The biggest nutritional cause of depression is folate deficiency. A doctor back in 1962 put himself on folate-free diet. After 4 months he was severely depressed. Unfortunately, most people suffering depression have normal blood levels of folate. Folate is vitamin Be and occurs naturally in spinach and other green veges. A synthetic form called folic acid is given to pregnant women to prevent birth defects. A recent discovery that about 70% of Americans have a genetic mutation that prevents or limits the transformation of folate/folic acid to the active form L Methylfolate. The active form is a necessary precursor to production of serotonin, dopamine and norepinephrine. A new "medical food" called Deplin is not a drug. It is activated vitamin but requires prescription. When Deplin is added to an SSRI, there are surprising improvement in depression. Google Deplin and you can find lots of information about it.