ADHD: A Critical Review of Dopamine Genes and Cortical Thickness as Etiological Mechanisms

Literature on the role of the dopaminergic system in attention-deficit/hyperactivity disorder (ADHD) is rich, and more recent studies supporting dopaminergic genetic mechanisms as the basis for ADHD symptomatology continue to make headway. Likewise, the relationship between cortical thickness (CT) and ADHD is well-researched, though exact mechanisms remain unclear. Although the exact etiology remains unclear, the vast field of ADHD research indicates that the disorder's complex etiology and pathophysiology are the likely product of interactions between genetic and environmental factors, resulting in increased susceptibility and neurostructural differences. The relationships between dopamine (DA) and CT and their underpinning genetic mechanisms, i.e., relevant polymorphisms and developmentally driven aspects of gene expression, beg for further exploration. However, the nature of this association remains somewhat undefined as the research is plagued by limitations related to genetic, structural, and functional imaging techniques, inconsistent subtype categorization, and a need for more ethnically- and age-diverse participants. This critical review analyzes the current state of the literature and calls for more research that explores linkages between dopamine genes, CT, and ADHD, with particular consideration of the impact of neurodevelopment across the lifespan.