John Nash, a mathematician, saw patterns in numbers and in events that were not seen initially by others. This lead to his great strides in the field of game theory. In late 1958, his behavior became erratic and he became increasingly paranoid. This was the beginning of his battle with paranoid schizophrenia.
Schizophrenia with paranoia often causes its sufferers to see connections that do not exist. For example, if a man leaves a newspaper on a bench, typically no one would think anything of it, however, someone suffering from schizophrenia might believe it to be some sort of message delivery. The unfortunate aspect of this is that, due to the paranoia, no one can convince the sufferer that what they believe is a pattern or has special meaning is an ordinary event. In Nash's case, although his initial pattern observations were valid, he began to see patterns in newspaper articles and occurrences that did not exist and were really separate, unrelated events.