Ok, I know this may sound a bit out of left field, but the OCD/anxiety thing makes me think about BH4. Genetic inability to synthesise BH4,, interferes with B12 transport & messes with dopamine and serotonin. Low serotonin, cos of low Bh4, leads to loss of gut motility etc.
Stress depletes BH4 massively from what I read.
Researchers are talking about BH4 in relation to bipolar and schizophrenia but perhaps milder BH4 deficiency results in anxiety and OCD?
I notice Dr Amy Yasko is all about lithium these days...and there is a relationship between lithium and BH4. I'm not sure but I think lithium up regulates BH4 genes?
It would be interesting to know who has got snps in bh4 synthesising and processing genes on their 23andme panels.