Background: Event-related potentials (ERPs) offer insights into neural mechanisms underlying bipolar disorder (BD), but their role as stable trait markers or state-dependent indicators remains unclear.
Methods: We examined six participant groups: healthy controls, individuals with BD I and II in depressed or euthymic states, and their unaffected siblings during an emotional visual task. Participants viewed images with negative, positive, or neutral emotional valence, each surrounded by a green or red frame. They were instructed to press a key matching the frame's color. EEG data were recorded, and effects of participant group and emotional valence on task performance and ERP characteristics (amplitude and latency) were evaluated using linear mixed-effects models, corrected for age and gender.
Results: Response time showed a significant group × condition interaction (Δχ2(22) = 34.33, p < 0.001), with predicted RTs from 579 ms (95 % CI: 452-743) for the BD_II euthymic group in the neutral condition to 829 ms (95 % CI: 732-940) for BD_I depressed participants in the negative condition; however, no post hoc differences remained significant after FDR correction. Early (N200) and late (LPP; 600-1000 ms) ERP amplitudes varied by condition, and P300 latency differed between groups, with unaffected siblings showing ERP alterations compared to controls.
Conclusion: BD, its subtypes, and mood states exert distinct effects on early and late ERP characteristics during emotional processing. These findings support the potential use of ERP features from emotional tasks as diagnostic markers for BD and highlight the complex interplay between trait and state factors in BD's neurophysiological profile.
Keywords: Bipolar disorder; Emotional processing; Endophenotypes; Event-related potentials; Neurophysiology.
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