Hello & Welcome, Obsidianbutterfly! In my particular case a B-12 (cobalamin) problem is related to my depression. I suffer from autoimmune pernicious anemia (PA). Basically, I cannot absorb B-12 through digestion; I receive monthly B-12 injections.

A gastroenterologist diagnosed the PA a few years after psychiatrists identified my depression, although it is likely the PA was present much earlier. Unfortunately, having received the depression diagnosis, the medical professionals tended to attribute all my symptoms to the depression. That delayed the PA diagnosis and the initiation of B-12 treatment.

Also unfortunately, B-12 treatment has had no effect on my depression.

I wish you better outcomes.