Historically, medicine and clinical practice were dominated by the Biomedical Model, formulated on Descartes' mind-body dualism, which posited that all diseases and physical disorders can be explained by specific biological disturbances, such as pathogens, genetic defects, or biochemical imbalances. While highly successful in infectious disease control, the biomedical model failed to account for chronic illnesses, pain disorders, and why individuals exposed to identical pathogens exhibit vastly divergent clinical outcomes.
In response, American psychiatrist George L. Engel formally introduced the Bio-Psycho-Social (BPS) Model in 1977 in Science. Engel argued that health and illness are systemic outcomes resulting from the continuous, reciprocal interaction among three distinct yet overlapping domains:
- Biological Dimension: Encompasses anatomy, physiology, genetic predispositions, neurochemistry, immune function, and pathogen vulnerability.
- Psychological Dimension: Involves cognitive appraisals, emotional regulation, personality traits, coping mechanisms, beliefs about health, and behavioral responses.
- Social Dimension: Consists of socioeconomic status (SES), interpersonal relationships, cultural norms, institutional support, environmental stressors, and access to healthcare systems.
Theoretical underpinnings also draw heavily from Selye's General Adaptation Syndrome (GAS) (1936), Lazarus and Folkman's Transactional Model of Stress and Coping (1984), and Bandura's Social Cognitive Theory, all of which emphasize that cognitive mediation and environmental feedback loop directly into physiological reactivity via the Hypothalamic-Pituitary-Adrenal (HPA) axis and sympathetic-adrenal-medullary (SAM) system.