Brain science is at the core of future understanding of how drugs affect behavior and their consequent impact the society. Extraordinary advances in the past three decades have meant that now much is understood about the connectivity of the brain and how its functionality depends on chemical messages passing among nerve cells, or neurons, in the form of neurotransmitters they release that bind to receptors. Psychoactive substances exert their effects by affecting the regulation of neurotransmitters or simulating their actions at their receptors, and subsequently within the nerve cell itself, often in highly specific ways. It is now understood that many drugs work in molecular terms and they may work, at least initially, in the brain. Moreover, one now knows in broad terms how different parts of the brain work at a systems level to produce behavioral and cognitive output. A complementary advance is the application of some aspects of neural decision making theory to the explanation of the behavior of individual substance abusers. Vulnerability or susceptibility to some actions of psychoactive substances, including both cognitive enhancement and dependence, depends on individual differences based on genetic or environmental, including developmental factors. Although in the society drug abuse is viewed as a social or moral problem best handled through the criminal justice system, the growing scientific evidence suggests instead that addiction is a chronic, relapsing, and treatable brain disorder that can result from prolonged effects of drugs on the brain.
Department of Neuroscience

Robbins, T. (Trevor), Cardinal, R.N. (Rudolf N.), DiCiano, P. (Patricia), Halligan, P.W. (Peter W.), Hellemans, K, Lee, J. (Jonathan), & Everitt, B.J. (Barry J.). (2007). Neuroscience of Drugs and Addiction. In Drugs and the Future (pp. 11–87). doi:10.1016/B978-012370624-9/50006-2