Caffeine Reinforcement, Discrimination, Tolerance and Physical Dependence in Laboratory Animals and Humans

Abstract

Caffeine is an excellent model compound for understanding drugs of abuse/dependence (HOLTZMAN 1990). Historically, caffeine use dates back hundreds, possibly thousands, of years (GRAHAM 1984). Caffeine use spread worldwide from its initially constrained geographical origins, despite recurring efforts to restrict or eliminate its use motivated on moral, economic, political, religious or medical grounds (AUSTIN 1979). Currently, caffeine use is almost universal, with more than 80% of adults in North America regularly consuming behaviorally active doses of caffeine (GILBERT 1976; GRAHAM 1978; HUGHES et al. 1993b). The broad generality of caffeine self-administration is reflected in the facts that, worldwide, caffeine consumption occurs in markedly different vehicles (e.g., drinking of coffee, tea, maté, soft drinks; chewing of kola nuts; consumption of cocoa and guarana products) and in widely different, but culturally well-integrated, social contexts (e.g., the coffee break in the United States; tea time in the United Kingdom; kola nut chewing in Nigeria). The dependence-producing nature of caffeine is reflected in the experience of most people who know someone who has expressed a “need” for a cup of coffee or who claimed to be “addicted” to coffee or their morning caffeinated beverage of choice. Consistent with this anecdotal experience, a recent random–digit telephone survey found that about 17% of current caffeine users met the DSM-III-Rpsychiatric criteria for being moderately or severely drug dependent on caffeine (HUGHES et al. 1993b).