form the basis of many current strategies in the design of new drug treatments for neuropsychiatric disorders. Additionally, drug abuse research has contributed to the development of brain imaging techniques.

Drug abuse research has also provided a major impetus for neuropharmacological research in psychiatry since the late 1950s, when it was discovered that LSD (lysergic acid diethylamide; a hallucinogen that produces psychotic symptoms) affected the brain's serotonin systems (Cooper et al., 1991). That seminal discovery stimulated decades of research in the neuropharmacological basis of behavior and psychiatric disorders. The impact on antipsychotic research has been dramatic. In addition, stimulants (e.g., cocaine and amphetamine) were found to produce a state of paranoid psychosis, resembling schizophrenia, in some people. The actions of stimulants on the brain's dopamine pathways continue to inform researchers of the potential role of those pathways in the treatment, and perhaps the pathophysiology, of schizophrenia (Kahn and Davis, 1995). Drug abuse research also has had an impact on antidepressant research (e.g., the actions of drugs of abuse on the brain's serotonin systems have provided useful models with which to investigate the role of those systems in depression and mania). Depression is a risk factor for treatment failure in smoking cessation (Glassman et al., 1993) and depression-like symptoms are dominant during cocaine withdrawal (DiGregorio, 1990). Consequently, treatment of depression in nicotine and cocaine-dependent individuals has been an area of interest for drug abuse research.

Some drugs that are abused, most notably the opioid analgesics, have essential medical uses. Since its founding, NIDA has been the major supporter of research into brain mechanisms of pain and analgesia, analgesic tolerance, and analgesic pharmacology. The resulting discoveries have led to an understanding of which brain circuits are required to generate pain and pain relief (Wall and Melzack, 1994), have revolutionized the treatment of postoperative and cancer pain (Folly and Interesse, 1986; Car et al., 1992; Jacob et al., 1994), and have led to improved treatments for many other conditions that result in chronic pain (see Chapter 3).

VOCABULARY OF DRUG ABUSE

Ordinarily, scientific vocabulary evolves toward greater clarity and precision in response to new empirical discoveries and reconceptualizations. That creative process is evident within each of the disciplines of drug abuse research covered in various chapters of this report. Interestingly, however, the words describing the field as a whole, and connecting each chapter to the next, seem to defy the search for clarity and precision. Does "drug" include alcohol and tobacco? What is "abuse"? Are use and



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