This study addressed the uncertainty in the prevalence estimates of drug misuse in Dublin. Previous studies on treated drug misuse (O'Higgins, 1996) and on transmission of HIV and AIDS amongst Irish intravenous drugs users (Comiskey et al, 1992) produced very different prevalence figures. Opiate user is defined in the broad context to cover both problematic and non problematic users. In this study the capture-recapture method, including non-linear modelling, is used to estimate the prevalence of opiate use in Dublin. Anonymous identification data from three sources were used to obtain population samples. Using data on location of residence, prevalence is estimated for different locations in the city. In addiction an age based prevalence estimate of male and female opiate drug users is provided.

Results of prevalence estimates ranged from over 6,000 among medical data sources up to approximately 14,000 among the three data sources therefore it would seem prudent for planning purposes to assume in Dublin in 1996 there were approximately 10,500 - 12,500 opiate users. This figure is derived by averaging over the 95% confidence intervals of the 3 two sample estimates and the 1 three sample estimate. Not all of these may seek or be in need of treatment, looking at results derived from medical data alone it would appear that approximately 6,000-7,000 may require treatment. It should also be remembered that the majority of these users were found to be male and within the 15-24 year age range. To be specific a population of 13,460 opiate drug users in Dublin in 1996 between the ages of 15 and 54 inclusive was estimated from the three data sources. This corresponds to an estimated prevalence of 21/1000 or 2.1% of the population. The number of users within this age identified through the raw data alone was found to be 6,264, corresponding to a known prevalence rate of 10/1000 or 1% of the population. This estimate is in accordance with estimates published by other European cities.