On the aetiology of autism

I have suggested that the primary environmental trigger for autism is not vaccinations, toxins or infections, but gestational and early childhood vitamin D deficiency (1,2). Subsequently, the title of an article in Scientific American recently asked, ‘What if vitamin D deficiency is a cause of autism? ’ (3) Since then, an article on vitamin D and autism in Acta Paediatrica (4) and the accompanying commentary (5) have added to the accelerating suspicion that vitamin D deficiency – either during pregnancy or early childhood – may be an environmental trigger for the genetic disease of autism. I will not repeat the evidence from my original 2007 paper and I am well aware that evidence consistent with a theory is not proof of that theory. Instead, I concentrate on papers either published since my paper, or on evidence I overlooked when researching the original paper. Finally, I explain my reasons why this theory deserves immediate attempts to disprove it. Simultaneous with the above two Acta Paediatrica publications, a paper elsewhere reported that among 117 adult psychiatric outpatients is Sweden with various diagnoses, the 10 patients with autism had the lowest vitamin D levels of any of the groups studied, a mean of 12 ng ⁄mL (31 nM), approaching the osteomalacic range for adults and the rachitic range for children (6). Even more interesting, some of the patients seemed to improve when treated with an average dose of about 4000 IU of vitamin D ⁄day. The authors did not say if the improvement occurred in the autism group. A 2008 review detailed the devastating effect gestational vitamin D deficiency has on developing mammalian brains (7). Unfortunately, the tiny 10 lg (400 IU) dose in prenatal vitamins is virtually irrelevant in preventing the current epidemic of gestational vitamin D deficiency (8). For this reason, in 2007, the Canadian Paediatric Society cautioned pregnant women they may require not 400 IU ⁄day but 2000 IU ⁄day, or more, to prevent gestational vitamin D deficiency (9). If adequate amounts of vitamin D prevent autism, one would expect children with rickets to have an increased risk of autism. To my knowledge, the neuropsychiatric symptoms of rickets have not been studied in the modern era. However, at least two old papers have addressed it (10,11), both published before Kanner described autism in 1943. Both papers describe ‘weak mindedness,’ ‘feeble minds,’ ‘mental dullness,’ unresponsiveness and developmental delays. Even more intriguing, both papers report that the mental condition in rickets improved with vitamin D. Another of the mysteries of autism is the apparent increased incidence of autism in the children of richer college-educated parents, especially women, a finding announced a few months ago (12). Actually, this is not a new finding. As I discussed in my original paper, this has been known since the early 1980s but was dismissed as being because of ascertainment bias. This very recent report correlates well with a 2007 CDC report (13), which found a similar increased risk for the wealthy and well-educated, Articles in the series A Different View are edited by Alan Leviton (alan.leviton@childrens.harvard.edu). We encourage you to offer your own different view either in response to A Different View you do not fully agree with, or on an unrelated topic. Acta Paediatrica ISSN 0803–5253