twenty one pilots – Trapdoor lyrics

The song talks about how depression can eat away at someones sanity. "Cause no body knows his life" is saying that he hides behind a smile and pretends he's ok, but he isn't. "He wakes up early today".
Throws on a mask that will alter his face.
No one knows his real name. " He puts on a mask (a smile) no one knows his real name (they don't know who he actually is, they don't know that he is dying inside).
"take me out, finish this waste of a life " is saying that he wants to die, he thinks his life is a waste in the universe so he's saying kill me now no one will care.
" Watch as this man disappears as we know " is saying that he is slowly getting more and more sadder and slowly getting further and further away from his friends and family.
" Everyone gather around for a show.
Watch as this man disappears as we know. " is saying that his friends and family are just watching him falling down the rabbit whole of depression. They can only watch because he won't let them help him.
" Do me a favour and try to ignore as he fall through a blatant trapdoor" is saying that he feels that no one wants to help him, that everyone is just ignoring him. And he feels that no one can help him so he just tells them he's fine, but he's not.

This song is about depression and a man succumbing to drugs because of how severe his depression is. He throws on his mask of happiness every morning, he puts on a new personality, so no one knows how he feels. He pretends he's okay so no one ever finds out what he's going through. He's petrified at night because 1. he's going crazy due to his depression or 2. he is on a hallucinogen that causes him to see or hear things, and when he takes his last hit at night he sees or hears demons. He wants somebody to kill him because he does not have the strength to do it himself. He wants to die because he is enslaved by his depression and the drug. The chorus is talking about how people see him take the drug for the first time and he changes into a completely different person. Joseph is asking them to ignore that he is doing it voluntarily, he just wants them to try to understand as he throws himself into the pit of addiction. He thinks faith might be dead because he believes that if there was a God or deity he would not have been depressed and turned to drugs, he would not have had to suffer. His own head is killing him with depressing thoughts, his thoughts are all sharp and dangerous. He can't even become peaceful enough in his mind to sleep, which is why he's just watching the backs of his eyes. The last lyric, "Cause nobody knows he's alive," is saying how no one knows there is a man under the influence of the drug fighting his addiction. No one knows there is a man under the facade of happiness fighting severe depression. No one knows that under that skin, inside that head, there is a man battling for his life, and at the moment is losing.

I think this song is really just about a man who never gets what he deserves and everyone ignores him and that he pretends that he is ok and fine but under his feelings he just wants help or death and the verse watch as this man dissapear as we know is saying that anyone could die at any moment and people try to ignore it.