Background/Objectives: Suicidal ideation and non-suicidal self-injury (NSSI) among elementary school students represent critical public health concerns that require develop-mentally appropriate, evidence-informed school-based interventions. This study con-ducted a retrospective comparative analysis of two school-based approaches—Sandplay Therapy with Suicidal Ideation and Self-Injury-Focused Engagement (SPT-SAFE) and a School-based Dialectical Behavior Therapy-informed Brief Intervention (DBT-BI)—for elementary school students presenting with suicidal ideation and NSSI. The objective was to describe pre–post-changes in key outcomes within each intervention and to explore whether outcome trajectories differed between the two approaches in a non-randomized, real-world school-based setting. Methods: This retrospective study analyzed archival clinical records from 109 elementary school students (SPT-SAFE: N = 59; DBT-BI: N = 50) who received services at a school-based suicide prevention center in South Korea between 2022 and 2024. Seven validated outcome measures assessed suicidal ideation, NSSI frequency, depression, anxiety, aggression, impulsiveness, and self-concept at pre- and post-intervention. Pre–post-changes and exploratory between-group differences were examined using 2 × 2 mixed-design ANOVAs (Group × Time interaction), with baseline-adjusted ANCOVAs conducted as complementary analyses. Suicidal ideation was operationalized using the SIQ-JR total score, and NSSI was operationalized using the FASM summed frequency index. Results: Both interventions were associated with significant reductions in suicidal ideation (F = 29.98, p < 0.001, partial η2 = 0.219) and NSSI frequency (F = 15.95, p < 0.001, partial η2 = 0.130), with large within-group effect sizes and no significant Group × Time interactions. Accordingly, between-group differences were limited and should be interpreted as exploratory rather than comparative–effectiveness evidence. Modest between-group differences favoring DBT-BI were observed for self-concept outcomes (F = 4.14, p = 0.044, partial η2 = 0.037; d = −0.39). Conclusions: These findings suggest that both interventions were associated with pre–post-improvements in suicidal ideation and NSSI frequency within a school-based clinical context.
Kwak et al. (2026) studied this question.