The lateral habenula as a master regulator of innate and learned social behaviors.

The lateral habenula (LHb) is classically associated with processing aversive stimuli and suppressing reward-driven behavior. Recent work, however, redefines the LHb as a node that not only mediates antisocial and avoidant behaviors but also regulates prosocial engagement and social motivation. As a convergence point for forebrain inputs and a driver of midbrain output, we review how the LHb contributes to behavioral outcomes in aggression, social avoidance, caregiving, and social memory. Cell-type-specific investigations reveal that glutamatergic (vGlut2⁺) and GABAergic (GAD2⁺) LHb neurons play dissociable roles in shaping aggression, social avoidance, and social cognition, while serotonin 2c receptor (5-HT) expressing neurons may represent a molecularly distinct sub-population differentially influencing social behaviors in males and females. These findings suggest that LHb circuits encode the valence and salience of social cues and flexibly adjust behavioral output in contextually appropriate and adaptive ways. Disruption of these pathways from stress, early adversity, or genetic susceptibility may underlie rigid or maladaptive social phenotypes. By mapping the input-output architecture and functional diversity of LHb subcircuits, future studies incorporating specific cell types and circuits will further unravel the complicated nature of how social decisions are dynamically regulated in the LHb and how dysregulated LHb activity may contribute to social symptoms of psychiatric disease.