A definition of substance dependence that is frequently cited is from DSM-IV-TR, the fourth edition text revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM) issued by the American Psychiatric Association. The DSM-IV TR says "the essential feature of substance dependence is a cluster of cognitive, behavioral, and psychological symptoms indicating that the individual continues to use the substance despite significant substance-related problems" (DSM-IV-TR, p. 192). The individual has developed tolerance to the drug and will exhibit some or all symptoms if the drug is discontinued abruptly. However this does not apply to certain classes of drugs such as hallucinogens. With substance dependence, there is a compulsion to continue using the drug despite negative consequences in one's life. There may even be a timeframe during which the individual does not use the drug at all (oftentimes to prove to himself or someone else that he is not "addicted" to the drug). But when the individual resumes use of the drug, the same pattern continues and the mere fact that he/she started using the drug again after so many negative consequences in life as a primary indicator of "addiction" to that drug. So another way of saying it is: a pathologic relationship with any potentially addictive mood altering substance that results in negative consequences in one's life, yet the individual cannot permanently abstain from substance or addiictive behavior. The DSM-IV TR provides this succinct set of criteria for substance dependence: "Maladaptive substance use, leading to clinically significant impairment or distress, as manifested by three (or more) of the following, occurring at any time in the same 12 month period:

(1) tolerance, as defined by either of the following: a. a need for markedly increased amounts of the substance to achieve intoxication or desired effect b. markedly diminished effect with continued use of the same amount of the substance

(2) withdrawal, as manifested by either of the following: a. the characteristic withdrawal syndrome for the substance b. the same (or a closely related) substance is taken to relieve or avoid withdrawal symptoms

3) the substance is often taken in larger amounts over a longer period than was intended

(4) there is a persistent desire or unsuccessful efforts to cut down or control substance use

(5) a great deal of time is spent in activities necessary to obtain the substance (e.g., visiting multiple doctors or driving long distances), use the substance (e.g., chain-smoking), or recover from its effects

(6) important social, occupational, or recreational activities are given up or reduced because of substance use

(7) the substance use continues despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the substance (e.g., current cocaine use despite recognition of cocaine-induced depression, or continued drinking despite recognition that an ulcer was made worse by alcohol consumption)" (DSM-IV-TR, p. 197). DSM-IV TR provides specific criteria for the following substances: amphetamine caffeine cannabis cocaine hallucinogens inhalants nicotine opioids phencyclidine sedatives, hypnotics, anxiolytics, and polysubstance dependence.

http://psychcentral.com/disorders/sx16.htm

http://www.answers.com/topic/substance-abuse-and-dependence-causes-and-symptoms

http://www.behavenet.com/capsules/disorders/subdep.htm