Summary

The concept of the "dependence syndrome", as proposed by Edwards and Gross, originally hypothesised only for alcoholism, was broadened to apply to other psychoactive substances following changes in expert opinion regarding the nature of dependence. The drug dependence syndrome reduced the traditional emphasis on tolerance and withdrawal, and attached greater importance to symptoms of a compulsion to use, a narrowing of the drug-using repertoire, rapid reinstatement of dependence after abstinence, and the high salience of drug use in the user's life.

While current psychiatric taxonomies recognise amphetamine dependence, its existence is quite contentious, and little research has examined the applicability of the dependence notions to this drug. Of the limited research available pertaining to this issue, the most informative has concentrated on amphetamine withdrawal and withdrawal relief drug-taking as hallmarks of amphetamine dependence. These notions fit well with a drug that produces a clearly defined, physiologically based withdrawal syndrome, such as the opiates, but it was feared such symptoms may be less relevant to a drug such as amphetamine, for which the withdrawal syndrome is somewhat more nebulous. In such cases, it is reasonable to hypothesise that the positively reinforcing aspects of the drug, as well as its negative reinforcement capacity, are both important factors in dependence.

In the present study, 132 regular amphetamine users, dependent by DSM-111-R criteria, were administered a structured interview schedule in order to determine, firstly, whether there is an amphetamine dependence syndrome, and secondly, to begin explicating what the dimensions underlying such a syndrome might be, and in particular, the relative contributions of appetitive and aversive motivation in heavy amphetamine use.

A number of different questionnaires were administered and different analyses performed. However, a consistent picture emerged: clear evidence for a continuum of dependence was obtained, with many theoretically relevant differences between those individuals diagnosed as severely and mild/moderately dependent by DSM-111-R criteria; and more dependent users were distinguished from their less dependent counterparts by items which assessed the negative reinforcement capacity of amphetamine. That is, as the use pattern moves from recreational to heavy, the euphoric, energizing, confidence building effects of the drug remain important in motivating use. However, in heavy, more dependent users, other motivations, involving the drug's capacity to remove some aversive physical or emotional state, are also important. These results have implications for the current debate on the status of amphetamine dependence, as well as for stimulating research into appropriate interventions for amphetamine dependence treatment.