Five-Year Outcomes of a Dialectical Behaviour Therapy Skills Training Group Versus Supportive Group Training for Individuals With Nonsuicidal Self-Injury: A Randomized Controlled Study.

BACKGROUND

Nonsuicidal self-injury (NSSI) is common among adolescents and adults and is linked to depression, impulsivity and borderline traits, with increased suicide risk. Dialectical behaviour therapy (DBT) is widely used for NSSI, yet long-term evidence across age groups remains limited.

OBJECTIVE

To compare the long-term effectiveness of DBT skills groups (DBT-ST) versus social support group training (SSGT) for individuals with NSSI, and to characterize the durability of changes over up to 5 years.

METHODS

In this prospective randomized controlled trial, 47 individuals with NSSI were assigned to 13 weeks of DBT-ST or SSGT. Assessments were conducted at baseline, post-treatment, 1 year and 5 years using the HAMD-24, DERS, BIS and BSL-23, supplemented by the Chinese M.I.N.I. Intervention effects were analysed with linear mixed effects models and sensitivity analyses.

RESULTS

DBT-ST significantly improved emotion regulation in adults at 5 years (β = -27.97, p = 0.043), while adolescents showed fluctuating gains (β = +53.99, p = 0.003). Impulsivity declined in adults but rebounded in adolescents (β = +19.16, p = 0.026). Depressive symptoms improved by 74.0% in adolescents (β = -18.17, p = 0.020), and adults showed early remission. Borderline symptoms decreased substantially in adolescents (76.0%). Structured interviews confirmed greater reductions in depression (10 → 2) and BPD (17 → 5) in the DBT-ST group, though anxiety disorders increased, particularly among adolescents.

CONCLUSION

At the sample level, DBT-ST yielded larger and more durable gains than SSGT-primarily among adults-whereas adolescent effects were smaller, heterogeneous and not consistently significant. Long-term endpoints addressed symptoms and diagnostic status; NSSI episode frequency was not quantified longitudinally. Anxiety diagnoses increased in both arms, underscoring the need for routine anxiety screening and targeted management in future protocols.