" Paul does not say what precisely had happened, but he tells the Corinthians the effect that it had on him (in a deliberate and completely justifiable plea for personal sympathy): he was so utterly overwhelmed, beyond any capacity to cope, that he despaired of life itself (1:8). He felt as though he had received the sentence of death in himself (1:9). This language—internalizing a death-sentence—sounds close to what we might call a nervous breakdown, and certainly indicates severe depression. "

― N.T. Wright , The Resurrection of the Son of God (Christian Origins and the Question of God, #3)