Index of WHO report . The relative risk of cannabis use, for example, is the increase in the odds of experiencing an adverse health outcome among those who use cannabis compared to those who do not. The population attributable risk represents the proportion of cases with an adverse outcome which is attributable to cannabis use. Relative risk is of most relevance to individuals attempting to estimate the increase in their risk of experiencing an adverse outcome if they use a drug.
Attributable risk is of most relevance to a societal appraisal of the harms of drug use.
The personal and public health importance of the two measures of risk magnitude depends upon the prevalence of drug use and the base rate of the adverse outcome. Conversely, an exposure with a high relative risk may have little public health importance because very few people are exposed to it but major personal health implications for those who are exposed. Consequently, an appraisal of the personal and public health importance of cannabis and other illicit drug use must take account not only of the relative risk of harm but also the prevalence of use and the base rate of the adverse effect. The Relative Risks of Adverse Health Effects of Cannabis Use Many of the quantitative risks of cannabis use can only be guessed at in the absence of studies of the dose-response relationship between cannabis use and the various adverse health effects. The following are guesstimates of the risks of cannabis use for the most probable adverse health effects.