A systematic review and meta-analysis examined the relationship between user engagement and clinical outcomes in apps designed for depression and anxiety. The study analyzed 28 trials, with 13 included in the meta-analysis, focusing on how engagement metrics correlated with symptom improvement. Researchers identified over 40 different engagement metrics, with more than half of the studies examining multiple predictors. The analysis revealed a significant pooled effect, showing that greater user engagement was associated with larger symptom improvement (r = 0.16). This effect remained significant after adjusting for publication bias, with a slight decrease when accounting for studies that reported non-significant associations without data (r = 0.11). Additional analyses indicated significant effects when examining specific engagement metrics, symptom outcomes, and app characteristics, though contributions to these analyses were limited. The findings suggest that while engagement may play a small role in improving symptoms, better reporting standards are needed to clarify which engagement metrics should be consistently utilized in future research.