Senior author Dr. E. Sherwood Brown, professor of psychiatry at the University of Texas Southwestern Medical Center in Dallas and colleagues at the Cooper Center Longitudinal Study said low levels of vitamin D already are associated with a number of health woes from cardiovascular diseases to neurological ailments.
The researchers examined the results of almost 12,600 study participants from late 2006 to late 2010. Brown and colleagues from the Cooper Institute found higher vitamin D levels were associated with a significantly decreased risk of current depression, particularly among people with a prior history of depression.
The study, published in the Mayo Clinic Proceedings, found low vitamin D levels were associated with depressive symptoms, particularly those with a history of depression, so primary care patients with a history of depression may be an important target for assessing vitamin D levels.
However, the study did not address whether increasing vitamin D levels reduced depressive symptoms, Brown said.
The scientists have not determined the exact relationship -- whether low vitamin D contributes to symptoms of depression, whether depression itself contributes to lower vitamin D levels, or chemically how that happens, Brown said. However, vitamin D may affect neurotransmitters, inflammatory markers and other factors, which could help explain the relationship with depression, Brown said.