Lonely minds in lonely bodies: Loneliness as insufficient psychological and neurophysiological self-other overlap.

Loneliness affects the health and wellbeing of a substantial proportion of the global population, posing a major public health concern. Loneliness, despite being an emotional state experienced within oneself, represents a sense of isolation from other individuals beyond the self. Most contemporary psychological research on emotion, especially in adults, takes an individualistic approach and is limited in accounting for "other" minds when studying the mind of a "self." On the other hand, studies of the neurophysiology of loneliness have mostly focused on presenting the biological correlates of loneliness, not accounting for the role of loneliness in representing pre-existing or anticipated biological needs. In this article, we review interdisciplinary research on self-other representation at levels of the mind, body, and brain. We propose neurophysiological mechanisms that support self-other overlap, guided by theories of allostatic-interoceptive self-regulation and situated in a predictive processing framework. These findings suggest that self-other representation in the body and brain may form a basis for social connection, and loneliness may be associated with insufficient self-other overlap. We discuss clinical implications of this model, especially in borderline personality disorder, and end with future theoretical and methodological considerations in advancing loneliness research.