What is Holden's obsession about sickness?

doesn't
want us to think that he's been admitted to a psychiatric hospital purely on account of his
mental health issues. By telling us how he often gets sick, he's trying to convince us that his
admission to a mental health facility is because of a general breakdown in his health, which
just happens to include his mental health.

There are good reasons why Holden
should be so keen to minimize his mental health problems. At the time when
is set, there was still a great stigma attached to mental illness. It's striking that even a
stubborn non-conformist like Holden, someone with such a profound contempt for social
convention, should be so anxious to avoid being tarred with the "mad"
brush.