Effectiveness of an online positive affect treatment targeting reward sensitivity in reducing depressive symptoms...

Low positive affect and deficits in reward sensitivity are core features of depressive symptoms, yet they are rarely addressed in traditional psychotherapies. This study examined the effectiveness of an internet-based Positive Affect Treatment (iPAT) in improving depressive symptoms, anxiety symptoms, and reward sensitivity, as well as the longitudinal mediation effect of dynamic changes in reward sensitivity. Eighty-eight individuals with depressive symptoms were enrolled in a randomized controlled trial and randomly assigned (1:1) to either an intervention group or a waitlist control group. The 6-week iPAT intervention was delivered via a WeChat mini program. The feasibility and acceptability of iPAT were evaluated, and participants completed seven assessments (baseline and weekly for six weeks) measuring depressive symptoms, anxiety symptoms, and reward sensitivity. Intervention effectiveness was analyzed using a generalised linear mixed model, and longitudinal mediation was examined using latent growth curve modeling. Results showed that iPAT significantly reduced depressive symptoms and enhanced reward sensitivity. Moreover, the mediation analysis revealed that the rate of change in reward sensitivity fully mediated the relationship between the intervention and reductions in depressive symptoms. iPAT demonstrated good feasibility and acceptability. To our knowledge, this is the first study to show that internet-based Positive Affect Treatment can alleviate depressive symptoms by enhancing reward sensitivity. These findings support reward sensitivity as a key mechanistic target for precision psychological interventions and suggest that iPAT offers a scalable digital solution for the indicated prevention of depression, targeting individuals with early or subthreshold symptoms to prevent further progression. Registration identifier: ChiCTR2400095048.