ABSTRACT
In recent years, there has been increasing awareness of the role of environmental factors in neurodevelopmental disorders, including attention deficit/hyperactivity disorder (ADHD) (e.g., Banerjee et al. 2007; Nigg 2006b; Swanson et al. 2007). In this review we provide a focused overview of ADHD for researchers who are interested in the association between environmental exposures and ADHD risk but have little familiarity with the disorder’s diagnosis and prevalence, the functional domains that are impaired, or the underlying changes in brain structure and function. A second goal is to summarize behavioral deficits that are hallmarks of ADHD in order to facilitate comparisons with behavioral deficits associated with widely dispersed environmental chemicals-specifically lead and polychlorinated biphenyls (PCBs), which are reviewed in the companion paper by Eubig et al. (2010). At present, there is compelling evidence suggest-
ing that several key brain functions are implicated in ADHD-attention, executive functions, processing of temporal information, and responses to reinforcement (Nigg and Nikolas 2008)—all of which are critical for modulating behavior (Barkley 1997; Nigg and Casey 2005). We review several meta-analyses published since 2004 that compare the performance of children and adolescents diagnosed with ADHD against non-ADHD controls on neuropsychological tasks measuring attention and executive functions. Additionally, we summarize the performance of ADHD children and adolescents on tests of temporal information processing and responses to reinforcement, which have not been evaluated in meta-analyses to date.
