The biopsychosocial model is not a polite 'all of the above' answer. It's a serious claim: no psychological disorder yields to a purely biological, purely psychological, or purely social explanation.
Depression illustrates it cleanly. Genetic vulnerability (biological) plus negative cognitive style (psychological) plus chronic stressors like poverty or social isolation (social) produce the syndrome together. Treating only one layer — medication without therapy, therapy without addressing housing insecurity, etc. — routinely underperforms integrated care.


