depression
"I began taking niacin 2 years ago for high cholesterol and after 3 months of taking the vitamin at 500mg/day my cholesterol levels dropped from 260 to 210 with improved ldl and hdl also.  I upped the dose to 1000mg a day and have taken for 2 years with current chol level of 189. 

I not only noticed a reduction in cholesterol but began to feel better and happier.  I stopped taking niacin last month and after 1 week started to experience previous anxiety and depression problems that I had been plagued by prior to niacin.  I had no idea niacin was so effective in helping with depression until I stopped taking it.  I'm back on it and have no worries.  "