Research has long shown an association between low folate levels and depression, particularly depression that’s more severe and less responsive to medical treatment. (Folate is a water-soluble B vitamin in its natural form. Folic acid is the synthetic version found in supplements.)
Folate is critical in the development of the human nervous system, so pregnant women must take folic acid supplements. People who abuse alcohol, people with certain illnesses, and those who take a number of different medications are at risk for folate deficiencies, which can present with a variety of cognitive, emotional, and behavioral symptoms. Doctors may check folate levels as part of an initial workup of depression.