Limitations
MH, opioid use disorder
BLIND
To interpret the findings, there are some limitations in the present study that should be considered. First, this clinical trial was conducted in only one addiction treatment clinic located in an urban area of ​​Iran, which could reduce the generalizations to all patients with opioid use disorder undergoing MMT. Second, the PoR and MH here were assessed using self-report scales; however, the implementation of objective methods could be more beneficial in better assessing the impact of such intervention programs. Third, the effect of zinc supplementation in the present study on the PoR and MH status was not measured at long intervals after the completion of the intervention program (of note, the intervention lasted three months). Finally, the nature of the intervention in this study made it difficult to blind the participants.