Aboulia is a term in neurology to describe a lack of will or initiative. It lies on a spectrum of symptoms ranging from apathy (which is less severe) and akinetic mutism (which is more severe). It is characterized by an inability to either take action or make decisions without assistance. It was originally thought to be a form of mental illness, but since has been identified as a symptom of many illnesses, both mental and organic.
Athough it's exact mechanism is unknown, Aboulia is a well established symptom of several diseases. A differential diagnosis should include clinical depression, schizophrenia, Parkinson's disease, Huntington's disease, brain trauma and stroke.