Objective: This Randomized Controlled Trial (RCT) aimed to examine the effectiveness of a mindfulness-based relapseprevention program with problem-solving solution skills (MPSS) for male substance users on stress, deliberate self-harm, and drug-abstinence intention.

Material and Methods: Thirty-six male substance users aged 18–59 were recruited from a rehabilitation institute in Thailand and randomly assigned to the intervention and control groups equally. The MPSS was based on a mindfulness program with added problem-solving skills. Implementation included 8 sessions over a four-week period at the setting site, and a follow-up and an assessment were delivered via a mobile phone. Data were collected 3 times: at pre-intervention (week 0, T1), post-intervention (week 4, T2), and follow-up (week 6, T3). A three-month assessment followed in order to determine any addiction relapse. The Thai Perceived Stress Scale-10, the Revised Deliberate Self-Harm Inventory, and the Drug Abstinence Intention Questionnaire were used to assess the main outcomes. The reliability values were 0.82, 0.81, and 0.86, respectively. A two-way repeated measures ANOVA was used to determine the outcome differences between the groups and times.

Results: After completion of the intervention, participants in the intervention group had significantly higher drug-abstinence intentions and lower deliberate self-harm both at T2 and T3. They had lower stress at T3 than the control group. The intervention group underwent no emotional, mental or physical relapse 3 months after the program’s completion. The control group had about a 60% relapse rate.

Conclusion: These findings indicate that an MPSS is effective in lowering stress and deliberate self-harm, and increasing drug-abstinence intention without emotional, mental or physical relapse in male substance users.