For better and worse: neural self-partner overlap during social feedback is associated with relationship satisfaction and depressive symptoms.

In close relationships, the boundary between self and partner can blur-a phenomenon known as self-other overlap. This overlap may be especially pronounced during social-emotional contexts, where partners share one another's joys and distress. Yet little is known about how the brain represents this overlap during social-emotional experiences. More specifically, it is unclear whether it differs by emotional valence, whether it relates to relational and personal well-being, and whether these associations vary across social-emotional contexts. To address these questions, we scanned 90 romantic couples (n = 180) processing positive and negative social feedback directed toward themselves or their partners. We assessed neural self-partner representational similarity (RS) in the ventromedial prefrontal cortex, a region implicated in self-referential processing. Participants showed greater self-partner RS during negative than positive feedback. Across both valences, higher RS was associated with greater partner-reported relationship satisfaction. Under negative feedback, greater RS was associated with higher concurrent relationship satisfaction for both partners via daily support provided to the partner, as well as higher self-reported concurrent and 6-month depressive symptoms via daily affect. These findings reveal the mechanisms through which neural self-other overlap simultaneously relates to relational closeness and emotional risk under distressing conditions.