Which one of these books has a character with a mental illness that i can write an essay about?

We have to prove that a character has a disease and i need a basic 3 point thesis statement. the books i've read are of mice and men, catcher in the rye, romeo and juilet, a separate peace, and a tale of two cities. An example would be like - Holden Caulfeild has post tramtic stress disorder because he always have flashbacks, gets depressed easily, and always feels tense.