A reader recently sent in a comment wondering about the possible role of vitamin B12 supplementation in psychiatry.
Here's a brief review of the literature:
http://www.ncbi.nlm.nih.gov/pubmed/21191533 --a small case report of b12-deficient individuals responding better to antidepressants after b12 supplementation.
--survivors of stroke who took folic acid 2mg/d, b6 25 mg/d, and b12 0.5 mg/d had slightly lower rates of depression; there was an impressive 7 year follow-up period
this cross-sectional study using a diet questionnaire found an association between dietary folate & b6 and lower rates of depression in a sample of over 6000 adolescents; no association was found regarding b12.
a study from the American Journal of Clinical Nutrition, which showed a relationship between higher folate and b12 levels, and lower rates of depression, over 7 years of follow-up.
another study finding an association between low b12 & folate levels and higher rates of depression. Here, the b12 association was specifically for women. Looking more closely at the data, I find that the results are not overwhelmingly strong or convincing; I suspect there could be many confounding factors influencing the association.
this is an important study from JAMA showing that high dose folate, b6, and b12 supplements did not improve the course of dementia. Furthermore, 28% of the vitamin group experienced depression, compared to 18% of the placebo group.
http://www.ncbi.nlm.nih.gov/pubmed/18557664this study from the Journal of Clinical Psychiatry showed very little protective effect of vitamin b6, b12, and folate supplementation to prevent depression in older men. However, I see the vitamin group did slightly better than the placebo group, but not well enough to meet criteria for statistical significance.
In summary, there is a little bit of evidence of benefits from b12 in psychiatry, but the results are not overwhelmingly strong unless there is evidence of deficiency. It is worthwhile to have B12 levels checked. It appears not to be dangerous to take supplements; I suppose it is reasonable to aim for the higher part of the recommended serum levels, and to adjust any supplementation accordingly. Having said that, I acknowledge the possibility that some individuals may have a more beneficial effect from b12 supplementation, perhaps there could be selected cases in which this could act synergistically or as an augmentation with other treatments for depression, or perhaps there could be cases of subtle deficiency.
B12 deficiency is not uncommon; this can occur due to malabsorption (as in pernicious anemia or bowel disease), or due to dietary deficiency (e.g. in vegans). If the cause of low b12 is malabsorption, is may be necessary to have b12 injections. Once again, it is important to have b12 levels checked, and make decisions about supplementation if the level is low.