Etiologic Subtypes of Attention-Deficit/Hyperactivity Disorder: Brain Imaging, Molecular Genetic and Environmental Factors and the Dopamine Hypothesis

Multiple theories of Attention-Deficit/Hyper- activity Disorder (ADHD) have been proposed, but one that has stood the test of time is the dopamine deficit theory. We review the narrow literature from recent brain imaging and molecular genetic studies that has improved our understanding of the role of dopamine in manifestation of symptoms of ADHD, performance deficits on neuropsychological tasks, and response to stimulant medication that constitutes the most common treatment of this disorder. First, we consider evidence of the presence of dopamine deficits based on the recent literature that (1) confirms abnormalities in dopamine-modulated frontal-striatal circuits, reflected by size (smaller-than-average components) and function (hypoactivation); (2) clarifies the agonist effects of stimulant medication on dopaminergic mechanisms at the synaptic and circuit level of analysis; and (3) challenges the most-widely accepted ADHD-related neural abnormality in the dopamine system (higher-than-normal dopamine transporter [DAT] density). Second, we discuss possible genetic etiologies of dopamine deficits based on recent molecular genetic literature, including (1) multiple replications that confirm the association of ADHD with candidate genes related to the dopamine receptor D4 (DRD4) and the DAT; (2) replication of differences in performance of neuropsychological tasks as a function of the DRD4 genotype; and (3) multiple genome-wide linkage scans that demonstrate the limitations of this method when applied to complex disorders but implicate additional genes that may contribute to the genetic basis of ADHD. Third, we review possible environmental etiologies of dopamine deficits based on recent studies of (1) toxic substances that may affect the dopamine system in early development and contribute substantially to the etiology of ADHD; (2) fetal adaptations in dopamine systems in response to stress that may alter early development with lasting effects, as proposed by the developmental origins of health and disease hypothesis; and (3) gene-environment interactions that may moderate selective damage or adaptation of dopamine neurons. Based on these reviews, we identify critical issues about etiologic subtypes of ADHD that may involve dopamine, discuss methods that could be used to address these issues, and review old and new theories that may direct research in this area in the future.     

Attention-Deficit/Hyperactivity Disorder: A Neuropsychological Perspective Towards DSM-V

Neuropsychological methods and techniques have much to offer in the evaluation of the individual suspected as having Attention-Deficit/Hyperactivity Disorder (ADHD). After a review of the historical evolution of the ADHD concept, incidence and prevalence, and DSM-IV criteria for diagnosis, especially as regards omission related to gender differences, and other associated cultural, familial, socioenvironmental, and subject influences, this paper describes a number of dilemmas and obstacles encountered in clinical practice. Included are the confounds associated with the wide range of possible comorbidities, the insufficiency of current DSM-IV criteria, the emergence of subtype differentiation and its impact on diagnosis and treatment. The complex relationship between neuropsychological constructs and ADHD, and obstacles to valid assessment are also addressed. The complexities associated with a thorough ADHD evaluation are viewed within an impressive and expansive existing scientific framework and recommendations are made for future directions.     

Romantic Relationships and Health: An Examination of Individuals’ Perceptions of their Romantic Partners’ Influences on their Health

This study examines individuals’ perceptions of the impact their significant others have on their health and the extent to which these perceptions are associated with relationship quality and actual health. Two-hundred and ten participants (105 U.S. couples; mean age = 24.93) completed measures of their relationship quality and health along with an open-ended measure asking them to indicate how they felt their partner influenced their health. Results indicated that participants perceived their romantic partners to be primarily positive health influences, women believed their partners were more influential than did men, and eating and physical activity behaviors were believed to be most affected by partners. Participants’ relationship quality and health were associated with their reports of their perceived partners’ health influences. The research described in this report was supported by an award to Charlotte Markey from Rutgers University.     

Changing perspective within and across environments

Perspective change within a single environment is a slow and effortful process. However, little research has addressed perspective change across multiple environments. Using a task-set switching paradigm, subjects judged spatial relationships between target locations from differing perspectives. Response times were longer when successive trials probed different perspectives. However, this cost was greater when perspective was changed within a single environment compared to when it was changed across two environments. This result indicates that the processing of perspective change, and perhaps general spatial reasoning, differs in these two cases. Implications for theories of perspective change and environmental knowledge are discussed.     

Peer Contagion in Interventions for Children and Adolescents: Moving Towards an Understanding of the Ecology and Dynamics of Change

The influence of deviant peers on youth behavior is of growing concern, both in naturally occurring peer interactions and in interventions that might inadvertently exacerbate deviant development. The focus of this special issue is on understanding the moderating and mediating variables that account for peer contagion effects in interventions for youth. This set of nine innovative papers moves the field forward on three fronts: (1) Broadening the empirical basis for understanding the conditions under which peer contagion is more or less likely (that is, moderators of effects); (2) Identifying mechanisms that might account for peer contagion effects (mediators); and (3) Forging the methodological rigor that is needed to study peer contagion effects within the context of intervention trials. We propose an ecological framework for disentangling the effects of individuals, group interactions, and program contexts in understanding peer contagion effects. Finally, we suggest methodological enhancements to study peer contagion in intervention trials.     

Switching between environmental representations in memory

In everyday life we accomplish tasks that require the storage and access of mental representations of different environments that we are not currently perceiving. Past research has suggested that environments are encoded by a series of independent representations that are organized in memory. Three experiments tested this idea further by asking whether multiple representations of environments can be accessed simultaneously. Using a cued task-set switching paradigm, subjects judged spatial relationships between target locations in two familiar environments. Response times were longer when successive trials probed different environments, an effect not due to switching between semantic categories or semantic priming, suggesting that representations of environments are accessed sequentially. Implications for various hypotheses concerning the properties of environmental representations are discussed.     

Reducing Youth Access to Alcohol: Findings from a Community-Based Randomized Trial

Underage drinking continues to be an important public health problem and a challenge to the substance abuse prevention field. Community-based interventions designed to more rigorously control underage access to alcohol through retailer education and greater enforcement of underage drinking laws have been advocated as potentially effective strategies to help address this problem, but studies designed to evaluate such interventions are sparse. To address this issue we conducted a randomized trial involving 36 communities to test the combined effectiveness of five interrelated intervention components designed to reduce underage access to alcohol. The intervention was found to be effective in reducing the likelihood that retail clerks would sell alcohol to underage-looking buyers, but did not reduce underage drinking or the perceived availability of alcohol among high school students. Post hoc analyses, however, revealed significant associations between the level of underage drinking law enforcement in the intervention communities and reductions in both 30-day use of alcohol and binge drinking. The findings highlight the difficulty in reducing youth drinking even when efforts to curtail retail access are successful. Study findings also suggest that high intensity implementation of underage drinking law enforcement can reduce underage drinking. Any such effects of enhanced enforcement on underage drinking appear to be more directly attributable to an increase in perceived likelihood of enforcement and the resultant perceived inconveniences and/or sanctions to potential drinkers, than to a reduction in access to alcohol per se.     

Evaluating Environmental Change Strategies: Challenges and Solutions

In this introductory article we define environmental change strategies (ECS), summarize the primary challenges associated with evaluating ECS, and provide an overview of the methods researchers have employed to begin to address these challenges. This special issue provides a range of examples, from researchers and practitioners in the field, of different approaches for addressing these challenges. These articles present new methods to understand and test how ECS are implemented and propose methods to evaluate their implementation. The content of the articles covers multiple public health issues, including substance abuse prevention, tobacco control, HIV prevention, and obesity prevention. This special issue is intended to build the evidence base for effective ECS, generate compelling discussion, critical analyses, and spur future research that will help improve the implementation and evaluation of ECS.     

Integrating Human and Natural Systems in Community Psychology: An Ecological Model of Stewardship Behavior

Community psychology (CP) research on the natural environment lacks a theoretical framework for analyzing the complex relationship between human systems and the natural world. We introduce other academic fields concerned with the interactions between humans and the natural environment, including environmental sociology and coupled human and natural systems. To demonstrate how the natural environment can be included within CP’s ecological framework, we propose an ecological model of urban forest stewardship action. Although ecological models of behavior in CP have previously modeled health behaviors, we argue that these frameworks are also applicable to actions that positively influence the natural environment. We chose the environmental action of urban forest stewardship because cities across the United States are planting millions of trees and increased citizen participation in urban tree planting and stewardship will be needed to sustain the benefits provided by urban trees. We used the framework of an ecological model of behavior to illustrate multiple levels of factors that may promote or hinder involvement in urban forest stewardship actions. The implications of our model for the development of multi-level ecological interventions to foster stewardship actions are discussed, as well as directions for future research to further test and refine the model.     

The Performance of Environmental Science in Research Teams

Scientists' practices rely not only on the discursive production of science but also on routine interactions whereby scientists manage their teams and their publics. The metaphor of the theatre helps explain how researchers perform impressions to different audiences. This metaphor can also help analyse how scientists and researchers cooperate in performance teams in order to manage credibility impressions. How are research teams constructed and maintained? How do team members respond to the challenges of coordinating the team and elaborating a common vision given their differences in aims and understandings? From 2005 to 2007 a scientific team worked together in the city of Tuzla, Bosnia and Herzegovina, to develop land remediation measures for coal waste disposal sites. The team was organised around a common front developed through ongoing negotiation and bargaining. Scientists employed different strategies to maintain the team through the development of the project, such as reciprocity, unanimity and bargaining. To accommodate individual views, the common front emphasised the presentation of results and the process of research over its specific content and impact.