I’ve come across two published studies which are concerning, but they give some clues and science into the causes and development of Autism conditions (and likely also ADHD).

Both studies looked into the levels of vitamin B12 and folate, being two of the main B-vitamins, in both pregnant women and newborn babies, and the relationship to the development of Autism.

One study (Raghavan et. al., 2018) investigated 1257 mother-child pairs to find out the mother’s multivitamin intake during the pregnancy, and testing blood levels of vitamin B12 and folate in the mother and baby 2-3 days after birth. Approximately 86-90% of women in the study were taking multivitamin supplements. This study found that even low to moderate intake of multivitamin supplementation was associated with an increased risk of Autism development. High blood levels of folate was found to have a 250% increased risk of ASD development. Similarly, very high vitamin B12 levels was also found to be associated with a similar level of ASD development. The highest risk of development of Autism conditions were in mothers who had elevated levels of folate AND vitamin B12.

A second study (Raghavan et. al., 2020) confirmed the previous study’s findings that mothers with high folate levels had a 200% risk of development of Autism and/or ADHD in their babies, but when combined with similarly high vitamin B12 levels, the risk of Autism/ADHD development jumped dramatically to 1,760% compared to mothers with optimal folate and B12 levels. This was confirmed when the baby’s cord blood were analysed, showing when there were high unmetabolised folic acid levels, there was a 200% increase of Autism risk, or 1000% increase in African-American babies. The authors ruled out that the high folate levels were not from natural folate from plant foods, but only from folic acid in supplements and/or fortified or processed foods.

How is this possible, when vitamin B12 and especially folate (as folic acid) are highly recommended and even prescribed by doctors to prevent neural tube defects in babies?

There are a number of reasons for these findings. The main issue is that while vitamin B12 and folate are absolutely essential vitamins for DNA replication, and the growth and development of the foetus and babies, there’s a huge difference between these vitamins in foods vs. in supplements. And some folic acid products being prescribed by doctors contain 10-20 times the normal dose of folate! This can be far too much and exceeds the body’s ability to metabolise the folate and B12, to cause very high and toxic levels of folic acid in the mother’s body (and likely in the foetus too).

Pregnant women, or those trying to conceive, are usually recommended to take a high dose folic acid supplement, either on its own or in a pregnancy multivitamin. But folic acid is not folate!

Folic acid is a completely different and synthetic form of folate, which isn’t found in foods. It’s found in fortified wheat flour by law, and hence in breads and bakery products, processed foods, pasta, and more foods, and often in cheap over the counter multivitamin supplements. Folic acid isn’t metabolised in the same way in your body as natural folate from foods, and is a much slower process. Regular or high doses of folic acid can then build up in the mother and foetus/baby to high levels. This can cause an issue called “Unmetabolised Folic Acid Syndrome”, which can cause a number of symptoms including mental health issues.

Other studies have found that folic acid can actually BLOCK the folate receptors on cell walls, to further slow down the metabolism of natural folate from foods. But because metabolism of folic acid is slower and further exacerbated by folic acid blocking the use of natural folate, the high levels of folate when blood is tested, is actually a functional deficiency of folate! Having a deficiency of folate, even with supplementing and especially from folic acid, can then CAUSE neural tube defects and Autism conditions.

If the mother or baby has any of the MTHFR genetic variants, this can reduce the metabolism of folate even more, to cause higher levels of unmetabolized folic acid which can further contribute to a functional deficiency of folate (and B12) and increase the development of Autism and ADHD conditions.
Similarly to folic acid, there are poorly bioavailable synthetic forms of vitamin B12, especially of cyanocobalamin, which as its name suggests is a cyanide form of vitamin B12, where cyanide is a byproduct of the body’s metabolism of this form of B12. Again it’s a slower metabolic process than natural B12 from animal based foods. Cyanocobalamin is used in cheap retail multivitamin supplements, and should be avoided as should folic acid.

Having functional deficiencies of folate and/or vitamin B12 causes reduced methylation functions in the body, which can increase levels of homocysteine, a toxic metabolic byproduct, which can cause high levels of oxidative damage in the body. The brain and nerves are the most sensitive parts of the body to oxidative damage, which can affect moods, behaviours and mental health. Hence this is another mechanism for folate and B12 deficiencies contributing to the development of ASD conditions.

What’s the solution then?

There are a number of things which can be done to reduce the risks of Autism/ASD/ADHD conditions, but the first is the avoid intake of folic acid in supplements, fortified and processed foods, and avoid the cyanocobalamin form of vitamin B12 too. There are other better and safer forms of these B-vitamins, if supplementation is needed or if dietary intake is inadequate or if the digestive system needs support.
As per other articles I’ve written on Autism, ASD conditions and ADHD, having a folate and/or vitamin B12 deficiency isn’t the only cause or factor in the development of these conditions. But these deficiencies ARE a very common cause in ASD conditions, in my clinical experience. It would be very rare for a child, teen or adult with Autism or ASD conditions or ADHD to not be deficient in folate and/or vitamin B12 in their diet, or blood test results showing them as not being deficient in these important B-vitamins, or having very high levels which suggests that their use is being blocked to cause the same symptoms as a deficiency.

If someone has Autism or ADHD, the information and findings from these studies suggests that the incidences of Autism conditions could be reduced and prevented with better forms of these essential B-vitamins, especially in pre-conception or during, or even that symptoms in those with Autism/ADHD conditions could be reduced to improve their mental health and quality of life!

These studies show the importance of getting tested for B-vitamin status prior to trying to conceive and get pregnant, as well as during the pregnancy, and getting good nutritional advice from experts (ie, NOT from doctors), and using better forms of the B-vitamins or pregnancy supplements during these times.
Stay healthy!

References:

Raghavan, R., Riley, A. W., Volk, H., Caruso, D., Hironaka, L., Sices, L., Hong, X., Wang, G., Ji, Y., Brucato, M., Wahl, A., Stivers, T., Pearson, C., Zuckerman, B., Stuart, E. A., Landa, R., Fallin, M. D., & Wang, X. (2018). Maternal Multivitamin Intake, Plasma Folate and Vitamin B12 Levels and Autism Spectrum Disorder Risk in Offspring. Paediatric and perinatal epidemiology, 32(1), 100–111. DOI: 10.1111/ppe.12414

​Raghavan, R., Selhub, J., Paul, L., Ji, Y., Wang, G., Hong, X., Zuckerman, B., Fallin, M. D., & Wang, X. (2020). A prospective birth cohort study on cord blood folate subtypes and risk of autism spectrum disorder. The American journal of clinical nutrition, 112(5), 1304–1317. DOI: 10.1093/ajcn/nqaa208

A scientist in the USA has proposed a new model or theory on the development and progression of Autism in a recent published study.
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While autism has been studied for a century, no single cause to autism has been found. The operative word here is “single”, as almost all published studies and research into Autism and related conditions, including ADHD, are only trying to find if ONE factor is a cause to Autism. But the studies almost always don’t find that one link is a cause in the majority of people, then the studies conclude that the one factor isn’t related to Autism, and this becomes a public belief. And that possible cause becomes forgotten.

As a result, Autism is believed by many to just be genetic, as a default fallback explanation, as there seems to be no other proven reason.

But like other symptoms and conditions or diagnoses, there is always more than one root cause or factor in contributing to the development and progression of health conditions. But it is very difficult to prove using scientific principles in published studies that more than one factor, or a combination of factors, are the causes of something like autism.

In this very recent (January 2026) new study, the author suggests that there’s a 3-stage or a “3-hit” model for the development of autism in children (Naviaux, 2025), being:

1. A genetic predisposition – as while there are hundreds of genes linked to Autism, not all children who have these genes will actually develop Autism. Hence it’s not just genetic. These genetic traits make them more susceptible and sensitive to environmental triggers, including a hypersensitivity to stress.
2. Environmental triggers – environmental factors are known to cause health issues and to also trigger genetic issues through the concept of epigenetics. Such environmental factors include pollution and toxicity, metabolic issues and other stressors.
3. Chronic exposure and hypersensitivity to stresses and other environmental factors, including toxicities, which diverts a child’s necessary brain development instead toward having to deal with the chronic stresses and other environmental toxicities.

One of the claims in this study is that up to half of autism/ADHD cases can be reduced or even prevented from supporting the mother prior to and during pregnancy, and supporting the baby in early childhood. The author of the study says “Autism is not the inevitable result of any one gene or exposure, but the outcome of a series of biological interactions, many of which can be modified”.

It might be controversial to some people that autism/ADHD can be prevented, but if we do know what the environmental triggers or toxicities are, we can reduce exposure or even eliminate those triggers, which can in turn reduce or prevent the autism/ADHD symptoms! And we DO know what those environmental triggers and toxicities are! That’s what I look for in my consultations and investigations in children or adults with autism/ADHD.

For more information on how I can help with Autism conditions or ADHD, please check out the rest of my website or use the Bookings link to book a consultation!

Stay healthy!
 
References:
Naviaux, R.K. (2026). A 3-hit metabolic signaling model for the core symptoms of autism spectrum disorder. Mitochondrion, 87:102096. DOI: 10.1016/j.mito.2025.102096