He began to show signs of extreme paranoia and his wife later described his behavior as becoming increasingly erratic, stating that he began speaking of characters who were putting him in danger. Nash seemed to believe that there was an organization chasing him, in which all men wore "red ties". Nash mailed letters to foreign embassies in Washington, D.C. declaring that he was establishing a world government.
He was involuntarily admitted into the McLean Hospital, April–May 1959, where he was diagnosed with paranoid schizophrenia and mild clinical depression.[3] Upon his release, Nash resigned from MIT, withdrew his pension, and went to Europe, unsuccessfully seeking political asylum in
In 1961 he was involuntarily hospitalized into the
Although prescribed antipsychotic medication, Nash has said he never really took it. For some periods he was forced to or voluntarily complied under the pressure, but after 1970 he was never committed to the hospital again and never took antipsychotic medication again. The film A Beautiful Mind fabricated him later taking the then new atypical antipsychotics, which Nash attributes to the screenwriter (whose mother, he notes, was a psychiatrist) not wanting to incite people with the disorder to stop taking their medication. Others, however, have questioned whether the fabrication obscured a key question as to whether recovery from problems like Nash's can actually be hindered by such drugs and Nash has said they are over-rated and the adverse effects are not given enough consideration once someone is considered mentally ill According to his biographer Nasar, Nash recovered gradually with the passage of time. Encouraged by his then former wife, Alicia, Nash worked in a communitarian setting where his eccentricities were accepted. Alicia also said that for Nash "it's just a question of living a quiet life".
Nash dates the start of what he terms "mental disturbances" to the early months of 1959 when his wife was pregnant. He has described a process of change "from scientific rationality of thinking into the delusional thinking characteristic of persons who are psychiatrically diagnosed as 'schizophrenic' or 'paranoid schizophrenic'" including seeing himself as a messenger or having a special function in some way, and with supporters and opponents and hidden schemers, and a feeling of being persecuted, and looking for signs representing divine revelation. Nash has suggested his delusional thinking was related to his unhappiness, and his striving to feel important and be recognized, and to his characteristic way of thinking such that "I wouldn't have had good scientific ideas if I had thought more normally." He has said that "If I felt completely pressureless I don't think I would have gone in this pattern". He does not see a categorical distinction between terms such as schizophrenia and bipolar disorder. Nash reports that he did not hear voices at first, only some years later around 1964, until later engaging in a process of rejecting them. Nash reports that he was always taken to hospital against his will, and only temporarily renounced his "dream-like delusional hypotheses" after being in hospital long enough to decide to superficially conform and behave normally or experience "enforced rationality". Only gradually on his own did he "intellectually reject" some of the "delusionally influenced" and "politically-oriented" thinking as a waste of effort. However, by 1995 he felt that although he was "thinking rationally again in the style that is characteristic of scientists", he felt more limited.