Background and objectives: Relapse after treatment is a common problem among drug addicts in addiction control and prevention programs. About 80% of the addicts relapse into drug abuse within 6 months after treatment. The purpose of this study was to determine factors associated with drug abuse relapse in patients consulting two selected addiction treatment centers in Tehran. 

Material and Methods: In this case-control study, 160 relapsed patients were compared with 160 abstentious patients. A researcher-developed questionnaire was used to collect data. Chi-square test, odds ratio (OR) and logistic regression were performed for data analysis.

Results: The findings showed that factors increasing rate of relapse were smoking after relapse (OR=7.14, CI=3.855-13.244), substance-related cues (OR=6.76, CI= 3.915-11.678), interaction with addict peers (OR=6.38, CI=3.921-10398), malaise (OR=3.93, CI=2.446-6.305), and family conflict (OR=2.04, CI=1.227-3.385). Opium- and dross-addicts were found to be less likely to have a relapse than crack- or pot- users (OR= 0.208, CI-0.128- 0.336). 

Conclusion: The findings of this study reveal that relapse into drug abuse is significantly associated with personal, social, psychological and medical variables. It is recommended to 

integrate family counseling and therapeutic approaches, constant monitoring, and health care in treatment plans in order to reduce the adverse effects of factors such as family conflicts, peer pressure and drug-related cues in patients' likelihood of relapse.