ever, the committee has adopted several semantic conventions to promote clarity and avoid redundancy. First, the term drug, unmodified, refers to all psychoactive drugs, including alcohol and nicotine. When reference is intended to refer solely to illicit drugs such as heroin, cocaine, and other drugs regulated by the Controlled Substances Act, the committee says so explicitly. Occasionally, to ensure that the intended meaning is clear, the report refers to "illicit drugs and nicotine" or to "illicit drugs and alcohol," as the case may be.

The report employs the standard three-stage conceptualization of drug-taking behavior that applies to all psychoactive drugs, whether licit or illicit. Each stage—use, abuse, dependence—is marked by higher levels of use and increasingly serious consequences. Thus, when the report refers to the "use" of drugs, the term is usually employed in a narrow sense to distinguish it from intensified patterns of use. Conversely, the term "abuse" is used to refer to any harmful use, irrespective of whether the behavior constitutes a "disorder" in the DSM-IV diagnostic nomenclature. When the intent is to emphasize the clinical categories of abuse and dependence, that is made clear.

The committee also draws a clear distinction between patterns of drug-taking behavior, however described, and the harmful consequences of that behavior for the individual and for society. These consequences include the direct, acute effects of drug taking such as a drug-induced toxic psychosis or impaired driving, the effects of repeated drug taking on the user's health and social functioning, and the effects of drug-seeking behavior on the individual and society. It bears emphasizing that adverse consequences can be associated with patterns of drug use that do not amount to abuse or dependence in a clinical sense.

Behavioral research has contributed to our understanding of many of the factors involved in drug abuse, including initiation, maintenance, cessation, and relapse. The major contribution of behavioral research to the study of drug abuse has been the development of the drug self-administration model, which has been augmented by the development of additional complementary models. Behavioral models are useful for developing drug abuse pharmacotherapies; improving treatment engagement and compliance; developing novel procedures for both strengthening weak positive behaviors and attenuating strong drug-related behaviors; addressing questions related to mechanisms of craving and relapse; and promoting better understanding of drug use over the life span of drug users. Increased understanding of various drugs' mechanisms of action can also lead to better understanding of behavior and of vulnerability to