Hsieh YC, et al. - Via performing this systematic review and meta-analysis, researchers examined the effect of folate in bipolar disorder (BD) patients. Searching the PubMed, Embase, ScienceDirect, ClinicalKey, Cochrane Library, ProQuest, Web of Science, and ClinicalTrials.gov databases until December 21st, 2018, they included six articles involving 481 patients with BD and 760 controls. Outcomes revealed significantly lower serum folate levels in the patients with BD vs those observed in the controls. This indicates a possible effect of lower serum folate levels in a patient with BD. However, the potentially confounding effects of mood states on the folate levels could not be distinguished.