Hippocampal Neurosustainability for Stress Resilience: A Pro-Neurogenic BDNF-Targeted Architectural Enrichment Framework to Overcome Type 2 Allostatic Overload.

Chronic stress is among the most pervasive health challenges of contemporary urban life, yet its persistence is not simply a matter of external pressure. When adult hippocampal neurogenesis is impaired, the brain loses its capacity to regulate the hypothalamic-pituitary-adrenal (HPA) axis and distinguish new threats from familiar ones through dentate gyrus pattern separation, rendering stress self-perpetuating. Physical activity is widely recognised as a promoter of neurogenesis through brain-derived neurotrophic factor (BDNF), yet the built environments in which most people spend approximately 90% of their time simultaneously suppress BDNF through chronic stress and deny sufficient physical activity intensity to restore it, a condition known as type 2 allostatic overload sustained by architectural impoverishment. This paper proposes architectural enrichment as a theoretical framework designed to resolve this problem at its root through two independent but synergistic mechanisms: architecturally mediated voluntary stair use to elevate peripheral BDNF via metabolic pathways, and neurobiophilic design based on the Neurobiophilia Index to attenuate cortisol and passively support BDNF and neurogenesis. Twelve hypothesised neurobiological profiles are derived in a framework that advances the concept of hippocampal neurosustainability, proposing that buildings can be designed not merely to avoid harming the brain but to actively sustain its capacity for resilience amid the stressors of modern urban living.