Study: Link Between Low Vitamin D, Depression

Researchers estimate that 13 percent of all people older than 65 are depressed, and a new study suggests that those who have low levels of vitamin D may be at a higher risk of depression. The new research, which is published in the May issue of Archives of General Psychiatry, showed that those who are deficient in vitamin D have high levels of parathyroid hormone, which has been linked to depression.

Dutch scientists measured the blood levels of vitamin D and parathyroid hormones in 1,282 study participants between the ages of 65 and 95.

They found that 26 participants were suffering from a major depressive disorder, 169 had minor depression and 1,087 did not suffer from depression.

The study found that 38.8 percent of men and 56.9 percent of women had insufficient vitamin D levels.

In those people who had both major and minor depression, vitamin D levels were 14 percent lower than in people who did not suffer from depression. Parathyroid hormone levels were five percent higher in those people who fell into the minor-depression category, and 33 percent higher in those who were severely depressed, compared with those who had no depressive symptoms.

Despite the findings, researchers aren't sure whether the depression leads to the reduced vitamin D levels and elevated parathyroid hormone or vice-versa. However, researchers say the good news is that low vitamin D levels in the blood and elevated parathyroid hormone levels can be easily modified through an increased intake of vitamin D and more sun exposure.

"Underlying causes of vitamin D deficiency—such as less sun exposure as a result of decreased outdoor activity, different housing or clothing habits and decreased vitamin intake—may be secondary to depression, but depression may also be the consequence of poor vitamin D status," the authors write.

Researchers suggest more studies be undertaken to determine this relationship.