Examining the malleability of research domain criteria positive valence system constructs in mood disorders: A systematic review and meta-analysis

Anhedonia is a core symptom of mood disorders that remains inadequately addressed by first-line treatments. It is mechanistically tied to impairments in reward processing, encompassing reward responsiveness, reward valuation and reward learning, which are formalised within the Positive Valence System (PVS) domain of the Research Domain Criteria framework. However, evidence is mixed regarding the malleability of these reward processes and their viability as treatment targets for anhedonia. This systematic review and meta-analysis examined whether self-report and behavioural measures of PVS constructs change following treatment and control conditions in individuals with mood disorders. A systematic search of four databases identified 80 eligible studies reporting relevant pre-post data. Multilevel random-effects meta-analyses were conducted, with study condition, PVS construct, and outcome prioritisation included as moderators. Across 179 self-report outcomes from 71 studies, a large improvement in reward processing was observed when treatment and control conditions were combined (g = 0.74, 95% CI [0.64, 0.85]), with treatments showing a significantly greater improvement than controls. Among reward constructs, reward valuation showed greater change than reward responsiveness and reward learning. Outcome prioritisation showed no moderating effect. In contrast, the effect across 31 behavioural outcomes from 16 studies was small (g = 0.17, 95% CI [0.02, 0.33]). Exploratory analyses revealed significantly greater improvements in self-report than behavioural measures. These findings suggest that reward processes are malleable and may represent viable treatment targets for anhedonia. However, differences in malleability across PVS constructs and self-report versus behavioural measurement modalities highlights the need for methodological refinement and further research.