"Heroin has been, at least until very recently, the principal drug problem for Switzerland, as for most Western European nations. In the mid-1990s Switzerland had a heroin addiction prevalence that may have been the highest in Europe. Switzerland’s heroin problem has been declining steadily over the last decade. The estimates of the size of the group are crude but show a reduction from about 29, 000 in 1994 to 23,000 in 2002, the most recent year for which an estimate is available. The aging of the population in treatment is a reassuring indicator that initiation rates have been low since the mid-1990s; whereas in 1994 the median age of those in treatment was 26.5 years, that had risen to 30.5 by 2006. The health of the heroin dependent population has been improving."
Peter Reuter and Domenic Schnoz. "Assessing Drug Problems and Policies in Switzerland, 1998-2007." Swiss Federal Office of Public Health. November 16, 2009.