(1) Acedia is a term of the classical greek vocabulary that a christian author of the IVth century, Evagre the Pontic, uses in a special sense, to describe a mental state characterized among other things, by disgust and dejection, and which, according to him, falls into what became the first list of deadly sins.
(2) One century later, Pope Gregory the great removes acedia from the list of deadly sins, either because he does not distinguish it from sadness (and laziness) or because he considers it a morbid state and, as such, depending on medical care.