en مطالعات اعتیاد Addiction پژوهشي Original Research Articles <div style="text-align: justify;"><strong>Objectives:</strong> In this study, we aimed to determine the individual characteristics of clients who were referred to residential rehabilitation centers for drug use disorders and to determine their relapse-related factors.<br> <strong>Methods:</strong> This cross-sectional study was conducted on 576 patients who were referred to nine residential treatment centers for drug use disorders, chosen by the cluster sampling method. A self-constructed questionnaire to assess personal and addictive characteristics was applied. Data were analyzed using descriptive statistics and Independent t-test. Multiple regression models were applied to determine the factors affecting the time of relapse.<br> <strong>Results: </strong>The average interval between quitting drug use and relapse was found to be 4.7 months with a standard deviation of 4.1. Age and relapse were found to be correlated (0.193), but the correlation was not found to be statistically significant (P=0.12). There was significant correlation between occupational status (P=0.014) and number of attempts to quit drug use (P=0.019) with relapse. In addition, there were significant correlations between relapse time with injection history (P=0.035), victim&rsquo;s history (P=0.047), risky sexual behaviors (P=0.022), sexual dysfunction (P=0.019), having a consumer as a close friend (P=0.001), another drug user in family (P=0.001), compulsory treatment (P=0.033), and alcohol consumption (P=0.041). There was no significant relationship between relapse with duration of addiction, type of abused drug, education, staying longer in centers, and marital status.<br> <strong>Discussion: </strong>There is a high chance of relapse in case of patients who seek treatment in residential rehabilitation centers for drug use disorders. Paying attention to the patients&rsquo; social status and especially their occupation and connection with the treatment center after discharge reduces possibility of relapse.</div> Drug dependence, Residential treatment center, Drug use disorder, Relapse 139 146 http://irj.uswr.ac.ir/browse.php?a_code=A-10-348-20&slc_lang=en&sid=1 Omid Massah omchomch@gmail.com 0000-0002-9688-9144 No Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Farhad Taremian fa.taremian@uswr.ac.ir 0000-0002-0736-2608 Yes Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Reza Moloodi k.moloodi@gmail.com 0000-0002-8384-9565 No Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Mohammad Hassan Farhadi mhfarhadiir@yahoo.com 0000-0001-9392-9078 No Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Elaheh Ahounbar e.ahounbar@yahoo.com 0000-0002-2744-2656 No Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.