The term addiction is somewhat of an umbrella term referring to any kind of compulsive use or excessive dependence on a substance or activity. In the DSM-IV, substance abuse is characterized by excessive use which continues despite significant negative consequences. More specifically, substance abuse requires recurrent use of the substance, resulting in failure to meet major role obligations; exposure to situations that are physically hazardous (e.g., drunk driving); recurrent legal problems; and continued use despite repeated negative social consequences.

Substance dependence is a more severe disorder. In addition to causing social, occupational, and/or financial problems, substance dependence also requires a physiological addiction to the drug. The two most important features involve tolerance and withdrawal. Additionally, there can be an increase in the amount of substance used over time, a persistent desire to cut down, or unsuccessful efforts to do so, considerable amounts of time spent in pursuit of the substance, sacrifice of important life activities because of substance use, and/or the continued use of the substance despite clear physiological or psychological damage from it.