Highlights ■ This paper proposes a contextual and non-reductionist ontology of mental health disorders. ■ It reframes the diathesis-stress model through radical behaviorism and functional contextualism. ■ It emphasizes dynamic interactions between vulnerabilities and environmental stressors. ■ It guides clinical practice toward integrative, personalized, and system-sensitive interventions. ABSTRACT This conceptual article examines the ontological and epistemological foundations of mental health disorders through the lens of the diathesis-stress model. It seeks to articulate how this model contributes to a more comprehensive […]