Substance abuse , as a disorder , refers to the abuse of illegal substances or the abusive use of legal substances.
Alcohol is the most common legal drug of abuse.
Substance dependence is used to describe continued use of drugs or alcohol, even when significant problems related to their use have developed. Signs include an increased tolerance or need for increased amounts of substance to attain the desired effect, withdrawal symptoms with decreased use, unsuccessful efforts to decrease use, increased time spent in activities to obtain substances, withdrawal from social and recreational activities, and continued use of substance even with awareness of physical or psychological problems encountered by extent of substance use. Cultural and societal norms influence acceptable standards of substance use. Public laws determine the legal use of substances. The question of whether there is a normative pattern of substance use in adolescence remains controversial.