Developmental adversity, as treated across the depth-psychology and developmental neuroscience corpus held in this library, names the broad field of early-life stressors—neglect, abuse, attachment disruption, prenatal trauma, institutionalization, and interpersonal violence—that interact with biological maturation to shape the emerging mind, brain, and soma in lasting ways. The literature does not speak with a single voice. Siegel frames developmental adversity primarily through a neurobiological and relational lens, arguing that the social environment drives gene expression and neural architecture during critical windows, making early stressors capable of structural, epigenetic, and functional reorganization of the brain. Lanius and colleagues stress the heterogeneity of adversity types—verbal abuse, sexual abuse, neglect, caregiver disruption—each carrying distinct neurobiological signatures and windows of maximal sensitivity. Van der Kolk, Ford, and Spinazzola formalize the psychiatric sequelae under the rubric of Developmental Trauma Disorder, emphasizing that the comorbidity profile of developmentally traumatized children exceeds what PTSD alone can capture. Heller attends to the phenomenological and somatic consequences—disconnection, identity distortion, affect dysregulation—foregrounding the pre-verbal, relational origins of character pathology. Yehuda extends the frame transgenerationally, demonstrating epigenetic transmission across generations via FKBP5 methylation. A persistent tension runs throughout: whether adversity produces fixed deficits or altered regulatory set-points amenable to intervention—a question the intervention literature, from therapeutic foster care to EMDR, addresses directly. The concept is indispensable to any depth-psychological account of psychopathology.