A recent review of apathy proposes an integrative (holistic) model for understanding the condition, in common with other forms of BPSD.
“As with other BPSD, …neural mechanisms alone do not completely account for the syndrome – individual, caregiver and environmental factors also contribute to apathy”.
Massimo, L. Kales, HC. [and] Kolanowski, A. (2018). State of the science: apathy as a model for investigating behavioral and psychological symptoms in dementia. Journal of the American Geriatrics Society. April 2018; Vol.66, Supplement 1: S4-S12.