STOCKHOLM, Sweden, July 15 (UPI) -- Two Swedish doctors are calling for more vitamin D amid a possible link between lack of sunlight and an increased rate of autism.

A lack of sunlight during Sweden's winters, combined with the use of sunscreen and efforts to avoid sun exposure can result in vitamin D deficiencies, which some doctors say could contribute to depression and autism, The Local newspaper said Monday.

The problem is especially noticeable in Somalis living in Sweden. Researchers theorize the high incidence of autism in Somali children in Sweden is due to the lower levels of sunlight.

"Dark-skinned people demand significantly more sunlight to enable vitamin D to build up in their skin. The combination of clothing which covers the body and dark skin is a particularly problematic combination, especially for someone who doesn't eat fatty fish," researchers Susanne Bejerot and Mats Humble said in an article published in the Dagens Nyheter newspaper.