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quality to the effects of the drug. These are some of a number of operant explanations of drug dependence which support the observation that the pursuit of the effect and the maintenance of the effect of the drug may be as important, if not more important in driving the drug seeking and drug using behaviour as is the avoidance of the negative consequences of not using or stopping using (the experience of withdrawal symptoms).
Raistrick et al. (1994) developed their understanding of substance dependence on the basis of in-depth interviews conducted with patients who were asked for their descriptions of dependence phenomena. As a result of this, they incorporated into their formulation of substance dependence the pursuit of the effect, the maximisation of the effect and the maintenance of a constant state as being of equal importance as the avoidance of withdrawal symptoms.
Increasingly investigators of dependence have shown that pursuit of the effect - the positive reinforcement potential of the behaviour, or positive incentive motivation - is as important, if not more important than drive reduction, the negative reinforcement potential of the behaviour. Jaffe (1989) argues that, contrary to the traditional view that dependence is primarily driven by the need to avoid or attenuate withdrawal symptoms, the pursuit of the drug effect is more strongly associated with drug seeking behaviour than is the fear or avoidance of withdrawal. To support this point he cites the distinction between those hypnotic or sedative drugs which produce neuroadaptation and a withdrawal syndrome on cessation of use, but are not associated with self administration. Characteristics of such drugs are that they are long acting and are not intensely euphorigenic. Similarly with the benzodiazepines, he demonstrates that, while all of these drugs are capable of inducing neuroadaptation and a withdrawal syndrome, the only ones that are of concern as drugs of abuse are those which are rapidly absorbed, in other words that have a rapidly positively reinforcing effect. Equally he shows that the phenomenon of craving, defined as a strong urge to repeat the use of a drug (though no universally accepted definition of the term exists) is reported by patients and observed in animals where no evidence of neuroadaptation and a physical withdrawal syndrome exists. Contrary to the traditional view that craving is linked to the phenomenon of tolerance and withdrawal exclusively, there is increasing evidence that it can equally occur as a result of the memory of positive reinforcement and that this memory of positive reinforcement accounts for the observation that craving persists long after the end of the withdrawal syndrome or indeed where no withdrawal syndrome has developed. Craving may be better understood as a response to previously conditioned cues which may be physical, psychological or social in nature (Rankin et al. 1979).
Positive reinforcement plays an important role in the maintenance of dependence through
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