I read in most reviews of The Catcher in the Rye that Holden is in a mental hospital. But where can I find that in the book? Isn't he just in the hospital for checkups?
According to this passage, he's in a normal hospital:
“I have no wind, if you want to know the truth. I'm quite a heavy smoker, for one thing--that is, I used to be. They made me cut it out. Another thing, I grew six and a half inches last year. That's also how I practically got t.b. and came out here for all these goddamn checkups and stuff. I'm pretty healthy, though.” [I]
Salinger frames Catcher in the Rye by having Holden begin his tale of all this "madman stuff" that happened from "this crumby place" not too far from Hollywood in Chapter One. Then in the final chapter, Salinger brings the reader back to the present day Holden who is recuperating from his ordeal over Christmas.
Now Holden never explicitly says, 'Hey, my parents checked me into a mental hospital,' because let's face it--he has never been a very straight-forward narrator, or a reliable one. As with everything else Holden says, you have to read between the lines and use your best judgment to determine what is really going on. The clues in the text, along with what Holden says, point to the fact that he is definitely in a hospital or some kind of sanitarium. Consider this passage from chapter twenty-six:
"That's all I'm going to tell about. I could probably tell you what I did after I went home, and how I got sick and all, and what school I'm supposed to go to next fall, after I get out of here, but I don't feel like it. I really don't. That stuff doesn't interest me too much right now.
A lot of people, especially this one psychoanalyst guy they have here, keeps asking me if I'm going to apply myself when I go back to school next September."
From Holden's perspective, the reader knows that he has been "sick," and earlier he mentions having to "rest up." The fact that Holden has been having regular visits from a psychoanalyst suggests that Holden might be on the receiving end of some psychiatric care, regardless of whether he is in a regular hospital, sanitarium, or a mental hospital. Since the reader knows that he has been an extended care patient for quite some time, it seems likely that Holden is 'resting up' at a special facility; Not to mention that his parents are very wealthy, they could afford to put Holden in the best possible place to help him recover.