"The lifetime prevalence is not suitable as an indicator for current changes since it does not give any valuable clues to the current use behaviour of the interviewees. In literature, the 12-month prevalence is generally used as a reference value since, on the one hand, it is referred to a reasonably limited time window of past use and, on the other, it provides interpretable prevalence values (whereas the 30-day prevalence of the use of illicit drugs with the exception of cannabis often only gives extremely low figures) (details on the population surveys are also contained in the online standard table 1).
"While the lifetime prevalence of the use of illicit drugs among adults in the age group 18-64 years (ESA [Epidemiological Survey on Addiction]) slightly increased between 2006 and 2009 (2006: 23.7%; 2009: 26.7%), the figures for the use of illicit drugs in the 12-month category remained practically unchanged between the two data collection years 2006 and 2009 (2006: 5.0%; 2009: 5.1%). The situation is similar for the use within the last 30 days prior to the survey (2006: 2.5%; 2009: 2.6%) (Pabst et al. 2010).

"As the prevalence of the use of illicit drugs (total) significantly depends on the use experience with cannabis (and is nearly the same), the findings of the ESA 2006 indicate a stabilisation of the decline of the current use of cannabis in the general population, which had already been observed by the ESA 2006. Within the framework of the ESA 2009, only 7.4% of the interviewees (2006: 5.8%) report experience with other illicit drugs in the lifetime category. Even lower are the values for the 12-month (1.3%) and 30-day prevalence (0.6%), which have remained practically unchanged in comparison with the survey carried out in 2006 (1.2% and 0.7% respectively) (cf. also Table 2.2)."


German Reference Centre for the European Monitoring Centre for Drugs and Drug Addiction (Deutsche Beobachtungsstelle fuer Drogen und Drogensucht (DBDD)), "2012 National Report to the EMCDDA by the Reitox National Focal Point: Germany: New Developments, Trends and In-Depth Information on Selected Issues - Drug Situation 2011/2012" (Munich, Germany: DBDD, Oct. 2012), p. 29.