Coffee and caffeine dependence: What do we know now?

Caffeine is the most widely used psychoactive substance in the world, Although it is usually consumed in rather modest amounts that induce mostly positive effects, caffeine has been considered incidentely as a drug of abuse or even a model of drug abuse. Therefore, the possibility that caffeine abuse, dependence and withdrawal should be added to diagnostic manuals has been considered in the United States. The present paper reviews the available data on caffeine dependence, reinforcement and withdrawal to try to assess in which respect caffeine differs from the classical drugs of abuse. After caffeine cessation, withdrawal symptoms develop in a large portion of the population but they are moderate and last only for a few days. Tolerance to the effects of caffeine on the central nervous system is very limited. Caffeine shows reinforcing properties but only at low doses while high doses induce dysphoric effects and are usually avoided. Conversely to the classical drugs of abuse which lead to quite specific increases in cerebral functional activity and dopamine release in the shell of the nucleus accumbens, the key structure for reward, motivation and addiction, caffeine does not primarily act at the level of that structure and increases glucose utilization in the shell of the nucleus accumbens only at rather high doses that stimulate most brain structures and are already somewhat aversive. In conclusion, although caffeine does share some features of dependence with classical drugs of abuse, they are not sufficient to consider that there is a strong dependence to caffeine in the general population.