Addictions

The substance use disorders are chronic relapsing brain diseases associated with drug use, often referred to as addictions, with behavioral manifestations and considerable morbidity. Addictions are complex disorders with genetic, epigenetic, neurobiological, and drug exposure factors, as well as environmental factors. Addictions to specific drugs such as alcohol, nicotine/tobacco, cocaine/psychostimulants (e.g., methamphetamine), and μ-opioid peptide receptor agonists such as heroin, abused prescription opioids, and fentanyl analogs have some common direct or downstream effects, including modulation of dopaminergic systems, which underlie aspects of mood and reward. Specific addictions also have unique trajectories, morbidities, and pharmacotherapeutic approaches based on direct and delayed neurobiological adaptations for each drug. Several neurobiological systems have been implicated with the addictions, notably opioid receptor and opioid neuropeptide gene systems, stress-responsive systems including corticotropin-releasing hormone (CRH), vasopressin and orexin, as well as glutamate and γ-aminobutyric acid systems. Cumulatively, public health costs of the addictions are massive; there remains a great need for translational neurobiological understanding of these diseases, potentially leading to better treatments, including advances in personalized medicine.