I'd like to briefly draw your attention to the review published by Elizabeth DeVilbiss and colleagues  today, covering "what is known about the role of folate in the aetiology of neurodevelopmental disorders."
Folate, is a topic that has graced this blog a few times with autism in mind (see here for example) based on various ideas that folate status during pregnancy might have the ability to modify offspring risk of autism  alongside the idea that autoimmune processes might act on folate receptors in some cases of autism (see here) and what this might subsequently mean for pathology / management. The specific idea that folate levels and folate supplementation during pregnancy might influence autism risk has garnered the most research attention, seemingly also crossing geographies too .
The DeVilbiss review is quite comprehensive in its scope and material covered, summarising "relevant biological, genetic and epigenetic mechanisms" and the various science that has been done so far on this topic. I would certainly agree with their sentiments that "existing evidence is inconclusive" (as previously indicated) in light of the numerous confounding variables also potentially linked to offspring autism risk. That being said, and acknowledging where folate metabolism sits in terms of areas such as MTHFR genetics (see here) and the whole vitamin B12 story (see here) and perhaps beyond (see here), I do think there is more to see in this area and perhaps outside of autism and related neurodevelopmental conditions (see here). Without jumping on the whole epigenetics bandwagon, the link between the folate cycle and DNA methylation in particular (see here) offers a whole slew of research ideas ripe for further investigation.
Music: Lost Frequencies - Are You With Me.
 DeVilbiss EA. et al. Maternal folate status as a risk factor for autism spectrum disorders: a review of existing evidence. Br J Nutr. 2015 Aug 5:1-10.
 Schmidt RJ. et al. Maternal periconceptional folic acid intake and risk of autism spectrum disorders and developmental delay in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study. Am J Clin Nutr. 2012 Jul;96(1):80-9.
 Surén P. et al. Association between maternal use of folic acid supplements and risk of autism spectrum disorders in children. JAMA. 2013 Feb 13;309(6):570-7.
DeVilbiss EA, Gardner RM, Newschaffer CJ, & Lee BK (2015). Maternal folate status as a risk factor for autism spectrum disorders: a review of existing evidence. The British journal of nutrition, 1-10 PMID: 26243379