In sum, the present data showed that ADHD symptomatology improved in individuals whose higher-order working memory manipulation skills got better over time if they inherited two copies of the common allele of DRD1 SNPs rs4532 and rs265978. These SNPs tag SNP rs686, a DRD1 variant that changes D1 receptor expression by >25% (Huang et al., 2008). Conversely, carrying the minor allele decoupled the link between ADHD symptoms and working memory manipulation. Such work may help identify subgroups of children with ADHD who will preferentially respond to certain remediation strategies such as working memory training to alter long-term outcome. These findings also shed new light on DRD1 as a modifier gene that influences the trajectory of ADHD but not necessarily the onset of symptoms in childhood.
