Hi,
I found some research about B12 deficiency and OCD, tho some link homocysteine and vitamin D. What was interesting to me is that there are two case studies (not enough, but interesting) saying that two B12 deficient OCD people recovered completely after supplementing with B12 (I will link the studies if you want).
Two years ago I discovered I was B12 deficient too (110), folate borderline low (can't remember) and vitamin D borderline low (35), with high homocysteine. They discovered I have atrophic gastritis (tho no known cause, but they assume it's autoimmune).
I started supplementing with methylcobalamin which is methylated B12. Initially I felt better, my thoughts would come but also go. But after some time I started feeling nervous after taking it, so I quit. After some pause I switched to hydroxycobalamin which is another active form of B12, but mostly given through injection. Once per month did nothing for me, but switching to once per week felt great, after a month I was a lot better, after two I felt great. My thoughts would again just come but also go, and my homocysteine levels dropped. (Tho better OCD symptoms could be from a lack of stress too). After losing insurance, I had to stop with it, and continue like 8 months after, after two months I felt better, not like before, but we then dropped it to one per two weeks, than one per month, and then problems ocurred. Again I started feeling nervous after taking a shot. I thought I was maybe intolerant to methylcobalamin (as some people are), but it was similar with hidroxycobalamin, so I stopped again.
Recently I saw homocysteine is linked to NMDA receptors, which are targeted in ketamine OCD studies, so that's interesting. It could be that homocysteine levels are actually one to track, but I need further advice on that. Also, during this time I supplemented with D3 vitamin, but nothing crazy, 2000 IU, and sometimes I would miss it.
Have you ever had any B12 or related deficiency and supplemented? If you had I would really like to know. Thank you in advance!