Here are some links relating to folic acid(folate), SAMe, B12, methylation (betaine, TMG)levels and the methylation cycle. This affects depression and dementia and or perhaps a early precursor of some form of dementia:- a "fuzzy" (non clear) thinking. I would expect this to occur in the more mature age in particular as absorption of folate or B12 may sometimes be non optimal in older age (and this could be from middle age with a gradual decrease leading to a gradual decline). A lowish, albeit still in normal range folic acid level, may lead to "fuzzy" (non clear) thinking.
One of my friends on here has found folic acid has helped him.
Folate Cycle and the associated Methylation Cycle:
See page 5;
http://www.metafolin.com/pdfs/Scientific_Review_13.12.pdf
See Figure 1; (enlarged clear figure below)
http://jn.nutrition.org/cgi/content/full/136/10/2653
Figure 1 (above) enlarged;
http://jn.nutrition.org/content/vol136/issue10/images/large/2653fig1.jpeg
Better diagrams of Stahl's than those he has on the Deplin website. See Figure 2 and Figure 5;
http://www.cnsspectrums.com/aspx/articledetail.aspx?articleid=1267
An article from 2006 entitled "New and Emerging Treatment Options for Neuropathic Pain".
Treatment of diabetic peripheral neuropathy (DPN) using a combination of L-methylfolate, P-5-P, and B12. See paragraph 10, not counting the abstract.
http://www.ajmc.com/Article.cfm?Menu=1&ID=3156