In the movie, A Beautiful Mind, the main character, Jon Nash is struck with paranoid schizophrenia. His symptoms are primarily positive ones: he exhibits inappropriate behaviors rather than lacking appropriate behaviors. He clearly shows disturbed perceptions including several recurring hallucinations. The most prominent hallucinations include a college roommate for his entire time spent at college, his imaginary roommate's daughter, and a federal agent. Nash frequently seems distracted and appears to have very disorganized and jumpy thought patterns.
The reasons that Jon Nash acquired schizophrenia are not known, but a few theories may apply. Nash seemed to develop schizophrenia at the age most schizophrenics begin to see symptoms: late adolescence. Research suggests that schizophrenia is influenced strongly by genetic factors and then triggered by certain circumstances later in life. Nash may have had a low birth weight or suffered from such birth complications as nutritional and/or oxygen deprivation. He may have encountered prenatal viruses in his mother's womb. Fluid-filled cerebral cavities in his brain may have enlarged to cause the illness.
I think that many possible causes of Nash's illness were revealed in the film. Nash most likely had some genetic predisposition to schizophrenia, along with an excess of dopamine, which was evidenced by the fact that the drugs he received aided his recovery. Nash's path to mental illness probably began young. Nash never has any contact with his parents throughout the film, so there is a high probability that they were distant from his when he was younger. They also did not provide him with a strong relationship throughout the course of the movie. Nash clearly exhibited anti-social tendencies and had a history of social inadequacies. He didn't get along with anyone and he made several enemies at college. Nash lacked the ability to converse with people successfully.
