Same movies, different stories: aberrant brain state dynamics during naturalistic emotional stimuli in depression

Affective social interaction relies on aligning emotional and cognitive responses with others, reflected in synchronized neural network states. Major depressive disorder (MDD), characterized by social withdrawal and emotional isolation, may impair this capacity. This study aimed to test whether individuals with first-episode, drug-naïve MDD exhibit disrupted shared neural representations during naturalistic emotional experiences, and to identify which specific brain-state dynamics underlie such alterations. Participants with MDD (n = 55) and healthy controls (HCs, n = 62) viewed happy and sad movie clips during functional MRI scanning. Using Hidden Markov Modeling, we identified eight recurrent brain states capturing large-scale network dynamics and compared inter-subject consistency, fractional occupancy, and transition patterns between groups. Compared with HCs, MDD presented unstable state transitions and reduced inter-subject consistency. During sad episodes, they were more likely to occupy limbic-dominant, self-referential states and less likely to return to externally oriented states prevalent in HCs. Patients also tended to transition into maladaptive, rumination-like states, reinforcing emotional isolation. Depression disrupts the formation of shared neural representations during collective emotional experiences. These findings provide a novel framework for understanding socioemotional dysfunction in MDD and highlight dynamic brain states as potential therapeutic targets for restoring interpersonal synchrony.