Impact of a preadmission consultation on inpatient treatment adherence among patients with substance use disorders: a retrospective cohort study

Background Substance use disorders are associated with poor adherence and premature discharge. Preadmission consultations aim to improve engagement before inpatient detoxification, yet their impact remains undocumented.Objectives To evaluate the impact of a preadmission consultation on inpatient adherence and identify associated factors.Methods Retrospective single-center study of two cohorts hospitalized at the Centre Hospitalier Universitaire (CHU) Tivoli (Belgium): control group (n = 224, February 2021–February 2022) and preadmission group (n = 149, May 2023–May 2024). Four adherence indicators: discharge against medical advice, involuntary discharge, post-detoxification transfer, and length of stay. Secondary analyses examined substance type, comorbidities, housing, employment, age, and prior detoxification.Results The preadmission group was more frequently male (75.2% vs. 63.0%, p = 0.013), homeless (22.8% vs. 10.7%, p = 0.002), and had higher rates of crack cocaine (31.0% vs. 8.9%, p < 0.001) and polysubstance use (49.7% vs. 38.8%, p = 0.039). Post-treatment transfers (13.4% vs. 7.1%, p = 0.044), stays ≥20 days (47.0% vs. 34.4%, p = 0.015), and involuntary discharges (18.1% vs. 10.7%, p = 0.041) were more frequent in the preadmission group. Discharge against medical advice did not differ. Cocaine, cannabis, and polysubstance use predicted discharge against medical advice; cluster B personality disorder and cannabis use were associated with shorter stays.Conclusions The preadmission consultation may support care pathways and post-detoxification transitions. However, results warrant caution: discharge against medical advice was unchanged, involuntary discharges increased, and the preadmission group was more clinically complex. Whether observed benefits reflect the intervention or selection bias is unclear. Prospective studies are needed.