Vitamin D may have a regulative role in seasonal affective disorder (SAD) development, contends a hypothesis from University of Georgia researchers.
The researchers analyzed more than 100 leading research articles to develop their theory, and their findings were published in the November 2014 issue of Medical Hypotheses. They believe vitamin D controls the submechanism associated with SAD symptoms. Lack of sunlight during winter months may contribute to vitamin D deficiencies, they said.
“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,” Alan Stewart, of the University of Georgia College of Education, said in a press release. “For example, studies show there is a lag of about eight weeks between the peak in intensity of 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.”
They also noted the lower vitamin D levels observed in patients with depression compared with patients without the condition. Vitamin D is involved in synthesizing serotonin and dopamine, chemicals linked to depression, in the brain.
“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,” Michael Kimlin, of Queensland University of Technology in Australia, said in a press release.
Vitamin D and vitamin D—responsive elements are particularly concentrated in the hypothalamus, which controls circadian rhythms and neural circuitry, they determined.
Their hypothesis also considered skin pigmentation’s role in vitamin D deficiency and mental health. Coupled with their other findings, the researchers predicted greater risk of vitamin D deficiency, psychological, and psychiatric conditions in darker-skinned patients.
“What we know now is that there are strong indications that maintaining adequate levels of vitamin D are also important for good mental health,” Kimlin said.