Addiction is a dependence, on a behavior or substance, that a person is powerless to stop. The term has been partially replaced by the word dependence for substance abuse. Addiction has been extended, however, to include mood-altering behaviors or activities. Some researchers speak of two types of addictions: substance addictions such as alcoholism, drug abuse, and smoking; and process addictions such as gambling, spending, shopping, eating, and sexual activity. Many addicts are addicted to more than one substance or process.

Addiction is one of the most costly public health problems in the United States. It is a progressive syndrome, which means that it becomes a more severe problem over time unless it is treated.

Addiction to substances results from several factors. Some substances are more addictive than others, either because they produce a rapid and intense change in mood; or because they produce painful withdrawal symptoms when stopped...