Recovery Outcomes and Treatment Dropout in Patients with Complex Problems Undergoing Inpatient Addiction Treatment: A Naturalistic Prospective Cohort Study

Introduction: Recovery from substance use disorder (SUD) spans clinical, functional, and personal dimensions. However, research covering these domains, particularly in populations with complex problems such as those with mild to borderline intellectual disabilities (MBIDs), remains limited. This study explored different recovery outcomes and their relationship with treatment dropout during the first 12 weeks of inpatient treatment, while also examining whether the presence of MBID affected the outcomes. Methods: A naturalistic, prospective cohort study was conducted with patients undergoing inpatient SUD treatment at a Salvation Army Clinic in The Netherlands. Recovery outcomes (clinical, functional, personal) and predictors of dropout were assessed over 12 weeks. MBID (yes/no) was determined using the SCIL screening tool. Data were analyzed using repeated measures (M)ANCOVA to evaluate recovery trajectories and logistic regression to explore associations between recovery levels and dropout. Results: Of the 157 participants, 66% screened positive for potential MBID, and 40% dropped out within 12 weeks. For completers, significant improvements were observed across all recovery domains over time (all p < 0.001). Psychological problems decreased by a mean of 9.6 points (95% CI: 7.5–11.8), physical problems by a mean of 3.7 points (95% CI: 2.0–5.4), and craving by a mean of 7.5 points (95% CI: 6.4–8.6). Functional recovery increased by a mean of 5.1 points (95% CI: −1.4 to 11.7), and personal recovery by a mean of 5.7 points (95% CI: 3.5–7.9). Lower baseline recovery levels were associated with greater relative improvements but lower endpoint scores. Lower baseline functional recovery was a small but significant predictor of dropout. MBID status did not affect recovery trajectories. Conclusions: The findings suggest a multidimensional recovery process during early phases of inpatient treatment, irrespective of MBID status. Baseline recovery levels play a crucial role in shaping outcomes, underscoring the importance of early assessments. Importantly, these findings indicate that those worst off at baseline profit most from treatment.