Climate Change as a Chronic Stressor: Biological and Psychological Pathways Linking Environmental Change to Human...

Climate-related hazards are associated with adverse mental and physical health outcomes, but exposure-specific human findings are often discussed together with general stress mechanisms without clearly distinguishing their evidentiary strength. This narrative review addresses that gap by examining climate change as a context for recurrent thermal, disaster-related, and psychosocial stress, rather than as a single measurable exposure. Evidence is organized around three interacting biological domains: neuroendocrine regulation, inflammation and oxidative stress, and neuroplasticity. Human observational studies support associations between heat, extreme events, and mental health outcomes; short-term human experiments and animal models provide mechanistic insights but do not establish a chronic biological mediation pathway from climate change to psychiatric illness. Indirect pathways include displacement, livelihood disruption, loss, and anticipatory distress. Air pollution is treated as an interacting exposure with both climate-related and independent determinants. Eco-anxiety, climate anxiety, eco-distress, and ecological grief are distinguished from diagnosable disorders, with clinical relevance assessed through functional impairment and individual context. The review's contribution is an evidence-qualified framework linking exposure timing, biological plausibility, psychosocial appraisal, and unequal adaptive capacity. Practical implications include contextual mental health assessment, continuity of psychiatric care during heat and disasters, and incorporation of psychosocial support into adaptation planning. The proposed framework remains hypothesis-generating and requires prospective testing with repeated exposure, biomarker, and clinical assessments.