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significantly correlated with treatment outcome:
“Clients who presented with higher levels of impaired control on the ICS were less likely to have a successful outcome to treatment.” (Heather et al. 1998 p. 769)
The authors report that degree of impaired control predicted outcome in clients who had returned to drinking at some point during the follow up period and among those aiming for an abstinence goal; it did not predict outcome amongst those aiming for a controlled drinking goal. Further on the question of prediction, when results of the 1998 study were subjected to logistic regression analysis and impaired control was compared with alcohol dependence as a predictor of outcome, it was found that impaired control was not an independent predictor for the whole sample, but only for those who had wished to stop drinking and had returned to drinking during the follow up period. For this sub-sample, impaired control was an independent predictor of outcome when the effects of dependence were removed. Although impaired control was not able to predict choice of drinking goal, the authors nonetheless argue that it merits separate measurement because of its ability to predict relapse in clients who have chosen a goal of total abstinence.
Current theory of dependence places impaired control at the very heart of the phenomenon and empirical attempts to resolve the question of whether impaired control is part of dependence or closely related to it appear to be leaning towards the former position (Heather et al. 1998; Stockwell et al. 1994; Raistrick et al. 1994) though Heather et al. (1998) have made a claim to continue to measure it separately for the potential clinical utility of doing so, with particular reference to prediction of relapse amongst clients who are aiming for an abstinence goal. In the present study, where the nature of decline in dependence is under investigation, a measure of dependence or of a component of dependence was required in addition to the main measure of dependence used (the Leeds Dependence Questionnaire). The Impaired Control Scale was chosen as the theoretical deliberations which informed its development, coupled with its performance in the two studies described above rendered it most suitable for this purpose. As the scale was developed and validated in populations of problem drinkers, its use in the present study required a version suitable for heroin users as well as for alcohol users. I decided to use the original scale with the problem drinker group in the main study (Study 4) and to use a version adapted for heroin users and as close as possible to the original scale, with the heroin user group. Adaptation and validation of the original ICS for this purpose is reported below.
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