Genetics of ADHD

Abstract

Since the 1990s, substantial advances have been made in genetic research on attention-deficit/hyperactivity disorder (ADHD), although a conclusive ADHD gene, or set of genes, has not been identified. Although many researchers believe that such discoveries are not far off, investigators have encountered an obstacle to finding genes responsible for ADHD-namely, the need to refine the phenotypic (i.e., diagnostic) approach used to identify subjects for molecular genetic studies (Hudziak 1997). From twin studies, we have learned that the symptoms of ADHD are highly heritable, with genes accounting for 45%-90% of the total variance in hyperactivity-impulsivity and inattention across the life span (Faraone 2004; Larsson et al. 2006). However, we also have encountered difficulties with rater bias, developmental bias, gender bias (Hudziak et al. 1998b), and limitations of the DSM categorical approach to psychiatric illness. From family studies, we have learned that ADHD is highly familial and associated with several comorbid conditions. Finally, molecular genetic studies have provided us with a window on the relations between specific genes and at least some cases of ADHD. As Pauls (2005) has reported, ADHD is a genetically and phenotypically complex disorder that may result from different combinations of genetic and environmental factors that could lead to similar, if not identical, outcomes. (PsycInfo Database Record (c) 2021 APA, all rights reserved)