A scene where Alicia Nash were told that John has schizophrenia from Dr. Rosen.
After I have finished watching this film, I discovered that it has a singular theme: mental illness and how, in this particular case, John Nash, handles it. John has always been a peculiar person from the start. He recluse himself and didn't talk to others much. The only person that he talks often to is his roommate, which he pours his heart out to.
The mental illness in question is schizophrenia, which the symptoms are social withdrawal, decreased emotional expression, and apathy. Throughout the film, we can see those symptoms on John Nash, starting from excluding himself from socialising with his colleagues, never showing emotion, especially facial emotion towards others, and lacks concern about his other friends, only prioritizing his roommate and only talks to his friends once in a while.
He also experienced delusions, such as seeing a roommate that wasn't there, a secret base for his espionage expedition, seeing numbers and patterns in magazines and newspapers when in fact there were no secret codes at all.
Examples of John's delusions in the film.
In my opinion, these depictions of a schizophrenic patient are true to life. John's schizophrenia can be seen from the start of the film, when he sees patterns that aren't there from a necktie, and eventually his delusions developed into paranoid schizophrenia, where he became suspicious of people because he thought that they were Russian spies.