Evaluating treatment outcomes across four substance use treatment settings: a 12-month longitudinal study in Iran

Substance use disorder is a persistent public-health challenge in Iran, where multiple treatment settings operate in parallel. This study assessed within-modality changes over 12 months among clients in Methadone Maintenance Treatment (MMT), Drop-in Centers (DICs), Therapeutic Communities (TCs), compulsory (Article 16) treatment.

A prospective, naturalistic cohort was conducted across 15 routine-care centers in Kerman Province (May 2023-May 2024). Of 493 enrolled, 470 completed follow-up (MMT/DIC at 12 months; TC/compulsory at end-of-treatment [EOT]). MMT/DIC were assessed at baseline, 2 months, and 12 months; TC/Article 16 at baseline and EOT. Outcomes were assessed using the Maudsley Addiction Profile (MAP). Within-modality changes from baseline were estimated with mixed-effects models in Stata 15, using two-sided tests (α = 0.05).

MMT was associated with reductions in alcohol, opium, and heroin use, lower odds of interpersonal conflicts, fewer physical/psychological problems, and fewer days of illness-related unemployment. DIC showed decreases in physical/psychological problems, drug-related harms (e.g., dealing), and fighting; changes in spouse/relative/friend-conflict indicators were not statistically significant. TC showed short-term reductions in several substances; employment decreased during the residential phase (a programmatic constraint rather than a change in employability). Article 16 showed declines in selected substances and health problems during observation; durability post-discharge remains uncertain.

Findings indicate domain-specific, within-modality changes rather than comparative effectiveness between settings. In TCs, short-term within-modality declines were observed in alcohol and selected illicit opioids at EOT alongside limited employment opportunities during residence due to programmatic restrictions. Within MMT, improvements were observed in selected psychosocial indicators at follow-up, consistent with stabilization during ongoing care. Within DICs, reductions were observed in health problems and certain risk behaviors, aligning with their harm-reduction and linkage role. Within Article 16, short-term declines were observed in selected substances and health problems during observation; durability after discharge is uncertain without structured aftercare. Overall, no single modality appears universally superior; matching clients to treatment according to target outcomes, and implementing stepped-care or blended pathways with robust post-treatment supports-particularly following compulsory programs-may optimize long-term impact.