It came as no surprise to me that the systematic review and meta-analysis article by Jerome Sarris and colleagues  found what it did in relation to the use of [certain] adjunctive (add-on) nutraceuticals alongside antidepressants to reduce depressive symptoms: some of them might actually be clinically useful.
With no medical or clinical advice given or intended, the authors report that "adjunctive use of SAMe, methylfolate, omega-3, and vitamin D with antidepressants" might be something to consider "for improving inadequate response to antidepressants." Dr Sarris was one among many authors who contributed to the 'personal view' paper titled: 'Nutritional medicine as mainstream in psychiatry'  which was also covered a while back on this blog (see here). This latest addition to that and other opinions  which covered the peer-reviewed literature on a variety of nutrients also found something of a mixed bag of results for various other compounds including the aromatic amino acid tryptophan, zinc, folic acid and vitamin C.
Quite a bit more science needs to be done in this area, not least around the hows and whys that the various preparations might exert some effect. Vitamin D has of course been covered quite a bit on this blog in relation to something like depression (see here for example) so that particular nutraceutical might already have a research head start compared to others. I'm also minded to suggest that the involvement of something like SAMe (S-adenosylmethionine) as an add-on treatment might also imply a role for epigenetic variables in relation to at least some depression . And then there is the question of who might be best responders to such nutraceutical use which implies heterogeneity and possible plural depressions...
 Sarris J. et al. Adjunctive Nutraceuticals for Depression: A Systematic Review and Meta-Analyses. American Journal of Psychiatry. 2016. April 26.
 Sarris J. et al. Nutritional medicine as mainstream in psychiatry. Lancet Psychiatry. 2015 Mar;2(3):271-4.
 Sarris J. et al. International Society for Nutritional Psychiatry Research consensus position statement: nutritional medicine in modern psychiatry. World Psychiatry. 2015 Oct;14(3):370-1.
 McGowan PO. & Kato T. Epigenetics in mood disorders. Environ Health Prev Med. 2008 Jan;13(1):16-24.
Sarris J, Murphy J, Mischoulon D, Papakostas GI, Fava M, Berk M, & Ng CH (2016). Adjunctive Nutraceuticals for Depression: A Systematic Review and Meta-Analyses. The American journal of psychiatry PMID: 27113121