In summary, we have shown that the science of epigenetic biomarkers for substance use disorders is still in its infancy. For smoking, the substance which causes the greatest morbidity and mortality worldwide, several promising loci found using array-based technology have replicated across multiple studies and have potential for clinical translation. For alcohol, fewer studies have been done and epigenetic signatures appear to be more subtle, but there is potential for translation if recent findings are replicated. For other substance use disorders, despite active investigations in the areas of candidate gene studies and animal models, minimal study using array-based technology has been done and there are no loci with immediate potential for clinical translation.
