Homocysteine is a bad amino acid associated with heart disease. It is lowered by B12 ( methylated and non methylated depending on MTHFR gene status), B6 and folic acid. High levels are associated with patients who have high creatinine ( impaired renal status) It is seen in patients with depression as well as atherosclerotic heart disease
There is a hypothesis that depression is associated with an imbalance in homocysteine metabolism. Studies show that high levels of homocysteine may be involved in the pathogenesis of depression. Further, approximately 20-50% of patients with severe depression also have elevated plasma levels of homocysteine. Three clinical trials have found that saffron (Crocus sativus, Iridaceae) dried stigmata improves symptoms of mild-to-moderate depression, but the mechanism of action is unknown
Jelodar G, Javid Z, Sahraian A, Jelodar S. Saffron improved depression and reduced homocysteine level in patients with major depression: a randomized, double-blind study. Avicenna J Phytomed. January-February 2018;8(1):43-50. This article was published in the American Botanical Council HerbalGram
The authors conclude that saffron significantly improves homocysteine levels and "has beneficial effects on depression" More needs to be studied on this. The study was a small number of patients.