Vitamin D — produced by the skin when exposed to sunlight — has been found to be lower in individuals who suffer from seasonal affective disorder, or SAD, in a new analysis of studies spearheaded by the University of Georgia College of Education.
 

"Rather than being one of many factors, vitamin D could have a regulative role in the development of SAD," said researcher Alan Stewart.
 

In a report in the journal Medical Hypotheses, Stewart and colleagues said a review of more than 100 articles and found a relationship between vitamin D deficiency and seasonal depression.

Vitamin D — sometimes nicknamed the “sunshine vitamin” — is also involved in the synthesis of serotonin and dopamine within the brain, both chemicals linked to depression, according to the researchers.
 

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