The use and abuse of various psychoactive chemicals has been a fact of life almost since humans first walked the planet. Beer making, for example, began soon after the Mesopotamians domesticated barley to make bread approximately 8000 bc, whereas alcohol per se dates to at least Paleolithic times when humans fermented fruit juice, grain, and honey. The process of distillation dates from ad 800 Arabia. Descriptions of intoxication and drunkenness filled ancient writings, as did pleas for moderation. The Old Testament, for example, condemned excess but did not condemn the use of alcohol. Stimulant use likewise has a long history. For example, Chinese physicians have been using Ma-huang, which contains ephedrine, for more than 5000 years. The inhalation of volatile substances to produce euphoria can be traced to the ancient Greeks, and various psychoactive plants have been used throughout the world as an important part of religious, medicinal, and cultural activities for various ethnic and cultural groups for centuries. Given this lengthy and ubiquitous history, it is clear that some individuals in some cultures are not able to limit their use of psychoactive substances to the prevailing norms within the individual's larger culture, although the individual's aberrant use pattern may be sanctioned by the individual's subculture.

Psychoactive substances are used primarily to gain access to pleasant events or escape or avoid unpleasant events. These events can be internal (thoughts, feelings, images) or external (environmental events, exchanges with others) to the user. These strategies are powerfully reinforced by the immediate consequences determined by the pharmacologic properties of the chemical and the route of administration (e.g., oral, smoking, injecting, and so forth). As we shall see later, genetics and learning may also play a role in the reinforcing properties of psychoactive substances.<sup>2 Anthenelli M., Schuckit M. Genetics Substance Abuse: A Comprehensive Textbook Baltimore: Williams & Wilkins (1997). 

Cliquez ici pour aller à la section Références</sup> The long-term disastrous consequences are days or even years in the future and, thus, do not exert as much control over the individual's substance using or nonusing behavior as immediate consequences do, especially when the individual is attempting to escape or avoid an immediate aversive or unpleasant event. For complex and not entirely understood reasons, some individuals repeatedly use substances in a manner that is either risky or harmful to self or others. It is these patterns of use that have been termed substance use disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM)–IV.<sup>1 American Psychiatric Association   Diagnostic and Statistical Manual of Mental Disorders Washington, DC: American Psychiatric Association (1994). 

Cliquez ici pour aller à la section Références</sup> We discuss some of the factors that are associated with such use and some of the complexities involved in detection, especially when the use is subtle and is obscured by problems of making a differential diagnosis from other psychiatric and medical conditions. Substance-induced disorders must, of course, also be part of the discussion as well, because by definition their occurrence means there is a substance use problem that must be detected and addressed. Therefore, implied in our discussion is the use of DSM-IV<sup>1 American Psychiatric Association   Diagnostic and Statistical Manual of Mental Disorders Washington, DC: American Psychiatric Association (1994). 

Cliquez ici pour aller à la section Références</sup> categories of substance abuse, substance dependence, substance-induced disorders, and the International Classification of Disease–10<sup>37 World Health Organization   Tenth Revision of the International Classification of Disease (ICD-10) Geneva: World Health Organization (1992). 

Cliquez ici pour aller à la section Références</sup> category of harmful use. A brief review of the DSM-IV diagnostic criteria for abuse and dependence is helpful prior to our discussion of risk factors and the more subtle diagnostic problems. The criteria are presented in Table 1 and Table 2. Note that with abuse, problematic consequences occur or the use is hazardous. With dependence, problems may be occurring as the result of the use, but in addition there may be physiologic signs of addiction (in applicable substances); loss of control; overvaluing the substance; and centering one's life around obtaining, using, and recovering from the substance's effects.