BDNF and major depressive disorder: In terms of predictive ability, serum BDNF demonstrated higher accuracy for the diagnosis of epilepsy [area under the curve, AUC = 0.701, 95% confidence intervals (95% CI) 0.601 ~ 0.801], while serum 5-HT was the best marker for predicting the development of depression in epilepsy patients (AUC = 0.727, 95% CI 0.632 ~ 0.821).