Depression and LPP ERP Meta Analysis

There are several distinct theories regarding emotional dysfunction in depression, with each suggesting unique mechanisms regarding emotional processing difficulties in depression (i.e., negative potentiation theory, positive attenuation theory, and emotion context insensitivity [ECI] theory). The Late Positive Potential (LPP), an event-related potential component reflecting sustained attention to emotional stimuli, has been leveraged to evaluate competing theories of emotional processing in depression. Evidence from various psychophysiological studies employing the LPP has provided support for each of these prominent theories; however, the field currently lacks a comprehensive systematic review and meta-analysis that could clarify emotional processing dysfunction in depression revealed by the LPP. Therefore, this systematic meta-analytic review on the LPP effect in depression has two primary aims: (1) to determine the influence of stimulus valence (i.e., negative and positive) on the LPP effect size in depression; and (2) to assess whether factors such as experimental methods, sample clinical characteristics, and sample demographics moderate these LPP and depression relationships. A systematic computerized literature search of PubMed and ProQuest was conducted for published and unpublished studies from 1981 to 2024.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 resulting in 183 effect sizes (i.e., 83 depression and positive LPP; 100 depression and negative LPP). Robust variance meta-regression results revealed a small significant negative effect size (r = -.06) between LPP elicited by positive stimuli and depression, while no significant relationship was initially observed between LPP elicited by negative stimuli and depression. Moderator analyses indicated that LPP time window and age impacted the positive LPP and depression effect size, while comorbidity status moderated the negative LPP and depression effect. Regarding limitations, we did not exhaustively test all possible factors that may impact LPP and depression association due to a lack of standardized reporting and available data. Findings presented herein primarily support the positive attenuation theory, with inconclusive evidence for the negative potentiation and ECI theories of depression.