Initiation to the first drug use among substance-dependent persons in Iran.

In the present study, we report the initiation to the first drug in a representative sample of drug dependents in Iran. This is a cross-sectional study with a sample size of 7,743. The participants were characterized as drug dependents according to the Diagnostic and Statistical Manual-Fourth Edition and were sampled from the medical centers, prisons, and streets of the capitals of 29 provinces in the Islamic Republic of Iran.