Systemic Acquired Disorganized Attachment (SADA) is a proposed neurobiological framework describing the functional collapse of Earned Secure attachment in adults. Unlike developmental disorganization originating in infant-caregiver dyadic failure, SADA is driven by the environmental erosion of the adult Endocannabinoid System (ECS) and the dysregulation of Periaqueductal Gray (PAG) inhibitory networks. This paper synthesizes evidence from molecular neuroscience, epigenetics, neuroimmunology, and autonomic physiology to establish SADA as a coherent biological state. We demonstrate how chronic allostatic load depletes anandamide-mediated safety gating, triggers epigenetic silencing of recovery genes (Nr3c1, BDNF, FKBP5), and activates a neuroinflammatory cascade that erodes synaptic architecture. We identify three distinct pathways into SADA — from Earned Secure, Anxious, and Avoidant starting points — and introduce the SADA-Entropy Score, a composite biomarker protocol based on HRV Multiscale Entropy, Cortisol Awakening Response kinetics, sleep architecture integrity, and interoceptive accuracy. The framework redefines attachment relapse as a quantifiable mechanical failure, opening pathways for targeted hardware-first intervention.