Monday, August 28, 2006

ADHD (attention deficit hyperactivity disorder): Clinical Psychology Review special articles

In reviewing this weeks "recent literature of interest" I noticed that the journal Clinical Psychology Review had recently published a special issue on ADHD. In addition, I noticed another issue of CPR that included an interesting ADHD/MR article, as well as an article "in press" dealing with ADHD and interventions. Below are the titles of the articles and abstracts. I've included a link to a copy of the pdf file for the editorial introduction to the special issue.

CPR Special Issue

Attention deficit hyperactivity disorder from a neurosciences and behavioral approach: An introduction. EDITORIAL. Clinical Psychology Review (2006), 26 Pages 377-378. Julie B. Schweitzer (link)

1. Behavioral models of impulsivity in relation to ADHD: Translation between clinical and preclinical studies • Pages 379-395. Catharine A. Winstanley, Dawn M. Eagle and Trevor W. Robbins
  • Impulsivity, broadly defined as action without foresight, is a component of numerous psychiatric illnesses including attention deficit/hyperactivity disorder (ADHD), mania and substance abuse. In order to investigate the mechanisms underpinning impulsive behavior, the nature of impulsivity itself needs to be defined in operational terms that can be used as the basis for empirical investigation. Due to the range of behaviors that the term impulsivity describes, it has been suggested that impulsivity is not a unitary construct, but encompasses a variety of related phenomena that may differ in their biological basis. Through fractionating impulsivity into these component parts, it has proved possible to devise different behavioral paradigms to measure various aspects of impulsivity in both humans and laboratory animals. This review describes and evaluates some of the current behavioral models of impulsivity developed for use with rodents based on human neuropsychological tests, focusing on the five-choice serial reaction time task, the stop-signal reaction time task and delay-discounting paradigms. Furthermore, the contributions made by preclinical studies using such methodology to improve our understanding of the neural and neurochemical basis of impulsivity and ADHD are discussed, with particular reference to the involvement of both the serotonergic and dopaminergic systems, and frontostriatal circuitry.
2. The genetics of attention deficit hyperactivity disorder. Pages 396-432. Irwin D. Waldman and Ian R. Gizer
  • Over the past 15 years, considerable progress has been made in understanding the etiology of childhood Attention Deficit Hyperactivity Disorder (ADHD), largely due to the publication of numerous twin studies which are consistent in suggesting substantial genetic influences (i.e., heritabilities ranging from 60% to 90%), non-shared environmental influences that are small-to-moderate in magnitude (i.e., ranging from 10% to 40%), and little-to-no shared environmental influences. Following from these quantitative genetic findings, numerous molecular genetic studies of association and linkage between ADHD and a variety of candidate genes have been conducted during the past 10 years. The majority of the candidate genes studied underlie various facets of the dopamine, norepinephrine, and serotonin neurotransmitter systems, although the etiological role of candidate genes outside of neurotransmitter systems (e.g., involved in various aspects of brain and nervous system development) have also been examined. In this paper, we review recent findings from candidate gene studies of childhood ADHD and highlight those candidate genes for which associations are most replicable and which thus appear most promising. We conclude with a consideration of some of the emerging themes that will be important in future studies of the genetics of ADHD.
3. Brain development and ADHD. Pages 433-444. Amy L. Krain and F. Xavier Castellanos
  • Attention-Deficit/Hyperactivity Disorder (ADHD) is characterized by excessive inattention, hyperactivity, and impulsivity, either alone or in combination. Neuropsychological findings suggest that these behaviors result from underlying deficits in response inhibition, delay aversion, and executive functioning which, in turn, are presumed to be linked to dysfunction of frontal–striatal–cerebellar circuits. Over the past decade, magnetic resonance imaging (MRI) has been used to examine anatomic differences in these regions between ADHD and control children. In addition to quantifying differences in total cerebral volume, specific areas of interest have been prefrontal regions, basal ganglia, the corpus callosum, and cerebellum. Differences in gray and white matter have also been examined. The ultimate goal of this research is to determine the underlying neurophysiology of ADHD and how specific phenotypes may be related to alterations in brain structure.
4. Is there evidence for neural compensation in attention deficit hyperactivity disorder? A review of the functional neuroimaging literature. Pages 445-465. Catherine Fassbender and Julie B. Schweitzer
  • This article reviews evidence for the presence of a compensatory, alternative, neural system and its possible link to associated processing strategies in children and adults with attention deficit hyperactivity disorder (ADHD). The article presents findings on a region by region basis that suggests ADHD should be characterized not only by neural hypo-activity, as it is commonly thought but neural hyperactivity as well, in regions of the brain that may relate to compensatory brain and behavioral functioning. In this context studies from the functional neuroimaging literature are reviewed. We hypothesize that impaired prefrontal (PFC) and anterior cingulate (ACC) cortex function in ADHD reduces the ability to optimally recruit subsidiary brain regions and strategies to perform cognitive tasks. The authors conclude that healthy individuals can recruit brain regions using visual, spatial or verbal rehearsal for tasks as needed. In contrast, individuals with ADHD may be less able to engage higher order executive systems to flexibly recruit brain regions to match given task demands. This may result in greater reliance on neuroanatomy that is associated with visual, spatial, and motoric processing rather than verbal strategies. The authors speculate that this impaired flexibility in recruiting brain regions and associated strategies limits adaptation to new cognitive demands as they present and may require more effortful processing.
5. Neuropsychological functioning in people with ADHD across the lifespan. Pages 466-485. Larry J. Seidman
  • ADHD is defined by behavioral characteristics similar to neuropsychological disorders of executive dysfunction. This paper is a literature review of the neurocognitive characteristics of ADHD from early childhood through adulthood. The author addresses the development of the concept of attention and executive function (EF) deficits in ADHD, clinical neuropsychological studies of pre-teenage children, teenagers and adults with ADHD, gender and the role of psychiatric co-morbidity including the relationship of learning disabilities to ADHD, heterogeneity of neuropsychological dysfunctions, experimental neuropsychological studies, the relationship of brain structure to function, psychopharmacology of ADHD, and clinical neuropsychological assessment. The group data clearly supports the hypothesis that executive dysfunctions are correlates of ADHD regardless of gender and age, and these EF deficits are exacerbated by co-morbidity with learning disabilities such as dyslexia. However, there is limited data on children under the age of 5, teenagers from age 13–18, and adults with ADHD over the age of 40. Studies of individual classification of people with ADHD compared to healthy, non-psychiatric controls do not support the use of neuropsychological tests for the clinical diagnosis of ADHD, and indicate that not all persons with ADHD have EF deficits. Some persons with ADHD may have deficits in brain reward systems that are relatively independent of EF impairments. Future research should clarify the multiple sources of ADHD impairments, continue to refine neuropsychological tools optimized for assessment, and incorporate longitudinal, developmental designs to understand ADHD across the lifespan.

6. Evidence-based psychosocial treatments for children and adolescents with attention-deficit/hyperactivity disorder. Pages 486-502. Andrea M. Chronis, Heather A. Jones and Veronica L. Raggi

  • Despite the vast literature supporting the efficacy of stimulant medication in the treatment of attention-deficit/hyperactivity disorder (ADHD), several limitations of pharmacological treatments highlight the clear need for effective psychosocial treatments to be identified. A large evidence base exists for behavioral interventions, including parent training and school interventions, which has resulted in their classification as “empirically validated treatments.” Additionally, social skills training with generalization components, intensive summer treatment programs, and educational interventions appear promising in the treatment of ADHD. Given the chronic impairment children with ADHD experience across multiple domains of functioning, multimodal treatments are typically necessary to normalize the behavior of these children. The state of the ADHD treatment literature is reviewed, important gaps are identified (e.g., treatment for adolescents), and directions for future research are outlined within a developmental psychopathology framework.

Two other CPR ADHD-related articles

Is ADHD a valid disorder in children with intellectual delays? Kevin M. Antshel, Margaret H. Phillips, Michael Gordon, Russell Barkley, Stephen V. Faraone. Clinical Psychology Review 26 (2006) 555–572
  • To assess the validity of ADHD in children with mental retardation, we applied Robins and Guze's [Robins, E., and Guze, S.B.(1970). Establishment of diagnostic validity in psychiatric illness: Its application to schizophrenia. American Journal of Psychiatry, 126, 983–987.] criteria for determining the validity of a psychiatric disorder. We review the literature describing clinical correlates, family history, treatment response, laboratory studies, course, and outcome of children with ADHD and mental retardation. Although clearly an area in need of further research, there is preliminary evidence to suggest that ADHD is a valid psychiatric condition in children with mental retardation. Nevertheless, without knowing the base rates of ADHD symptoms in the mental retardation population, the positive predictive power and negative predictive power of ADHD symptoms in this population remain an open question. In addition to assessment of base rate symptoms, future research should consider what diagnostic algorithm may best be applied to the diagnosis of ADHD in mental retardation.
Social incompetence in children with ADHD: Possible moderators and mediators in social-skills training Gerly M. de Boo, Pier J.M. Prins. Clinical Psychology Review (2006, in press)
  • Children with attention-deficit/hyperactivity disorder (ADHD) often encounter problems in social interactions with peers and are confronted with peer rejection and social isolation. The most common approach to social problems in children is social skills training. This intervention concept represents a variable mixture of cognitive-behavioral intervention elements. In this article the outcome of social skills training (SST) for children with ADHD is reviewed. Four experimental SSTs are detected and analyzed for potential mediators and moderators of treatment efficacy. Candidate mediators (social cognitive skills, parenting style and medication-induced reduction of key symptoms) are discussed within an empirical and theoretical context. Candidate moderators (subtype, comorbidity, gender and age) are evaluated for their empirical support. It is argued that, although fragmented, there is ample evidence and knowledge to adapt the SST-paradigm towards the specific needs of children suffering from ADHD and to guide future research towards more effective, “well established” interventions.
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