the point where you don't give a fuck anymore and nothing affects you and you just continue living your life; emotionally detached

When your so depressed you dont care about anything anymore and become dead on the inside thus dead inside, its pretty much another way of saying clinical depression

If someone is "dead inside" they have no feelings,emotions or anything of that sort.

It is an adjective (describing word) It can be used as an insult.

Me right now

Dead inside is the state of when one can't be bothered getting out of bed or even turning on their phone

depressed, depression, sad, melancholy, wanting to die, you're dead but inside

A track from Muse's seventh studio album Drones.