Why does Holden Caulfield want to move west in The Catcher in the Rye?

When Holden says he wants to move west, he is not actually meaning that he will move west. Metaphorically speaking, he wants to move west were he can be mute and deaf, but it actually means that he wants to commit suicide. He doesnt commit suicide because when he sees that his little sister wants to go with him west, he is afraid that since he is depressed of Allie's death, that his little sister will kill herself after Holden kills himself.