Introduction: Elevated homocystein take place in degenerative processes like dementia and cardiovascular diseases. But, the relation between depression and homocysteine is still being investigated. It is long known that deficiency of folic acid or Vitamine B12 may cause depression. It is in fact difficult to interprete the role of homocystein in depression since the deficiency states of these substances also produce elevated homocystein levels. The aim of this study is to show the effect of major depression and its treatment in the levels of homocystein, folic acid and Vitamine B12.