COE researchers help link vitamin D, depression

Note: A version of this story appeared in several news outlets, including Science Newsline.

Vitamin D deficiency is not just harmful to physical health, it may also affect mental health, says a team of researchers who have found a link between seasonal depression and a lack of sunlight.

Alan Stewart, associate professor in the Department of Counseling and Human Development Services at the University of Georgia's College of Education, was part of an international partnership with researchers at the University of Pittsburgh and Queensland University of Technology in Australia. The team reported the finding in the November 2014 issue of the health journal Medical Hypotheses.

Stewart and Michael Kimlin from QUT's School of Public Health and Social Work said a review of more than 100 leading articles found a relationship between Vitamin D and seasonal depression.

"Seasonal affective disorder, also known as SAD, is believed to affect up to 10 percent of the population, depending upon geographical location, and is a type of depression related to changes in season," said Stewart, an associate professor in the Department of Counseling and Human Development Services.

"People with SAD have the same symptoms every year, starting in fall and continuing through the winter months."

Stewart said based on the team's investigations, Vitamin D was likely to be a contributing factor in seasonal depression.

"We believe there are several reasons for this, including that Vitamin D levels fluctuate in the body seasonally, in direct relation to seasonally-available sunlight.

"For example, studies show there is a lag of about eight weeks between the peak in intensity of UV (ultraviolet) radiation and the onset of SAD, and this correlates with the time it takes for UV radiation to be processed by the body into Vitamin D," he said. "So rather than being one of many factors, Vitamin D could have a regulative role in the development of SAD."

Vitamin D is also involved in the synthesis of serotonin and dopamine within the brain, which were both chemicals linked to depression, according to the researchers.

"Evidence exists that low levels of dopamine and serotonin are linked to depression therefore it is logical that there may be a relationship between low levels of Vitamin D and depressive symptoms," said Kimlin, a Cancer Council Queensland Professor of Cancer Prevention Research. "Studies have also found depressed patients commonly had lower levels of Vitamin D."

Vitamin D levels varied according to the pigmentation of the skin and people with dark skin often recorded lower levels of Vitamin D, according to the researchers.

"Therefore it is suggested that persons with greater skin pigmentation may experience not only higher risks of Vitamin D deficiency, but also be at greater risk of psychological and psychiatric conditions," he said.

Kimlin, who heads QUT's National Health and Medical Research Council Centre for Research Excellence in Sun and Health, said adequate levels of Vitamin D were essential in maintaining bone health, with deficiency causing osteomalacia in adults and rickets in children. Vitamin D levels of more than 50 nanomoles per liter (nmol/L) are recommended by the United States Institute of Medicine.

"What we know now is that there are strong indications that maintaining adequate levels of Vitamin D are also important for good mental health," said Kimlin. "A few minutes of sunlight exposure each day should be enough for most people to maintain an adequate Vitamin D status."

"Queensland is known as the Sunshine State in Australia but that doesn't mean all Queenslanders get enough Vitamin D," said Kimlin. "This research is of international importance because no matter where you live, low levels Vitamin D can be a health concern."