Drug Addiction also known as drug dependence is a pathological disorder marked by compulsive use of a drug or drugs. A person suffering with drug addiction will always be psychologically dependent on a chemical (illicit or licit) and often including physical dependency to a chemical (illicit or licit).

The most common substances that fall under the category of drug addiction are opiate addiction (heroin addiction, methadone addiction, oxycontin addiction, norco addiction, vicodin addiction), benzodiazepine addiction (xanax addiction, valium addiction, ativan addiction, klonipin addiction), cocaine addiction (crack addiction, powdered cocaine addiction, liquid cocaine addiction), amphetamine addiction (methamphetamine addiction, adderall addiction, Ritalin addiction). Though marijuana addiction, ecstasy addiction, PCP addiction and Special K addiction are also very common.