In the movie A Beautiful Mind at what point did John Nash start to display schizophrenia?

In the movie "A Beautiful Mind," John Nash begins to display symptoms of schizophrenia during his time at Princeton University, particularly after he becomes increasingly consumed by his obsession with finding a groundbreaking mathematical theory. His hallucinations and delusions become more pronounced when he starts to interact with imaginary characters, like his roommate Charles and government agent Parcher. These manifestations escalate as the film progresses, culminating in a significant breakdown that leads to his eventual diagnosis.