Definitions
Slightly more than half of Americans aged 12 or older reported being current drinkers of alcohol in the 2008 survey (51.6 percent). This translates to an estimated 129.0 million people, which is similar to the 2007 estimate of 126.8 million people (51.1 percent).6
Substance use disorder - involves the dependence on, or abuse of, alcohol and/or drugs, including the nonmedical use of prescription drugs.7
Addiction - a chronic, neurobiologic, relapsing disease characterized by compulsive drug-seeking and abuse and by long-lasting chemical changes in the brain.8 It has genetic, psychosocial and environmental factors influencing its development and manisfestations. It is characterized by behaviors which include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving.9
Physical Dependence - state of adaptation which is manifested by a drug class specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist.9
Tolerance - state of adaptation in which exposure to a drug induces changes that result in a decrease of one or more of the drug's effects over time.9
Links:
NIDA for Teens - the Science Behind Drug Addiction
National Institute on Drug Abuse
Substance Abuse and Mental Health Administration