Moreover, logistic regression analyses including age, sex, smoking status, glutamine, glutamate, glycine, l-serine, d-serine, homocysteine, and NRDC as independent variables revealed significantly lower plasma concentrations of d-serine (partial regression coefficient ± standard deviation: PRC ± SD = 1.875 ± 0.504, p = 0.024) and NRDC (PRC ± SD = 0.143 ± 0.063, p = 0.028), but significantly higher l-serine (PRC ± SD = −0.028 ± 0.013, p = 0.024) and homocysteine (PRC ± SD = −0.195, p = 0.001) levels in patients with schizophrenia compared to those in healthy controls. Here, NRDC is linked to schizophrenia.