A systematic review of clinical trials that have examined the effect of vitamin D supplementation on depression found that the majority of these trials show little to no effect of vitamin D on depression.
Vitamin D deficiency has been implicated in numerous health conditions in recent years, including depressed mood and major depressive disorder.
Recent studies provide some support for an association of vitamin D levels with depression, but the data does not indicate whether vitamin D deficiency causes depression or vice versa.
These studies also do not examine whether vitamin D supplementation improves depression.
The review by Jonathan A Shaffer, an Assistant Professor of Medical Sciences at Columbia University Medical Centre (CUMC) found that only seven trials with a total of nearly 3,200 participants compared the effect of vitamin D supplementation on depression with no vitamin D supplementation.
Nearly all of these trials were characterised by methodological limitations and all but two such trials involved participants without clinically significant depression at the start of the study.
The overall improvement in depression across all trials was small and not clinically meaningful.
"Although tempting, adding vitamin D supplements to remedies for depression appears premature based on the evidence available at this time," Shaffer added.
However, additional analyses of the clinical data by Schaffer hinted that vitamin D supplements may help patients with clinically significant depression, particularly when combined with traditional antidepressant medication.
The review was published in the journal Psychosomatic Medicine.