Insanity is a diseased mind (diseased or disconnected soul) which leads the being to choose to continually inflict destruction and harm to the self and others. If continual destructive abusive behavior is not stopped, it will damage the soul through fragmentation and genetic degradation.
Insanity is a way to define behaviors which create soul destruction, that action which ultimately disconnect the body/mind from the soul. When a being is soul disconnected they experience an unquenchable thirst of desire, black depression, pain and suffering at great levels.
When one is continually destructive to the self, or others, eventually the soul layers fragment and split. When a human being is soul split, they will exhibit tendencies that are called, schizophrenia, dissociative personality, sociopathy (Lack of Empathy), and an array of psychological distortions that lead to insanity. Insanity is a description of the existence of hell realms, and is how to easily recognize possession through satanic (anti-life) behaviors that are controlled by the possessing entity.