Can Vitamin D Cure Depression?

The ever-popular vitamin D is the “sunshine vitamin”,[1] and sunshine is implicated in mood. So it makes sense that researchers have intently explored vitamin D supplementation for depression — supplemental vitamin D is relatively inexpensive and safe, and may provide a variety of health benefits beside brightening your mood.

But depression is complex. There are many possible causes, and no magic bullet. While you may not expect vitamin D to be a magic bullet per se, you may want to understand the current state of the evidence: what do trial results show, and how exactly exactly does vitamin D impact mood-related pathways?

What does the evidence say?

Two reviews of observational studies and intervention trials reached the same conclusions: When parsing the observational data, both reviews found a correlation between depression and low levels of vitamin D (≤20 ng/mL). When parsing the trial data, both reviews found benefit from supplementation but also low methodological quality and high risk of bias.[2][3]

Those two reviews were published in 2017 and 2016, so shortly after a 2015 meta-analysis of RCTs reported finding no significant reduction in depression after vitamin D supplementation. Its authors, however, mentioned that “most of the studies focused on individuals with low levels of depression and sufficient serum vitamin D at baseline”.[4] In other words, they didn’t rule out the possibility that in people with higher levels of depression or lower levels of vitamin D, supplementation might be more effective.

This hypothesis lines up with the conclusions of a 2014 meta-analysis, which found that, if one considered only the studies whose subjects had low levels of vitamin D at baseline (≤20 ng/mL) and were then given enough vitamin D to achieve sufficiency over the course of the trial, then supplemental vitamin D was about as effective as antidepressant medication.[5] However, this meta-analysis did not account for publication bias.