In this 2016 review, authors discuss the causes of depression and the neurochemical pathways in depression. Providing evidence that vitamin B contributes to the complexity of depressive symptoms specifically vitamins B1, B3, B6, B9 and B12 are essential for neuronal function and deficiencies have been linked to depression.
Mikkelsen K, Stojanovska L, Apostolopoulos V. The Effects of Vitamin B in Depression. Curr Med Chem. 2016;23(38):4317-4337. doi: 10.2174/0929867323666160920110810. PMID: 27655070.