Addictions

The addictions are chronic relapsing brain diseases, 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 receptor agonists (e.g. heroin and abused prescription opioids) have some common direct or downstream effects, including modulation of  dopaminergic  systems which underlie aspects of mood and reward. Specific addictions also have unique trajectory, morbidity, and pharmacotherapeutic approaches, based on direct and delayed neurobiological adaptations for each drug. Several neurobiological systems have been implicated in addictions, notably opioid receptor and opioid  neuropeptide  gene systems; stress-responsive systems including corticotropin-releasing hormone,  vasopressin , and  orexin ; and  glutamate  and γ-aminobutyric acid systems. The 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.