Systematic Review and Meta-Analysis of Self-Determination Theory-Based Interventions in Mental Health.

BACKGROUND: Self-Determination Theory (SDT) proposes that satisfaction of the basic psychological needs for autonomy, competence, and relatedness promotes psychological growth and mental health. However, previous evidence syntheses have largely examined psychopathology or well-being separately. The present systematic review and meta-analysis evaluated the effects of SDT-based interventions on mental health while separately examining mental illness outcomes and positive mental health (psychological functioning) within Keyes' dual-continua framework. METHODS: A systematic review and meta-analysis of 43 experimental and quasi-experimental studies was conducted. Random-effects meta-analyses estimated pooled intervention effects using study-level composite effect sizes for mental illness and positive mental health outcomes, while narrative synthesis summarized need-supportive intervention techniques. Moderator analyses examined participant, methodological, and intervention characteristics. RESULTS: SDT-based interventions demonstrated a large overall effect on mental health (g = 2.51). Separate analyses based on Keyes' dual-continua model indicated large effects for both mental illness reduction (g = 2.55) and positive mental health (psychological functioning; g = 2.48). Moderator analyses did not identify statistically significant differences according to participant, methodological, or intervention characteristics. Substantial between-study heterogeneity remained, warranting cautious interpretation of the pooled estimates. CONCLUSIONS: SDT-based interventions may promote holistic mental health by reducing mental illness outcomes while enhancing positive mental health (psychological functioning). Integrating these outcomes within Keyes' dual-continua model extends previous SDT evidence syntheses and highlights the potential of SDT as a theoretically grounded framework for promoting both recovery from psychological distress and positive psychological functioning.