One person in the Bible whose behavior fits a schizophrenia diagnosis is Nebuchadnezzar, the king of Babylon. In chapter four of Daniel, the king himself writes an autobiographical account of an extended episode. He was the most powerful ruler in the world, but pride became his downfall. Let’s take a closer look at his mental condition.

Nebuchadnezzar's thoughts were delusional. He declared, “Is not this the great Babylon I have built as the royal residence, by my mighty power and for the glory of my majesty” (4:30)? This bold statement from Nebuchadnezzar is incredible in scope. Babylon was massive and the most powerful empire in the world during its time. The king came to believe he was responsible for that power, wealth, and fame. He held firmly to it, even when the prophet Daniel warned, “Your Majesty, be pleased to accept my advice: Renounce your sins by doing what is right, and your wickedness by being kind to the oppressed. It may be that then your prosperity will continue” (v.27). He was so fixed on these grandiose thoughts that he clung to them despite what came next.

His thoughts became muddled and his thinking disorganized. His mind was "changed from that of a man...[to] the mind of an animal” (Dan.4:16). But his mental faculties were not completely taken from him, because Daniel also informs him “your kingdom will be restored to you when you acknowledge that Heaven rules” (4:26). Essentially, he no longer possessed the mental capacity of a healthy person. Instead, his mind functioned like that of an animal, leading him to walk away from his kingdom and live in the wild. At the end of his account, he informs us that his "sanity" (מַנְדַּע, ability to reason, know, understand) was taken from him (v.34).

During this time, he lacked motivation to perform normal daily activities. “His hair grew like the feathers of an eagle and his nails like the claws of a bird” (4:33). He stopped grooming himself and, we can safely assume, stopped bathing, cleaning his teeth, and cleaning up after relieving himself.

Nebuchadnezzar socially isolated himself. The text makes this a point of emphasis, stating “let him live with the animals among the plants of the earth” (v.15), “let him live with the wild animals” (v.23), and “he was driven away from people” (Daniel 4:33).

It goes without saying, but the king exhibited bizarre behavior, eating grass like the ox" (4:33). Nebuchadnezzar exchanged life as the most powerful man in the world, who regularly dined on delicacies for that of an animal who grazed the wild searching for food. He walked through the wilderness like an animal, with long hair and uncut nails searching for food.

We cannot say for sure that Nebuchadnezzar had an schizophrenic episode (which lasted for seven years, v.16). We can be confident, however, that his behavior matches the symptoms of this disorder pretty closely.