NRDC and schizophrenia: Many correlations between various factors found in control participants (between homocysteine and sex, glutamine, and glycine; glutamine and l-serine; glycine and l-serine; and NRDC and l-serine) were not found in patients with schizophrenia, although significant correlations between d-serine level and age, as well as between d-serine and glutamate levels, were found.