Methods: Several administrative databases and surveys collected in Italy and in different EU countries concerning different sub-populations of drug users were analysed to estimate the permanence time in a specific drug using state and the stages of a typical drug-using career.
Results: Cannabis is mostly the first illegal substance used. The age at onset corresponds to the very beginning of adolescence and various sources indicate that this onset happens earlier for men than for women. For problematic drug users, the switch from cannabis to heavy drugs happens within a rather narrow period of time, within 5-6 years from the first use of cannabis, along with the first episode of drug dealing. The latency period distribution estimated from different data sources is quite stable, with men presenting longer latency periods than women.
Conclusions: The comparative analysis of several data sources allowed a more complete overview of the different subpopulations on the drug scene and provides interesting data to understand and to estimate parameters for dynamic models of drug use.