Here’s a list of studies about vitamin D and autism spectrum disorder:
Distribution of Month of Birth of Individuals with Autism Spectrum Disorder Differs from the General Population in the Netherlands (2017)
Conclusion: This study of 3,478 autistic children in the Netherlands found that children conceived between autumn and winter have a higher risk for developing autism, with conception in October producing the highest risk. The researchers hypothesize that this may be due to lack of sun exposure during the first trimester of pregnancy leading to vitamin D-deficiency. This study also acknowledges that autism rates have been increasing in the Netherlands over the years and this rise has coincided with the medical establishment advising people to avoid sun exposure.
Randomized Controlled Trial of Vitamin D Supplementation in Children with Autism Spectrum Disorder (2016)
Conclusion: In a 4-month, double-blinded, randomized clinical trial involving 109 autistic children from six different autism treatment centers in Assiut City, Egypt, those receiving vitamin D therapy showed significant improvement in their autism symptoms compared to the placebo group.
Vitamin D Status in Autism Spectrum Disorders and the Efficacy of Vitamin D Supplementation in Autistic Children (2016)
Conclusion: In a study of 122 autistic children, 87% had low vitamin D levels (57% deficient, 30% insufficient), with the lowest vitamin D levels found in those with the most severe autism. Of those who underwent vitamin D therapy, 80.72% experienced improvement in their autism symptoms.
Conclusion: In a study of 58 sibling pairs where one child had autism and the other did not, those with autism had lower vitamin D levels compared to their siblings without autism. “The findings suggest that low prenatal vitamin D may act as a risk factor for ASD.”
Conclusion: Individual case study. A 32-month-year-old boy in China demonstrated severe autism symptoms. A blood test revealed that his vitamin D level was an extremely low 12.5 ng/ml. Following two months of high-dose vitamin D therapy, his vitamin D level was raised to 81 ng/ml and he demonstrated significant improvement in his symptoms.
Autism and Vitamin D (2015)
Note: Comprehensive article from the Vitamin D Council.
Conclusion: The vitamin D levels of 40 autistic young adults, along with their siblings, parents, and 40 healthy, age/gender-matched controls were tested. Those with autism had lower vitamin D levels than their siblings, parents, and the healthy matched controls, with 88% of those with autism testing as deficient. This adds support not only to the hypothesis that vitamin D deficiency may play a role in autism development and severity, but that autistic people may also have impaired vitamin D metabolism, potentially contributing to other health problems.
Conclusion: William’s syndrome is thought by many to be the opposite of autism. Unlike autists, people born with william’s syndrome are extremely extroverted, social, outgoing, and friendly. Also unlike autists, rather than having lower vitamin D levels, people with william’s syndrome tend to have naturally elevated activated vitamin D levels and often experience hypercalcemia, the main side effect of vitamin D toxicity. As both autism and william’s syndrome are known for their radical effect on a person’s verbal performance and combined with the facts that autism is known for its association with lower vitamin D levels, william’s syndrome is known for its association with higher activated vitamin D levels, and vitamin D is known to improve verbal fluency, all of this adds support to the hypothesis that autism is, at least partially, a disorder of the vitamin D endocrine system. This is further backed by a multitude of studies proving vitamin D is an effective treatment for reducing the severity of symptoms in autists. Also see: Elevated Plasma 1,25-Dihydroxyvitamin D Concentrations in Infants with Hypercalcemia and an Elfin Facies (1985)
Excerpts: “Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.”
“Vitamin D hormone has been proposed to play a role in autism based primarily on a correlation between autism incidence in populations with low levels of vitamin D.”
“Evidence of increased autism prevalence in regions with lower sun exposure in the general population has been available for some time. In the United States, there is an inverse correlation between autism incidence and exposure to UVB, as measured by the level of ultraviolet (UV) radiation in the child’s state of birth. Children born in overcast and rainy counties of Oregon, Washington, and California are twice as likely to be diagnosed with autism as children born in sunnier parts of these states. Accordingly, there is an inverse correlation between the rapid rise in autism incidence and the percentage of the U.S. population with plasma concentrations of 25(OH)D3 considered sufficient by current guidelines.”
“Autism incidence has also been linked to maternal vitamin D insufficiency in dark-skinned mothers living in northern latitudes. Reports have correlated low concentrations of maternal 25(OH)D3 with increased risk of having a child with behavioral problems associated with autism, such as language impairment and attention-switching difficulties. In addition, Somali mothers who moved to Stockholm have been shown to be severely vitamin D deficient (<20 ng/ml) and have approximately a 4.5 times higher risk of having a child with autism, as compared with native Swedes. This is in contrast to African individuals living in East Africa, who have mean 25(OH)D3 concentrations of 48 ng/ml. Autism incidence in the Somali population living in Minneapolis also appears to be high. In 2008, the Minneapolis school district enrolled 0.94% of Somali children, 0.52% of non-Somali African American children, 0.38% of Hispanic children, and 0.20% of Caucasian children in their citywide ASD preschool program.”
Conclusion: This study of 7,540 autistic children in Los Angeles County, California found that children born from foreign-born black mothers, children born from foreign-born Central/South American mothers, children born from foreign-born Filipino mothers, children born from foreign-born Vietnamese mothers, and children born from U.S.-born Hispanic and black mothers – all demographics with darker skin – have an increased risk for severe autism compared to children from U.S.-born white mothers. Could this be because of the well-documented fact that darker-skinned people are much more likely to suffer from vitamin D-deficiency?
Conclusion: Autism rates are lower in the southern United States, which get more vitamin D-producing UVB solar radiation, compared to the northern United States, which get less UVB.
Reduced Serum Concentrations of 25-Hydroxy Vitamin D in Children with Autism: Relation to Autoimmunity (2012)
Conclusion: Vitamin D levels were measured in 50 autistic children and 30 healthy control children. The autistic children had significantly lower vitamin D levels compared to the healthy controls, with nearly half testing as deficient. There was also a negative correlation between vitamin D levels and disease severity scores on the Childhood Autism Rating Scale (CARS). Children with severe autism had lower vitamin D levels compared to those with mild autism.
Conclusion: A 17-year study of 743 mother-child pairs found that children from mothers with low vitamin D levels during pregnancy went on to have almost double the chance of suffering language difficulties and impairment compared to children born from mother with adequate vitamin D levels during pregnancy.
Conclusion: This study of New Jersey autism rates found that there was a 63% increase in autism diagnoses between 2002 and 2006, a rapid rise in autism prevalence. This adds support to the hypothesis that it could be, in part, due to people increasingly avoiding the sun and using sunscreen out of fear of skin cancer, but unintentionally producing vitamin D-deficiency that may be contributing to autism development. This study also touches on how autism rates are apparently higher in New Jersey compared to other states – adding more support to the autism/vitamin D-deficiency theory, as New Jersey is one of the more northern U.S. states receiving substantially less UVB throughout the year necessary for vitamin D production.
Conclusion: Vitamin D deficiency may play a role in triggering the development of autism during pregnancy, infancy, or early childhood due to vitamin D’s role in immune system regulation, neurodevelopment, and gene regulation.
Conclusion: This study of 3,918 autistic children in Sweden found that children born from Sub-Saharan African migrants, children born from North African migrants, children born from Latin American migrants, children born from Caribbean migrants, and children born from southern Asian migrants all had an increased risk for developing low-functioning autism. Could this be because they are all dark skinned people from extremely sunny areas moving to a country that gets very little sunshine in comparison, putting them and their offspring at an extreme risk of developing vitamin D-deficiency – which could be playing the primary role in the development of their autism?
Reduced Serum Concentrations of 25-Hydroxy Vitamin D in Children with Autism: Relation to Autoimmunity (2012)
Conclusion: This study comparing the vitamin D levels of 50 autistic children and 30 healthy matched controls found that the autistic children had “significantly lower” vitamin D levels. This adds support to the hypothesis that vitamin D deficiency plays a role in autism or that an impaired vitamin D endocrine system is a feature of autism.
Conclusion: Current common pharmaceutical treatments for autism are only partially effective, at best, for improving autism symptoms and carry a number of adverse side effects. Vitamin D on the other hand has been shown to be effective for improving symptoms, without adverse side effects, and is inexpensive.
Conclusion: This study of 6,604,975 children born from 1990 to 2002 in California found that those conceived between December and March had an increased risk of developing autism. These also happen to be the months when population vitamin D levels are the lowest, due to decreased cutaneous vitamin D synthesis during winter when the sunlight is weakest. Could vitamin D-deficiency during the first trimester of pregnancy be the culprit behind autism?
Note: Great article from Psychology Today summarizing the evidence of vitamin D-deficiency increasing the risk of autism.
Socioeconomic Inequality in the Prevalence of Autism Spectrum Disorder: Evidence from a U.S. Cross-Sectional Study (2010)
Conclusion: In this study the Autism and Developmental Disabilities Monitoring Network found that of 3,680 autistic 8-year-olds, the prevalence of autism is roughly double in the higher “socioeconomic” classes – those with higher college educations and higher household incomes. This is in sharp contrast to most other diseases and disorders, which tend to be suffered disproportionately by the lower classes, supposedly due to nutritionally-poor diets and lack of access to superior medical care (might they also be choosing to live unhealthy lifestyles and smoke, drink, do drugs, and watch TV all day?…). Some researchers hypothesize that the increased prevalence of autism among the upper classes may, in part, be due to them making what they consider to be an effort at being more health conscious by intentionally avoiding sun exposure and using sunscreen – which they may be doing for the purpose of avoiding skin cancer, but ignorant of the fact that this will also cause vitamin D deficiency and that vitamin D deficiency has been implicated as at least one factor in autism and many other diseases/disorders. Another possible reason is that upper-class people are far more likely to work indoor jobs for a living, which might have them being completely deprived of sun exposure most days. This is in contrast to the lower classes, who are more likely to work outdoor jobs in fields like landscaping, construction, and agriculture, which has them receiving lots and lots of sun exposure, allowing them to maintain better vitamin D levels. Lower class people are also more likely to have to walk places rather than drive a car, allowing them to receive sun exposure. Less intelligent people may be less likely to think to slather on sunscreen when they go outdoors, allowing for more cutaneous vitamin D synthesis. Lower class people may be much more likely to enjoy outdoor activities like hunting, fishing, camping, hiking, dirt bike riding, and muddin’ – which are not typically associated with wealthy people. Lower class people may also be more likely to wear less clothing when they’re outdoors. For example, lower class men may be more likely to go shirtless throughout the day and lower class women may be much more likely to wear revealing belly shirts, spaghetti strap shirts, bikini tops, and short-shorts during the day. This reduced amount of clothing allows for more cutaneous vitamin D synthesis, as opposed to upper-class people who may be covering up most of their skin in long-sleeve professional attire on a daily basis. Another theory explaining the seemingly higher autism rate in the upper classes is that they may simply be more likely to get their kids examined and treated, whereas autism in the lower classes may go unrecognized and undiagnosed, leading to the false impression that it doesn’t exist.
Conclusion: In this UK investigation into association between the season of birth/conception and autism risk, researchers found that children conceived during summer had a slightly higher risk of autism. Although this contradicts other studies that suggest conception in winter to increase autism risk, this study still adds support to the hypothesis that there may be a seasonal influence on autism development possibly due to the changes in sunlight intensity.
On the Aetiology of Autism (2010)
Note: Overview by Dr. John Cannell on the relationship between vitamin D deficiency and autism.
Note: Article from the Scientific American exploring the evidence linking vitamin D deficiency and autism.
Variation in Season of Birth in Singleton and Multiple Births Concordant for Autism Spectrum Disorders (2008)
Conclusion: This U.S. study of 1,068 autism cases found that children conceived during autumn and winter are at a higher risk of developing autism, adding support to the hypothesis that maternal vitamin D levels during the first trimester of pregnancy may be a critical factor in the development of autism.
Note: Article about the extremely high prevalence of autism among the children of Somali immigrants to Minnesota. Could it be because they are dark-skinned people moving from one of the sunniest areas in the world to an area that gets very weak sunlight, contributing to severe vitamin D deficiency, which may be contributing to the development of autism?
Note: Another article about the extremely high prevalence of autism among the children of Somali immigrants to Minnesota. Could it be because they are dark-skinned people moving from one of the sunniest areas in the world to an area that gets very weak sunlight, contributing to severe vitamin D deficiency, which may be contributing to the development of autism?
Note: And another article about the extremely high prevalence of autism among the children of Somali immigrants to Minnesota. Could it be because they are dark-skinned people moving from one of the sunniest areas of the world to an area that gets very weak sunlight, contributing to severe vitamin D deficiency, which may be contributing to the development of autism?
Conclusion: This cross-sectional study of 75 autistic boys ages 4-8 years old found that they had slightly thinner bones compared to references from the general 4-to-8-year-old male population. As proof of vitamin D-deficiency causing bone weakness and stunting skeletal development is well-documented, the correlation between autism and reduced bone thickness adds support to the hypothesis that vitamin D-deficiency may play a role in the development of autism and that individuals with autism may also suffer from an impaired vitamin D endocrine system, contributing to consistent vitamin D-deficiency and it’s symptoms.
Conclusion: This is another study where researchers found a higher prevalence of autism in the higher socioeconomic classes. Could it be due to their possibly sun-less lifestyle? Indoor jobs, indoor recreation, indoor schooling, top-to-bottom clothing, sunscreen everywhere, and living in a geographic area that receives inadequate UVB?
Prevalence of Autism in a United States Population: The Brick Township, New Jersey, Investigation (2003)
Conclusion: This study found that autism rates have increased since the 1980’s and 1990’s, adding support to the hypothesis that this may be due to the increase in anti-sun propaganda and people increasingly taking the advice of the medical establishment and dermatology mafia to use lots of sunscreen and avoid the sun – leading to vitamin D-deficient pregnant mothers whose fetuses don’t have the amount of vitamin D necessary for proper brain development and vitamin D-deficiency in infancy and early childhood, which may also contribute to autism development.
Conclusion: This study is on how improving autism-detection methods are leading to an increase in autism diagnoses, which may be partially contributing to the perception that autism is “on the rise.” Also, many children who were previously categorized as simply “mentally retarded” are now being categorized as autistic, leading to an increase in autism figures. This theory does not provide a full explanation, however, as it does not, for example, explain why dark-skinned immigrants from equatorial regions begin suffering very high autism rates when the migrate to northern latitudes that are far above the rates for light-skinned natives of those regions and is extremely rare in the migrants’ equatorial home regions.
Conclusion: This 1998 investigation into the autism rate of Brick Township, New Jersey also found the rates had increased since previous investigations.
Conclusion: This study of autism rates in Göteborg, Sweden found that children born from mothers who are Ugandan immigrants to Sweden have a 200x higher risk for autism compared to the general Swedish population. Uganda is literally right on the equator and receives some of the most intense sunlight available on the planet (lots of vitamin D). The sun is so intense that the people there have developed very dark, melanin-rich skin to protect themselves from excess sun exposure. They have more sun than they can handle. Sweden is one of the northernmost territories in the world – rivaled only by Finland, Iceland, Russia, Alaska, and northern Canada. Because of Sweden being so far away from the equator, the country receives very little sunlight compared to Uganda and for months and months out of the year it’s physically impossible to make vitamin D from sunlight. Native Swedes have very light colored skin so they can take full advantage of whatever UVB they do manage to get. It is well-documented that dark-skinned people tend to have lower vitamin D levels than light-skinned people in “developed” countries. In this particular case, you have people with dark-skin living directly at the equator, moving extremely far away north away from the sunny equator in Sweden, where it’s even hard for light-skinned people to get enough vitamin D. If it’s hard for pale native Swede’s to make enough vitamin D, then it’s going to be much, much more difficult, impossible, for dark-skinned people who are used to living at the equator to maintain good health. Indeed, as this study found, their autism rate in Sweden is 200x higher, strongly suggesting that lack of sun exposure is a critical factor in autism development.
Child and Adolescent Psychiatric Presentations of Second-Generation Afro-Caribbeans in Britain (1995)
Conclusion: This study from 1973 to 1989 of second-generation Afro-Caribbean and white children living in a British inner city found that the Afro-Caribbean children had a disproportionately higher rate of autism. Could this be because of the well-documented fact that darker-skinned people are much more likely to suffer from vitamin D-deficiency?
Conclusion: This study of autism cases in Israel found that there is a significant increase in people with autism being born in March and August. A March increase suggest that conception during summer may play a role in autism development. An August increase suggests that conception in Autumn may play a role. Either way, this adds support to the hypothesis that there may be a seasonal influence on autism development involving changes in sunlight intensity.
Conclusion: This study found that autistic children are disproportionately born in March, when most people’s vitamin D levels are lowest following the winter months when it’s either more difficult or completely impossible to make vitamin D from sun exposure.
Autism Causes, Prevention and Treatment: Vitamin D Deficiency and the Explosive Rise of Autism Spectrum Disorder by Dr. John Cannell (Amazon link)