Toward an account of individual differences in drug abuse.

What is drug addiction? It is drug taking on the part of the individual that is usually excessive, harmful to the individual or his/her social environment, and which therefore presents a significant public health problem. The chapters in this technical review deal with the variety of issues of why drug addiction affects only some of us. As documented in these chapters, many of us are exposed one or more times to drugs with abuse potential, yet only a few of us go on to demonstrate drug addiction. Why is this the case? Some believe, as I do, this to be a central, vexing question—addressed often, but not yet satisfactorily answered.