DDC and attention deficit-hyperactivity disorder: Genome-wide association studies (GWASs) suggest that cognitive disorders might also result from the cumulative effect of gene variant regulation and parent-of-origin effect,84 which in ADHD has been associated with genes such as DDC, MAOA, PDLIM1, and TTR. We also identified chromatin openness differences related to genes identified in the paracetamol exposed cells.