Understanding readmission to substance use disorder treatment in Chile: a mixed-method study

<i>Background:</i> Healthcare readmissions are often perceived as negative outcomes. However, in the context of substance use disorder (SUD) treatment, they may reflect both systemic gaps and sustained engagement. Despite their frequency, the determinants of SUD readmission remain underexplored, particularly in Latin America, where non-injected drug use is highly prevalent.<i>Objective:</i> To identify factors associated with SUD treatment readmission and examine contextual influences shaping readmission risk in Chile.<i>Method:</i> We employed a mixed-methods parallel convergent design. Quantitative analyses included 107,559 treatment episodes (84,978 males; 22581 females) recorded from 2010 to 2019. We estimated Average Hazard Ratios (AHR) using a PWP-GT model. Qualitative data from 14 in-depth interviews explored social, familial, and environmental contributors to readmission.<i>Results:</i> Compared to those who did not complete, completing ambulatory treatment was associated with a lower risk of readmission (AHR = 0.83, 95% CI: 0.78-0.88), while no significant effect was found in residential programs. Women had a higher risk of readmission than men in both ambulatory (AHR = 1.36, 95% CI: 1.31-1.42) and residential settings (AHR = 1.42, 95% CI: 1.33-1.51). Qualitative findings revealed reintegration difficulties post-discharge, especially in high-risk environments. Gender roles pressured women to seek treatment, particularly when they were primary caregivers.<i>Conclusion:</i> Support for caregiving responsibilities may enhance treatment retention and reduce readmissions among women. Clinicians and policymakers should consider implementing structured post-discharge follow-up and community-based support systems, especially after residential treatment, to mitigate environmental risks and sustain recovery.