This study examines whether a newly developed four-session psychosocial treatment program, called the First Step Program, can be delivered in real-world hospital settings to people receiving inpatient care for substance use disorders in Korea, and whether it shows early signs of benefit. The program combines motivational interviewing, acceptance and commitment therapy, and group activities, and is delivered twice a week over about two weeks (four 50-minute sessions). About 20 adults will take part at two psychiatric hospitals.

Participants complete brief questionnaires and a short interview about their motivation to change, craving, engagement in valued living, and social support before the program, immediately before and after each session, within one week after the program ends, and again at 1 month and 3 months after completion. After the program, some participants also join a small group discussion (focus group interview) to share their experience of the program.

Because this is a small, single-group preliminary (pilot) study without a comparison group, its primary purpose is to assess feasibility, that is, whether the program and the assessment approach work well enough, and to obtain preliminary effect and variability estimates to inform the design of a future large-scale randomized controlled trial.

Background: Substance use among the Korean population has increased rapidly, yet standardized, evidence-based psychosocial treatment programs and a corresponding clinician training and certification system are not well established in Korea. Evidence-based psychosocial interventions such as cognitive behavioral therapy, motivational interviewing, community reinforcement approaches, and 12-step facilitation are widely used as standard care in other countries, but comparable, locally validated programs are scarce in Korea. To address this gap, a Korean psychosocial treatment program (the First Step Program) was developed, and this preliminary study evaluates its feasibility and preliminary effectiveness.

Objectives:

1. Primary objective: to evaluate the real-world feasibility of delivering the First Step Program to inpatients with substance use disorders.
2. Secondary objective: to examine preliminary changes in motivation to change (URICA-DO), craving (VAS-C), engaged living (Engaged Living Scale), social support (2-Way Social Support Scale), and drug use history and treatment service utilization, and to assess whether these measures are suitable for a future comparative trial.
3. Tertiary objective: to explore participants' subjective experience and the acceptability of the program through a focus group interview, in order to refine the treatment manual and operational protocol for a future randomized controlled trial.

Design and setting: This is a single-arm, pre-post study with follow-up, without a control group. A total of 20 participants (10 per site) will be enrolled at two psychiatric hospitals that provide care to a large proportion of patients with drug use disorders in Korea (Incheon Chamsarang Hospital and Daegu Daedong Hospital). Study planning, rater training, informed consent storage, data management, and statistical analysis are coordinated centrally by the Catholic University of Korea. The two participating sites do not have their own IRB and are reviewed under the Uijeongbu St. Mary's Hospital IRB.

Intervention: The First Step Program consists of four 50-minute group sessions delivered twice weekly. The program integrates motivational interviewing, acceptance and commitment therapy, and group therapy. Session themes are: (1) treatment, choice, and personal values; (2) understanding the function of substance use and imagining alternative paths; (3) ambivalence and recovery-supporting relationships; and (4) charting a recovery direction and declaring a personal recovery plan.

Assessment schedule: Baseline assessment occurs within one week before the program. Craving is assessed immediately before and after each session, along with a stage-of-change rating, session satisfaction, and a treatment fidelity self-assessment. Post-intervention assessment occurs within one week after the program, followed by a focus group interview. Follow-up assessments are conducted at 1 month and 3 months after program completion.

Statistical analysis: Feasibility will be summarized using recruitment, retention, session attendance, and assessment completion rates. Change in continuous outcomes over time (pre, post, follow-up) will be analyzed using paired t-tests and linear mixed models; binary outcomes will be analyzed using McNemar's test and, where covariate adjustment for repeated measures is needed, generalized estimating equations. Missing data judged to be MCAR/MAR will be handled via maximum likelihood estimation within linear mixed models or multiple imputation, with sensitivity analyses. The main analysis is based on the full analysis set, with the per-protocol set as a supportive analysis. Qualitative focus group data will be transcribed and analyzed using thematic analysis (Braun & Clarke, 2006) by at least two independent coders.

Inclusion Criteria:

• Adults aged 19 to 65 years who can understand the study purpose and procedures and provide written informed consent
• Currently hospitalized (inpatient)
• Able to communicate and complete questionnaires in Korean
• Physically able to participate in program activities
• Has completed detoxification treatment
• Meets indication thresholds: DAST-10 score >= 2, URICA-DO precontemplation or contemplation stage, and >= 2 DSM-5 criteria

Exclusion Criteria:

• Cognitive impairment that precludes communication
• Physical conditions that preclude program participation (e.g., musculoskeletal disorder, severe cardiopulmonary disease)
• Acute psychotic symptoms or risk of self-harm or harm to others
• At risk of disrupting group activities such that focus group participation is not feasible
• Individuals who are inmates or incarcerated at screening are not enrolled; participants who become incarcerated after enrollment are withdrawn

This is a small, single-group pilot study involving sensitive data from patients with substance use disorders. Given the limited sample size and re-identification risk, individual participant data will not be shared. Only de-identified, aggregated results will be reported.