Older people with lower vitamin D levels are at a greater risk for depression, according to a new study.

The web site AgeConcern.com reported Thursday that research published in Science Daily found that vitamin D deficiency triggers higher blood levels of parathyroid hormone, which is believed to cause depression. According to the web site, 13 percent of senior citizens over 65 are depressed.

The new study, conducted by a research team in Amsterdam, studied 1,282 seniors aged 65-95. According to AgeConcern.com, “169 had a minor depressive illness and 26 were majorly depressed. Those with depression were found to have 14 per cent lesser vitamin D in their blood levels. Over half of the women and 38.8 per cent of the men studied had insufficient vitamin D levels.”

The research team told AgeConcern.com that “Decreased vitamin intake may be secondary to depression, but depression may also be the consequence of poor vitamin D status.”

Vitamin D is made naturally when humans are exposed to UVB in sunlight. Science has also linked UVB exposure to endorphin production in the body – another mechanism by which sunlight is linked to good mental health.

“Decreased outdoor activity and different housing or clothing habits were all believed to decrease vitamin D,” AgeConcern.com wrote. “However, a healthy dose of sun exposure can relieve minor feelings of depression.”