We previously discussed how toxic components such as mercury could be entered into our 6th Generation model of medical science. In that case, mercury is considered as an additional non-independent variable on the input to the model. Now, we want to extend the same model to neuro-development, a process that is known to be very dependent upon epigenetics, that is, gene regulation by DNA promoter methylation.
If DNA methylation capacity is limited by reduced function of the single carbon metabolism cycle ( production of glutathione, SAM ) then consequently, neuro-development will be impacted.
Identification of methylation deficiency in impaired children
It has previously been recognized that impairment at the single carbon metabolism level is a significant factor in autism . A nutritional supplement targeting methylation deficiency was successful in returning the system to it's normal range of function.
This metabolic profile is consistent with impaired capacity for methylation (significantly lower ratio of SAM to SAH) and increased oxidative stress (significantly lower redox ratio of reduced glutathione to oxidized glutathione) in children with autism. The intervention trial was effective in normalizing the metabolic imbalance in the autistic children.James (2004) 
This study was successful in returning glutathione and SAM to normal ranges, but what is not clear from this study, or further studies by this group, is whether the neurological symptoms are reversible.
Education is the study of cognitive ability. Educators are really more interested in the bottom line than with blood levels of chemical intermediaries. For the final chapter of this post, we have to go to China, particularly the Harbin Medical University in Harbin China. A group led by Sun et. al.  tested related dietary supplements and their effect on in-class performance of afflicted students.
The results illustrated folic acid intervention improved autism symptoms towards sociability, cognitive verbal/preverbal, receptive language, and affective expression and communication. Furthermore, this treatment also improved the concentrations of folic acid, homocysteine, and normalized glutathione redox metabolism. Folic acid supplementation may have a certain role in the treatment of children with autism.Sun (2016) 
ConclusionMany types of autism are due to failures at the level of glutathione and SAM production. These processes may be dependent upon multiple interacting ( non-independent ) factors that include nutrient availability and toxic load. It has been shown that nutrition supplements can:
- Restore function of single carbon metabolism cycle
- improve neurologic performance as measured in a structured teaching mode
 S Jill James, Paul Cutler, Stepan Melnyk, Stefanie Jernigan, Laurette Janak, David W Gaylor, and James A Neubrander Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism1,2 [Full Text]
 Sun C, Zou M, Zhao D, Xia W, Wu L. Efficacy of Folic Acid Supplementation in Autistic Children Participating in Structured Teaching: An Open-Label Trial. Nutrients. 2016 Jun 7;8(6). pii: E337. [PubMed]