Epigenetics of attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder. Besides genetic factors, several environmental factors occurring either before the emergence of the disorder (prenatally or perinatally), or when the disorder is already diagnosed, or close to its emergence, such as childhood maltreatment have been shown to play a major role in ADHD. Epigenetics has attempted to link these environmental factors to the disorder and its persistence in adulthood. Findings of epigenetic studies have implicated genes encoding: proteins involved in neurotransmission, namely dopamine receptor4 (. DRD4), serotonin transporter (. SLC6A4), serotonin receptor 3A (. 5-HT3AR); proteins involved in the epigenetic machinery like histone deacetylase1 (. HDAC1) and methyl-CpG binding protein2 (. MeCP2); and proteins involved in brain development, namely vasoactive intestinal peptide receptor 2 (. VIPR2). Nevertheless the number of studies is limited and replications as well as new studies are still needed to better define the underlying neurobiological mechanisms of ADHD.