This study examines whether a newly developed eight-session psychosocial treatment program, called the Emotion Regulation 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 four weeks (eight 50-minute sessions). About 20 adults will take part at two psychiatric hospitals.

Participants complete brief questionnaires and a short interview about their craving, motivation to change, difficulties in emotion regulation, self-compassion, depression, and drug use history 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, with spread into adolescents and people in their twenties. 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 Emotion Regulation 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 Emotion Regulation Program to inpatients with substance use disorders.
2. Secondary objective: to examine preliminary changes in craving (VAS-C), motivation to change (URICA-DO), difficulties in emotion regulation (DERS-SF), self-compassion (K-SCS), depression (PHQ-9), 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 program consists of eight 50-minute group sessions delivered twice weekly over approximately four weeks. It integrates motivational interviewing, acceptance and commitment therapy, and group therapy, and draws on emotion-regulation and self-compassion skills. Session themes are: (1) understanding emotions and following the body's signals; (2) emotion regulation strategies I: grounding oneself through the senses when shaken; (3) emotion regulation strategies II: practicing choice rather than being swept away by emotion; (4) building a personal emotion-response scenario for moments of crisis; (5) facing the self-critical voice; (6) protecting oneself with warmth in difficult moments; (7) noticing and savoring positive moments; and (8) organizing a personal emotion-regulation routine to sustain going forward.

Assessment schedule: Baseline assessment occurs within one week before the program. Craving is assessed immediately before and after each session, along with session satisfaction and a therapist 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 repeated-measures analysis of variance and linear mixed models; where covariate adjustment for repeated measures is needed, generalized estimating equations will be used. Analyses adjust for sociodemographic covariates and indication variables, or use stratified comparison. 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 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

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.