International Guidelines for the Estimation of the Avoidable Costs of Substance Abuse

8 Conclusion

This study addresses the provision of guidelines for estimation in an area which represents an almost completely new area of research. We should underestimate neither the importance of such estimation, nor their difficulties, nor the interpretation of the results. In principle, the aim should be a "gold standard" methodology which is solidly grounded in epidemiological and economic theory, and one for which sound data are available. Such gold standard research would yield results which could be applied to maximise the quality of public policies designed to deal with the problem of substance abuse.

In practice, it is never easy to apply a gold standard. This was clearly acknowledged in the development of the original aggregate cost Guidelines and it is certainly the case in the estimation of avoidable costs. In the latter case it is necessary both to develop the necessary theory and to review and improve available data. It is also important to clarify the theoretical distinction between minimum achievable levels of substance abuse and optimal levels of abuse. These guidelines are concerned with the estimation of feasible minimum levels, not optimal levels.

This study reviews three broad possible approaches to the estimation of avoidable costs. The first method involves what might be called a classic epidemiological approach. This is probably the most theoretically correct of the three, being exposure-based, but also is the one which has the most challenging data requirements. A second approach is based on what has become known as the Arcadian normal, which uses best outcomes (in terms of morbidity and/or mortality in comparable countries) as the basis for estimating avoidable proportions. It was, however, agreed at the Ottawa workshop that an exposure-based methodology was superior to one based on outcomes. The desirability of an exposure-based approach applied in a situation of data deficiency led to a third methodology using exposure-based comparators, drawing on international data recently published by the WHO on attributable fractions.

All three methodological approaches addressed here relate to using morbidity and mortality cost calculations to estimate the Feasible Minimum. Studies of the avoidable costs of crime are, in future, likely to reveal further complexities which will require careful analysis and interpretation.

There are also likely to be benefits from the examination of international evidence on the effectiveness of interventions designed to deal with the levels, or adverse effects, of substance abuse. Where strong evidence exists about the effectiveness of particular interventions, comparison of actual policy mixes with interventions known to be effective in other countries may help to indicate the proportions of substance abuse costs which are avoidable.

Research on avoidable costs may need to consist of a hybrid of more than one, and possibly all, of the above approaches. It should be acknowledged that the development of the methodology of estimation of avoidable costs is work-in-progress. It is expected that the publication of these guidelines will encourage pilot studies in a range of countries and for a range of drugs. The results of such studies should inform the research experience, which in turn will permit the improvement and refinement of these guidelines.

Bottom-line avoidable cost estimates are not the sole consideration in the determination of political priorities, nor should they be. There are a host of other considerations that policy makers and others involved in policy development should consider. However, economic cost studies provide an ideal framework for identifying key leverage points in policy development and for the development of priorities in research as well as for treatment, prevention and other interventions. The cost estimation symposia and international guidelines have done much to reduce differences in economic modelling and enhance the comparability of results of cost estimation studies in different countries. The current process of developing and refining avoidable cost guidelines will, hopefully, have a similar positive result. Despite the many sources of error in current cost estimates, it can be argued that it is indeed a valuable research exercise to estimate the costs of substance abuse and continually improve upon the methodology for conducting such studies. And ultimately, if appropriately qualified researchers do not do these cost studies well, others will do them badly, compounding the sorts of problems described here, while failing to provide the sort of benefits that good studies can do, and so simply adding to the confusion in a field which is already very difficult.