CHEMICAL DEPENDENCY IS a physical or psychological need for a chemical that is taken for nonmedical reasons and produces a noticeable effect on the body. The need is referred to as a "dependency" because once a person stops using the chemical, physical, emotional, or psychological withdrawal symptoms occur. There are a number of different chemicals, such as alcohol, tobacco, and drugs, that people become dependent upon, all of which may have a harmful effect on the user.

A progressive need

Chemical dependency is a progressive condition. That is, it begins slowly and grows until it dominates a person's life. As chemical dependency progresses, users have a hard time limiting their use of the chemical. They may feel that they cannot experience pleasure or relief from stress without the chemical and thus may develop a psychological or physical need for it...