Background: The hidden nature of the use of opioids, amphetamines, cocaine, and cannabis (the most
commonly used and studied illicit drugs) precludes the accurate estimation of how many people use them and further
important aspects of the use. Among the many aspects of drug use, the permanence times in specific drug using states
related to the lifestyles of the various sub populations of users are of interest, per se, as essential components of estimates
relating prevalence and incidence of drug use and for evaluating policies.
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.