The ontology of mental health disorders: embracing the diathesis-stress model

■ 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.