Acording the "WHO lexicon of alcohol and drug terms" habituation means, "becoming accustomed to any behaviour or condition, including psychoactive substance use. In 1957 a WHO Expert Committee distinguished drug habituation from drug addiction on the basis of the absence of physical dependence, desire rather than compulsion to take the drug, and little or no tendency to increase the dose" In 1964 both terms " addiction" and "habituation" were replaced with the term "drug dependence" Four aspects characterize the habit formation: