use drugs, and thirdly that strategies are included which demonstrate that, on the balance of probabilities, it is likely to result in a net reduction in drug-related harm” (Lenton and Single, 1998). Frequently definitions assess alternatives not in aggregate health measures but in terms of the harms associated with a single act or product or with the individual user; for example, “the term harm reduction originally referred to only those policies and programmes which attempted to reduce the risk of harm among people who continued to use drugs” (Lenton and Single, 1998, citing Single and Rohl, 1997).

The harms consist of all the adverse consequences borne by members of society. These include increased morbidity and mortality (among both users and nonusers) from all sources; addiction itself; expenditures on regulation or enforcement, since these are costs borne by taxpayers; the increased intrusiveness of the state; and crime that might be generated by regulation or enforcement or by the behavior itself.

These adverse consequences are borne by many different groups: users themselves; intimates of the user, particularly children and spouses; nonusers directly (e.g., through crime, in the case of illicit drugs, or traffic accidents in the case of alcohol); and nonusers indirectly or society generally (e.g., through taxation). The value society gives in considering interventions to the interests of these groups may vary (MacCoun et al., 1996); typically a greater consideration is given to the welfare of children or of neonates, since they are the most vulnerable victims, with very limited capacity to undertake actions in their own interests.

Analytics

Total harm can be expressed as a function of the number of individuals engaged in the behavior and the damage each causes. In turn, the damage caused by an individual is a function of intensity of use (or frequency of behavior) and of the harmfulness of each episode of use or behavior. MacCoun and Reuter (2001) suggest that total harm can then be expressed as

Total Harm=Harmfulness (per use)×Intensity (per user)×Prevalence (of use)

It can be reduced through declines in any of the three components individually, including intensity.

However the three components may not be independently determined. In particular, prevalence may be affected by harmfulness through three distinct, though related, paths; initiation, nondesistance, and relapse. The lower harmfulness may reduce perceived harmfulness and encourage someone to begin using drugs, to drive a car too fast, or engage in sex at too early an age. Perceived dangers may be influenced both by the actual



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