Social determinants of health are frequently represented as sets of exposures associated with disease, healthcare use, or mortality. Although useful for surveillance and risk stratification, this representation can obscure the processes through which social conditions become consequential for health. This Critical Review examines social determinants as components of interconnected material, psychosocial, relational, behavioral, healthcare, institutional, and temporal mechanisms rather than as independent risk factors. Evidence is interpreted with explicit separation between observed association, mechanism-compatible findings, causal inference, and the synthesis proposed by this review. Material resources alter feasible opportunities as well as perceived scarcity; chronic threat may become biologically embedded but does not operate through a uniform biomarker pathway; social relationships can buffer adversity while coexisting with structural disadvantage; institutions distribute resources, constraints, and power; and behavior can function simultaneously as mediator, adaptation, and outcome. Healthcare systems further modify how social conditions translate into access, treatment trajectories, and clinical consequences. The review argues that meaningful explanation requires attention to scale, timing, feedback, competing mechanisms, and unequal capacity to exercise agency. This mechanistic reframing provides a basis for more discriminating intervention design, measurement, and causal research without treating the proposed framework as a validated universal model.
