Table 1. Means and Standard Deviations for the Duration of Retention in the Program per Week.

Variable	Retention, wk a	P Value b
Prison		< 0.001
Isfahan	23.5 ± 0.9
Hamadan	11.3 ± 1.0
Tehran	26.4 ± 0.3
Drug injection		0.008
Yes	25.9 ± 0.7
No	21.9 ± 0.8
Main used drug		0.001
Opium/opium extract	18.6 ± 3.1
Heroin and crack	24.6 ± 0.6
Ecstasy	25.9 ± 1.0
Other drugs	9.8 ± 0.9
HBV test		0.02
Negative	25.0 ± 0.6
Positive/unknown	23.1 ± 0.8
Occupation/income		0.05
Stable job / regular income	22.7 ± 1.1
Instable job / irregular income	24.1 ± 0.6
Main cause of imprisonment		< 0.001
Drug-related crime	25.8 ± 0.6
Crimes not related to drugs	18.4 ± 1.5
History of involvement in harm reduction programs		< 0.001
Yes	19.9 ± 1.2
No	25.7 ± 0.6

^a Data are presented as Mean ± SD.

^b Log-Rank Test.