B12 and Depression

I've been really struggling for the past month or so with my emotions.  I finally decided I needed to do some research today to see if I could find anything to help.  Of course I came across lots of information about B12 and depression.  One website even had the following information:  "While most doctors would never consider such a possibility, studies have documented local cerebral deficiencies of B12 (using cerebrospinal fluid levels as a measure) in people with alzheimers, and people with brain atrophy." So the dosage that seemed to be recommended was at least 2000mcg per day.  I checked my medication list which I have on my computer, and it said I was taking 2000mcg daily.  Then I checked my pill box, and discovered that somehow over the past few months, I've changed and am only taking 125mcg a day.  I imagine I saw a good sale on B12, and forgot that I needed the higher dosage.  So hopefully my tears will dry up and blow away!