Dependence can be understood as a form of conditioning where two factors are associated due to their co occurrence in time and space. Thus dependence on a particular drug can be established with the presence of association, as a result of co occurrence, between the induce of any drug followed by a certain physiological or psychological state, and if the resulting state is pleasure the act is reinforced. For example, the act of alcohol intake is reinforced by the fact that it leads to altered state of consciousness during stress and weak recollection of the emotional distress at the time of recovery.

To clarify the concept of addiction it is important to know how it is different form ordinary usage of any drug. Although a number of drug addicts claim that they take a certain drug by choice and can quit whenever they like, however it is often untrue and most drug users realize it when they have already become abusers.

The Diagnostic and Statistical Manual of Mental Disorders fourth edition Text Revision (DSM IV- TR) provides a subsection of Substance Related Disorders which serves as a comprehensive guide for the understanding of addiction. The Diagnostic and Statistical Manual of Mental Disorders uses an individual's level or quality of psychosocial functioning; that is the ability to carry out every day life tasks, and maintain a level of social, occupational, and educational adjustment, as a yard stick to the determine the existence of any abnormality. Thus any kind of drug usage can be termed as abuse or addiction if it begins to form adverse effects on an individual's psychosocial functioning.