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better understood as part of the learning process, the consequences of drug use which in turn shape future use. Withdrawal can usefully be seen in the same way, and Carroll and her colleagues report that requiring tolerance and withdrawal as symptoms of dependence in a cohort of 521 subjects recruited from clinical and community sources had little effect on rates of dependence. Eighty-five per cent of subjects who met the criteria for a dependence diagnosis also reported tolerance to that drug. Cocaine and marijuana were the exceptions.
The authors of this study then subjected their data to further analysis in order to examine the concurrent validity of these criteria with severity of substance abuse, family history and psycho-social functioning. They found that, while tolerance and withdrawal items tend to cluster at higher levels of severity, they
“do not emerge as pre-eminent indicators of severity relative to the other criteria” (Carroll et al. 1994 p.19)
It is perhaps worth noting that the phenomenon of clustering of items on tolerance and withdrawal at the severe end of dependence may be the result of the choice of the questions asked. There is a whole range of severity to choose from and the likelihood is that items associated with high levels may have been selected in the first place.
While the field remains divided on the question of the inclusion or not of tolerance and withdrawal in the criteria for dependence, the above study is one of the few empirical evaluations of their role relative to non-physical criteria. Previously, their inclusion has been taken for granted both in definitions of dependence and in scale construction, resulting in controversy over the way in which definitions are derived (Chick 1980b).
In the present study it is hypothesised that there is a unidimensional phenomenon of substance dependence which crosses substance boundaries and is measurable using the Leeds Dependence Questionnaire. This questionnaire does not include items on tolerance and withdrawal per se, but on behaviour that results from their presence as well as behaviour which is reinforced by the drug effect itself.
1.6.1 Implications of the psychological formulation of substance dependence
As a development of the dependence syndrome idea, the major implication of the psychological formulation of dependence is that, as a learned behaviour, dependence is at least
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