What made Oedipus go insane?

Oedipus scratches out his own eyes when he discovers that he has fulfilled the prophesy of the Oracle of Delphi, who told him that he would kill his own father  and marry his mother. Oedipus had not known that the old man he had fought with and killed while on the road to Thebes was his father, Laius, and that he married his mother, Jocasta, unwittingly. Years before, after hearing his prophecy, Oedipus had assumed...

Oedipus scratches out his own eyes when he discovers that he has fulfilled the prophesy of the Oracle of Delphi, who told him that he would kill his own father  and marry his mother. Oedipus had not known that the old man he had fought with and killed while on the road to Thebes was his father, Laius, and that he married his mother, Jocasta, unwittingly. Years before, after hearing his prophecy, Oedipus had assumed that his father and mother were the man and woman who had raised him, when in fact King Polybus and Queen Merope were his adopted parents, who had taken him in from shepherds who discovered him as an infant, after his father had ordered him executed.

Oedipus realizes all of this too late, after his mother and wife, Jocasta, figures  out what has happened and hangs herself in a frenzy of grief and disgust. So what really drives Oedipus to scratch out his own eyes is the confluence of events of Jocasta's suicide, and the realization that he has unwittingly fulfilled the prophecy that he fled his home to avoid. This cruel irony and the revulsion Oedipus feels at knowing that he has been making love to his mother for years, cause him to scratch his eyes out.

Yet I would caution the reader against assuming that Oedipus' reaction means that he "lost his mind." The situation he finds himself in is horrific and extraordinary. Some might argue that Oedipus' incredibly violent and self-destructive reaction to the discovery that he has committed regicide, patricide and incest, is entirely proportional, and not an over-reaction. In the context of a Greek tragedy, this catharsis is not a signal of psychosis, but an epic punishment that fits a truly epic and tragic crime.