Effects of non-pharmacological interventions on depressive symptoms and risk of major depressive disorder in adults with subthreshold depression: A systematic review and meta-analysis

Subthreshold depression (StD) is a condition that significantly reduces the quality of life and increases the risk of developing major depressive disorder (MDD). In order to investigate the effectiveness of non-pharmacological interventions (NPIs) in preventing the onset of MDD and improving depressive symptoms in adults with StD (AStDs), we conducted a systematic search of nine databases and included a total of 15 studies. Standardized mean differences (SMDs) were calculated using random effects models. RoB2 tool and GRADEpro software were used to assess the methodological quality and evidence. Funnel plots, Egger's, and Begg's tests were used to analyze publication bias. Sensitivity, subgroup and meta-regression analyses were performed to explore potential sources of heterogeneity. The results showed that NPIs had a significant effect in preventing the onset of MDD and improving depressive symptoms. Subgroup analysis revealed that NPIs were particularly effective in general adult populations, during short-term follow-up (FU) periods, among pregnant women, and in universal prevention programs. The results were found to be robust and credible, as they were less sensitive to changes in the analysis method. Timely detection and treatment of StD is feasible and important, as it can effectively delay or prevent the onset of MDD.