Abstract:Depression is a common mental disorder. Many patients do not respond to adequate sequential courses of treatment, clinically known as treatment-resistant depression. With further understanding of the mechanisms of depression, non-monoamine hypotheses offer a crucial new dimension for the development of fundamentally novel antidepressant treatments. This paper reviews a large number of studies on antidepressants based on glutamate, opioid and cholinergic systems have been carried out.