Estimated Prevalence of Heroin Use in Spain, 2011

"The estimates of problem use indicate that the total number of problem heroin users (prevalence) peaked in Spain in the early 1990’s with more than 150,000 heroin users, as of which time these numbers began to decline.
"Due to the small number of heroin users found in the samples, it is practically impossible to obtain reliable estimates directly from the population-based surveys as to the percentage of users who have started treatment for this substance and to be able to apply the in-treatment multiplier method. However, previously, in the 2007 Household Survey on Alcohol and Drugs in Spain (EDADES), the nominative method, a variation on the in-treatment multiplier method, was employed.
"To date, problem heroin users have therefore been being estimated by using the multiplier figures found in the 2007 Household Survey on Alcohol and Drugs in Spain (EDADES) and by applying this multiplier to the data available regarding treatment in Spain (indicator of admissions to treatment, users who have undergone treatment at outpatient centres and number of users in treatment with opiate maintenance) for the years 2006, 2007, 2008 and 2009.
"In 2011, the Household Survey on Alcohol and Drugs in Spain (EDADES) once again included the questions necessary so as to be able to apply the nominative method, thus making it possible to update the in-treatment multiplier. For this purpose, those surveyed were asked whether they knew any heroin users, and for each one of the heroin users they knew, those surveyed were to indicate if they knew whether or not those in question had started treatment for dependence on this drug within the last 12 months.
"Thus, valid answers were obtained on 1427 reported users, a total of 643 (45%) of whom had started treatment for dependence according to those surveyed. By applying this multiplier to the 17,325 'individuals admitted to treatment for heroin in 2010', the figure of 38,500 problem heroin users is calculated."