Addiction is a brain disorder characterized by compulsive engagement in rewarding stimuli despite adverse consequences.  It is a disorder of the brain’s reward system which arises through transcriptional and epigenetic mechanisms and develops over time from chronically high levels of exposure to an addictive stimulus (food, drug, behavioral and high-thrill cultural activities, etc.).

Examples of drug and behavioral addictions include alcoholism, marijuana addiction, amphetamine addiction, cocaine addiction, nicotine addiction, opioid addiction, food addiction, video game addiction, gambling addiction, and sexual addiction.