For some people, the changing seasons are welcome. However, for others, the change in seasons can bring about a severe mood change or “wintertime blues” known as Seasonal Affective Disorder (SAD). A recent study review suggests a vitamin D deficiency may be partially to blame.
University of Georgia researchers led an international study that found a link between SAD and a lack of sunlight. Results of the study were published in the journal Medical Hypotheses. Researchers reviewed more than 100 leading articles and found a relationship between vitamin D and seasonal depression.
SAD is believed to affect up to 10 percent of the population, depending upon geographical location. Based on the team’s investigations, vitamin D was likely to be a contributing factor in seasonal depression. They suggest several reasons for this, including the fact that vitamin D levels fluctuate in the body seasonally, in direct relation to seasonally available sunlight.
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. Vitamin D is also involved in the synthesis of serotonin and dopamine within the brain, both chemicals linked to depression, according to the researchers.
Vitamin D levels varied according to the pigmentation of the skin. People with dark skin often record lower levels of vitamin D, according to the researchers. Therefore it is suggested that those with greater skin pigmentation may experience not only higher risks of vitamin D deficiency, but also be at greater risk of developing SAD.
This latest research indicates that maintaining adequate levels of vitamin D are important for good mental health. A few minutes of sunlight exposure each day should be enough for most people to maintain an adequate vitamin D status. During the darker winter season, those who are prone to SAD may benefit from light therapy as well as vitamin D supplementation.