Estimating incidence of problem drug use using the Horwitz-Thompson estimator - A new approach applied to people who inject drugs in Oslo 1985-2008

This new method, which incorporates temporarily inactive problem drug users, may become a useful tool for estimating the incidence of problem drug use over time. The method may be less data intensive than other methods based on first entry to treatment and may be generalized to other groups of substance users. Further studies on drug use progression would improve the validity of the results.