With a physical injury you can see the damage and pain. You cry out for help and they fix you back up with a cast and such.
With a mental injury you can’t see the damage and pain. You cry out for help and no one can see invisible illness. They don’t fix you, they feed you pills and send you on your way.
Then you get so lost in your pain and sickness you become self-absorbed helplessly, you don’t want to, you just can’t help it. Your brain is damaged and you are crying out for help just like with a broken leg. Yet, no one can see it.