Drug abuse is usually viewedas a behavior that occurs because of what the drugs do in the body. Most people assume that drug abuse is mainly driven by the immediate, attractive effects and sensations produced by the drugs—their physiological and psychological effects. But there is another, less direct way drugs can become of overwhelming importance to a person and dominate life. Excessive drug use can develop as a side effect of other strongly desired behavior that, for various reasons, cannot be engaged in or completed.

For example, for any one of a number of reasons a person may not be able to do something they are motivated to do: They may not be permitted to do it, the goals of the behavior may not be available to them, or the person may not have the skills or knowledge required to perform the behavior...