What is genuine, unending insanity?

Obviously there is no definitive to my question I know that but I'm looking for the closest thing. What I've been able to gather is that "insanity" is usually medically referred to as psychosis. And that insanity can come from a line of different disorders; Schizophrenia, Schizoaffective, Bipolar, Dementia, Delusion Disorder, substance abuse.

Anyways, the question I'm trying to ask is what disorder, or chain of events leads to "insanity". Not something that can be fixed by a pill, rather the stories you hear about that old lady that lives in your town that were social butterflies in their youth and at some point they lost something and with that loss they lost themselves. They stopped showing up to town meetings, their facebook page would be filled with posts of nonsensical rambling spanning from minutes apart to eventually none at all. Maybe you drive by her house and you see her—hair matted, barefoot in a night gown simply wandering the yard muttering something to herself.

Or like a story I saw on here: A guy born into immense wealth, witty, quick to a joke. One day he's seen sleeping outside of his own mansion. He wanders the town barefoot, looking like a beggar but doesn't ask for a dime. He takes a lap around his neighborhood until he finds his way back to that patch of grass day in and day out until he went missing and was later found dead.

Though both of these events could've most likely been prevented through medication, what about those people rotting in the psych ward. They take all the medications, go through ECT, every form of therapy possible and they're still as they were when they came in.

What is genuine, never-ending, insanity?