Is There a Link Between Vitamin D Deficiency and Depression?

There has been a lot of discussion recently in the scientific world and the lay press about the prevalence and consequences of vitamin D deficiency. As part of that discussion, there has been a suggestion that vitamin D deficiency could contribute to depression and that vitamin D supplementation could be a viable treatment option for depression.  The goal of this e-Weekly is to assess that further.

Observational data over the last 10 years has shown an association between vitamin D deficiency and chronic health concerns, such as depression, cancer and arthritis. What needs to be fully understood is if vitamin D deficiency contributes to depression, or if vitamin D deficiency indicates the presence of depression, or if it is merely a coincidence. If the former has some validity then it makes sense to consider vitamin D supplementation as a treatment for depression.

What is known is that depression is very common in the world population, affecting over 120 million people worldwide. And vitamin D deficiency is even more common in the world population, affecting 1 billion people worldwide. Given that, even though depression treatments are fairly effective, most people with depression either do not seek treatment or discontinue it prematurely because of side effects and other reasons, it thus reasonable and important to search for alternative treatments for this debilitating disorder.

While evidence-based nutritional recommendations for persons with depression and other mental health disorders have not been determined, some small studies are starting to show some positive effects of specific nutritional supplements on some mental health symptoms.

When looking at the relationship between vitamin D deficiency and depression, there are a few things of note. Some studies have shown that the vitamin D levels in people with depression are lower than in people without depression. What is unclear is if there is a causation link or not and where light exposure fits into the equation. When looking at studies on effects of vitamin D supplementation on depressive symptoms, there is some mild positive effect on an anecdotal level but a lack of statistically significant results. It is also important to pay attention to the complicated relationship among vitamin D, sunlight exposure and calcium supplementation, because they all intimately affect each other. And when talking about ancillary treatments for depression, exercise, especially outdoor exercise which leads to additional light exposure and vitamin D exposure, can be an important consideration.

As an additional related side note, there is some evidence from animal studies that vitamin D supplementation could help reduce the risk of new-onset diabetes from antipsychotic use. This is related to the finding that obesity and insulin resistance are inversely related to vitamin D levels. Of course this would need to be studied more before firm recommendations can be made, but it is an interesting finding.  It is also of note that some research findings support the claim that vitamin D supplementation can have an impact in fall reduction and fracture prevention in older adults.

In summary, those groups at risk for vitamin D deficiency include the elderly, adolescents, obese individuals and those with chronic illnesses. Interestingly, these groups are also at higher risk for depression. The role of vitamin D supplementation in treatment for depression has not been fully studied, but if it could have a role as a first line intervention for milder cases, or be used as an adjunctive treatment for those with more severe or treatment resistant depression, or could help with prevention of depression, that would be noteworthy.

In the meantime, recommendations for vitamin D supplementation should be made for patients with the other medical concerns discussed in this article and it could be considered for use as an adjunctive intervention in the prevention or in the treatment of depression.


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