Drug addiction is a condition characterized by compulsive drug intake, craving and seeking, despite negative consequences associated with drug use.
Although being addicted implies drug dependence, it is possible to be dependent on a drug without being addicted. People that take drugs to treat diseases and disorders, which interfere with their ability to function, may experience improvement of their condition.
Such persons are dependent on the drug, but are not addicted. One is addicted, rather than merely dependent, if one exhibits compulsive behavior towards the drug and has difficulty quitting it.
To qualify as being dependent a person must
Substance abuse can occur with or without dependency, and with or without addiction. Substance abuse is any use of a substance, which causes more harm than good.