Explain why apathy is recognised as a feature of a range of organic and neurological conditions, not only of depressive illness.

Apathy reflects a disturbance in the systems underlying motivation and goal-directed engagement, which can be disrupted by a wide range of processes beyond depressive illness, including various organic and neurological conditions affecting the relevant brain circuitry. Because apathy can occur as part of a depressive illness but is also recognised as a distinct feature of these other conditions, sometimes appearing without the accompanying low mood or distress typically expected in depression, its presence should prompt a broad assessment rather than an automatic assumption of depressive illness. Recognising apathy as its own distinct phenomenon, separable from depressive illness, therefore helps keep the differential diagnosis appropriately wide when a patient presents with pervasive loss of interest and motivation.