Behavioral and biological factors associated with individual vulnerability to psychostimulant abuse.

It is common knowledge that enormous individual differences in drug intake exist in humans (de Wit et al. 1986). A large number of people have tried drugs at least once, but for most of them drug use consists in single or few nonrenewed experiences. Among people that persist in taking drugs, drug use can remain an occasional behavior that is limited, for example, to weekends or parties. Finally, only some subjects among drug users develop drug abuse, i.e., a compulsive drug use that becomes the principal goal-directed behavior of the subject (O’Brien et al. 1986). The origin of the peculiar vulnerability to develop drug abuse observed in some individuals is one of the principal questions to be answered about addiction.