In our literature review, we found that some studies have reported associations between peripheral blood metabolites and PPD, but research on CSF metabolites is relatively scarce.[25–27] In our study, some CSF metabolites, such as arachidonate and benzoate, have been mentioned in the context of other psychiatric disorders, but their direct association with PPD has been rarely reported.[28,29] For instance, sodium benzoate, as an inhibitor of D-amino acid oxidase, has been studied in various psychiatric disorders, including schizophrenia and depression. The gene discussed is DAO; the disease is schizophrenia.