ABSTRACT
Introduction 134
Coffee and Caffeine Consumption 134
Coffee Consumption 134
Caffeine Consumption 134
Addiction and Drug Dependence 135
Caffeine Withdrawal 136
Caffeine Withdrawal in Animals 136
Characterization of Withdrawal Symptoms in Humans 136
Tolerance to the Effects of Caffeine 137
Tolerance to Caffeine in Animals 137
Tolerance to Caffeine in Humans 137
Reinforcement Properties of Caffeine 138
Reinforcing Effects of Caffeine in Animals 138
Reinforcing Effects of Caffeine in Humans 139
Is Caffeine Activating the Brain Circuits Underlying Dependence to Drugs? 139
Conclusion 140
References 149
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INTRODUCTION
Caffeine is the most widely used psychoactive substance in the world. Most of the caffeine consumed comes from dietary sources such as coffee, tea, cola drinks, and chocolate. The most notable behavioral effects of caffeine occur after low to moderate doses (50 to 300 mg) and include increased alertness, energy, and ability to concentrate. Moderate caffeine consumption leads very rarely to health risks (Curatolo and Robertson, 1983; Benowitz, 1990; Fredholm et al., 1999; Nawrot et al., 2003). Higher doses of caffeine, however, induce negative effects such as anxiety, restlessness, insomnia, and tachycardia, primarily in a small portion of caffeinesensitive individuals. Four attitudes are positively linked to the quantity of coffee consumed (SECED, 1980). They are, in decreasing order of importance: (1) the need for a stimulant, (2) the preference for strong coffee, (3) the knowledge of coffee, and (4) the preference for the coffee roasting shop. On the other hand, caffeine has also been considered as a potential drug of abuse (Gilliland and Bullock, 1984; Holtzman, 1990), and the possibility that caffeine withdrawal-but not abuse and dependence-should be added to diagnostic manuals has been considered in the U.S. (Hughes et al., 1992). Two recent reviews have detailed the various aspects linked to caffeine dependence (Fredholm et al., 1999; Nehlig, 1999). In this chapter, we will consider whether or not caffeine can be considered a drug of dependence. dependence.
