactivity disorder

The aim of this study was to examine the specific aspects of attention, such as selective attention, sustained attention, and short-term memory in children with attention deficit hyperactivity disorder, combined subtype (ADHD-C). A total of 40 children with a diagnosis of ADHD from the 4th edition of the Diagnostic and Statistical Manual, aged 6-11 years old were compared with 40 controls matched for age and gender on a battery of tests. Short-term memory span and attention was measured by Visual Aural Digit Span Test-Revised. Stroop test and the Turkish version of Cancellation Test were used to assess selective and sustained attention, respectively. In order to check for factor structure in two groups on the test scores, principal component analysis was conducted for both groups separately. Relative to the comparison children, children with ADHD showed significant deficits on tests that are related to different aspects of attention. The results are consistent with the theories explaining the biological basis of ADHD by scattered attention networks in the brain, which have reciprocal dynamic interactions. Further comparative studies are needed to elucidate whether the cognitive processes that are known to be assessed by these tests are specific to ADHD.     

Neuroendocrine aspects of attention deficit hyperactivity disorder

This article summarizes the existing neuroendocrine literature and reports the growth hormone response to stimulation with L-dopa and clonidine in male children and adolescents with attention deficit hyperactivity disorder. Because growth hormone secretion is regulated by monoamine neurotransmitters, hyposecretion of growth hormone may reflect generalized changes in the neurochemical substrate of this disorder. With refinement, these neuroendocrine challenge tests may become unique biologic markers in identifying attention deficit hyperactivity disorder in children and adolescents.     

Atypical outcome in attention deficit hyperactivity disorder

This report describes the course of psychiatric illness in two boys. Both presented with attention deficit hyperactivity disorder (ADHD) in midchildhood; after puberty, one boy developed a schizophrenic illness while the other boy developed a major affective illness. Although the major ADHD outcome studies have found no link between the childhood occurrence of ADHD and psychosis in adulthood, occasionally such a link may exist. The theoretical and practical implications of this finding are discussed. It should be noted, however, that such outcome is highly atypical and very rare.     

Genetic influences on attention deficit hyperactivity disorder

In this article we review behavioral and molecular genetics studies of attention deficit hyperactivity disorder (ADHD). Family, twin, and adoption studies, along with segregation analyses and molecular genetic studies, all support the hypothesis that both genetic and environmental factors contribute to the etiology of ADHD. Despite this strong evidence for the familial transmission of ADHD, the mode of transmission requires further clarification. In addition, because ADHD appears to be genetically heterogeneous, more work is needed to delineate genetically homogeneous subtypes and describe the range of expression of their underlying genotypes.     

Psychosocial interventions in attention deficit hyperactivity disorder

This brief overview of psychosocial treatment approaches to attention deficit hyperactivity disorder (ADHD) concentrates on the two that receive the greatest research support, parent training in child behavior management and teacher training in classroom management. Cognitive-behavioral training of children who have ADHD has little evidence of efficacy and group social skills training has mixed or limited evidence of effectiveness. Research should focus on more theoretically driven psychosocial treatment approaches, on potential side effects or adverse events associated with this form of intervention, and on the complex pathways that affect impairment in major life activities that could guide subsequent treatment design for such impairments.     

Raising attention to attention deficit hyperactivity disorder in schizophrenia

Schizophrenia and attention deficit hyperactivity disorder (ADHD) are two psychiatric disorders with a negative impact on quality of life of individuals affected. Although they are classified into distinct disorders categories, attentional dysfunction is considered as a core feature in both conditions, either at the clinical then pathophysiological level. Beyond the obvious clinical overlap between these disorders, the Research Domain Criteria approach might offer an interesting perspective for disentangling common circuits underpinning both disorders. Hence, we review evidences regarding the overlap between schizophrenia and ADHD, at the clinical level, and at the level of underlying brain mechanisms. The evidence regarding the influence of environmental risk factors in the emergence of both disorders, and their developmental trajectories is also reviewed. Among these, we will try to elucidate the complex relationship between stimulants use and psychotic symptoms, discussing the potential role of ADHD medication in inducing psychosis or in exacerbating it. We aim that, taken together, these findings may promote further investigation with important implications both for clinicians and research. In fact, considering the amounting evidence on the overlap between schizophrenia and ADHD, the delineation of their boundaries might help in the decision for diagnosis and treatment. Moreover, it may help to promote interventions focused on the prevention of both schizophrenia and ADHD, by the reduction of recognized environmental risk factors.     

Frontiers between attention deficit hyperactivity disorder and bipolar disorder

The co-occurrence of attention deficit hyperactivity disorder (ADHD) and bipolar disorder has received much recent attention in the literature. The authors review the literature examining associations between ADHD and bipolar disorder in children, and data concerning severe irritability in youth with ADHD. This article focuses on (1) population-based studies examining ADHD and bipolar disorder or ADHD and co-occurring irritability, (2) the co-occurrence and prospective relationships of ADHD and bipolar disorder in clinical samples, (3) phenomenology and assessment of bipolar disorder and ADHD, (4) treatment of comorbid ADHD and bipolar disorder, (5) family and genetic studies of ADHD and bipolar disorder, and (6) pathophysiologic comparisons between children with ADHD and irritability and bipolar disorder. We draw on the research to make clinical recommendations and highlight important directions for future research.     

注意缺陷多动障碍遗传学研究

注意缺陷多动障碍(Attention- deficit hyperactivity disorder,ADHD)是一种遗传性疾病,多与儿童行为障碍、酒精依赖、物质滥用、社会紊乱型人格障碍和情感障碍等共病.目前发现ADHD的某些症状,与孤独症类似.对双胞胎和家庭的研究发现其具有很高程度的遗传度,而与家庭环境基本无关.     

Psychotherapy of attention deficit hyperactivity disorder in adults

In clinical practice many adult patients with attention deficit hyperactivity disorder (ADHD) ask for an additional psychotherapeutic intervention besides the medical therapy. In this paper we present a structured skill training program particularly tailored for adult patients with ADHD. The program is based on the principles of cognitive-behavioral treatment for borderline personality disorder developed by M. Linehan. It was modified to suit the special needs of adult patients with ADHD. In this exploratory pilot study we tested this program in a group setting. The following elements were presented: neurobiology of ADHD, mindfulness, chaos and control, behavior analysis, emotion regulation, depression, medication in ADHD, impulse control, stress management, dependency, ADHD in relationship and self respect. In an open study design patients were assessed clinically using psychometric scales (Attention Deficit Hyperactivity Disorder Checklist according to DSM-IV, 16 items of the SCL-90-R, Beck-Depression Inventory, visual analogue scale) prior to and following group therapy. This treatment resulted in positive outcomes in that patients improved on all psychometric scales. Received: 19 April 2002 / Accepted: 18 July 2002     

Treatment of attention deficit hyperactivity disorder in children

Objective The present study investigated the predictive power of anxiety, IQ, severity of ADHD and parental depression on the outcome of treatment in children with ADHD. Method Fifty children with ADHD (ages 8–12) were randomized to a 10-week treatment of methylphenidate or to a treatment of methylphenidate combined with multimodal behavior therapy. Prior to treatment predictors were assessed. Outcome was assessed separately for parents and teachers on a composite measure of inattentive, hyperactive, oppositional- and conduct disorder symptoms. Results There was neither a significant difference between the two treatments at baseline nor did treatment condition predict outcome. Therefore the data were collapsed across the two treatments. A combination of anxiety and IQ predicted teacher-rated outcome, explaining 18% of the variance. Higher anxiety and higher IQ’s indicated better treatment outcome. There were no significant predictors of the parent-rated outcome. Conclusion This study showed a small but significant predictive effect of IQ and anxiety on treatment outcome in children with ADHD. Clinical implications This study supports the idea that for the treatment of ADHD children with comorbid anxiety and higher IQ respond better to the two most used treatments for ADHD.     

Treatment of attention deficit hyperactivity disorder in adults

A number of medication and psychologic treatment options for adults with attention deficit hyperactivity disorder have become available during the past 5 years, while others are under investigation. This review describes the safety and effectiveness of the stimulants (i.e., methylphenidate and dexedrine), and particularly the newer long-acting stimulants (i.e., Concerta) and Adderall XR) in the treatment of this population. Some nonstimulant/nonantidepressants, particularly atomoxetine, have also been shown to improve attention deficit hyperactivity disorder symptoms. Combination treatment of stimulants and antidepressants require more study with regard to safety and efficacy. Psychosocial interventions (e.g., cognitive behavioral therapy, mindfulness training and cognitive remediation) can also benefit adults with attention deficit hyperactivity disorder. Cognitive behavioral therapy combined with medication is more effective than either intervention alone, especially for addressing the emotional and functional aspects of peoples lives and thus improving occupational, interpersonal and emotional outcomes.     

Pharmacologic treatment of attention deficit hyperactivity disorder.

This article describes the role of psychostimulant medication in the treatment of attention deficit hyperactivity disorder. Included are the drugs' putative mechanisms of action, pharmacology, toxicology, indications for their use, short-term and long-term actions, adverse effects, specific dosing regimens, therapeutic monitoring techniques, alternative medications, and drug interactions.     

注意缺陷多动障碍的分子遗传学进展

注意缺陷多动障碍（attention deficit hyperactivity disorder,ADHD）是常见的神经精神疾病,严重影响儿童、青少年和成人的学业、社交和工作技能。目前,儿童和青少年的患病率约为6％～9％。家系研究、双生子和寄养子研究结果显示遗传因素是ADHD的重要发病因素,平均遗传度约为76％。但是,ADHD病因与临床表现复杂,同时具有个体差异性,至今尚未阐明ADHD发病的生物学机制。对ADHD发病机制的分子遗传学研究主要集中于功能候选基因的关联分析领域。     

Sustained attention in sensory modulation disorder and attention deficit/hyperactivity disorder

BackgroundThere are high comorbidity rates between sensory modulation disorder (SMD) and attention deficit hyperactivity disorder (ADHD). Knowledge regarding the objective neuropsychological differentiation between them is scarce.AimThis study examines the effects of SMD and ADHD on a sustained attention task with and without aversive auditory conditions.MethodSixty six young adult females were tested on the Conjunctive - Continuous Performance Task-Visual (CCPT-V) measuring sustained attention, under two conditions: 1) aversive condition (with the three most aversive sounds chosen by the participant), and 2) non-aversive condition (without sounds).ResultsBoth the SMD and ADHD factors exhibited performance deficits in the sustained attention task. All study participants performed worse on both sustained attention and speed of processing when aversive sounds were present.ConclusionWe conclude that impaired sustained attention cannot differentiate between SMD and ADHD. Hence, these results should be taken under consideration in the assessment process of ADHD vs. SMD.