A PRISMA-compliant systematic review and meta-analysis of the late positive potential in depression

There are several theories regarding emotional dysfunction in depression, with each suggesting unique emotional processing difficulties in depression. The Late Positive Potential (LPP) has been leveraged to provide insight into these theories of emotional processing in depression. The field currently lacks a comprehensive systematic and meta-analytic review that could clarify emotional processing dysfunction in depression revealed by the LPP. This systematic meta-analytic review on the LPP effect in depression has two primary aims: (1) to determine the effects of stimulus valence (i.e., positive, negative, and neutral) on the LPP effect size in depression; and (2) to assess whether factors such as experimental methods, sample clinical characteristics, and sample demographics moderate the relationship between the LPP and depression. A systematic computerized literature search of PubMed and ProQuest was conducted for published and unpublished studies from 1981 to 2024. A total of 51 studies (total N = 4,517) comprised the final analyses. Robust variance meta-regression results revealed a small significant negative effect size between LPP elicited by positive stimuli and depression. Moderator analyses further indicated that the positive LPP and depression effect size was stronger in the early LPP time windows and in adult samples. Comorbidity status moderated the association between depression and the negative LPP such that a small significant negative effect size was observed in samples with comorbid internalizing disorders. Findings presented primarily support the positive attenuation theory, with partial evidence for the emotion context insensitivity (ECI) theory.