Some scientists have hypothesized that low vitamin D levels may play a role in the development of autism. This most recent study to investigate this possible connection was published in the Jun 2010 Journal of Alternative and Complementary Medicine (J Altern Complement Med. 2010 Jun;16(6):641-5.). This study found that the children with autism had significantly lower vitamin D levels than children without autism. Other studies have found similar results. One study by Dr. Elisbeth Fernell and colleagues (Sweden) looked at the vitamin D levels of Somali mothers who had children now diagnosed with Autism. These mothers had very low levels of vitamin D and their low levels trended lower than mothers with children who did not have autism.
If your child has autism or a related autism-spectrum disorder ask your physician to check vitamin D levels with a 25-Hydroxy-vitamin D blood test, a.k.a 25 (OH) D. Your physician can then determine if additional supplements or sunshine are needed to boost lower than optimal levels. It is not recommended to give high doses of vitamin D to children unless directed by a healthcare professional.
References: www.pubmed.com