Epigenetics refers to heritable and de novo changes in gene expression that do not involve changes in DNA sequence102. Thus, individuals with the same genotype may demonstrate variations in gene expression in response to exogenous (e.g. prolonged exposure to stress) or endogenous (e.g. elevated cortisol levels in response to stress) environments. Such modification often occurs early in development103 and mechanisms inducing epigenetic modification include gene methylation, chromatin remodeling and imprinting. Does epigenetic modification contribute to the etiology of adolescent SUDs and if so, is it a cause or consequence of SUDs? A host of epidemiological studies have shown the important role of childhood traumas, parental neglect and other early adversity on elevated risk for adolescent SUDs – to what extent these environmental risk factors induce change in expression of addiction-related genes is unknown. Furthermore, such epigenetic mechanisms may be one of several pathways from drug experimentation to persistent use and dependence. What is better understood is drug-induced neuronal plasticity - for instance, repeated cocaine administration has been found to relate to modification of neuronal plasticity and increased preference for cocaine
