There were some amazing statistics in an article I spotted today on the website, Psychiatry Advisor[i].
Not to make a bad pun here but… how depressing is all of that?
The article then goes through some of the studies in the medical literature supporting the use of probiotics to treat depression.
One large meta-study analysis[ii] (reviewing 10 other studies that covered a total of 1349 patients) just published found that probiotics did not significantly improve mood but in a subgroup analysis, comparing those with mild to moderate depression to those without depression, they found that actually, the improvement was significant. There were several limitations to this research, as the authors note, including the fact that different doses and types of probiotics were used in the various studies.
Other meta-analyses have concluded that probiotics are indeed helpful, including another large one covering 5 studies. And there are individual studies, including double-blind-placebo-crossover (the gold standard in science) that show efficacy, including an 8 week long one in which patients with MDD [major depressive disorder] were given a probiotic containing Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum. While on the probiotic, as opposed to the placebo, patient showed marked and measurable improvement in depressive symptoms.[iii]
In November 2017, a paper[iv] came out describing the relationship of the bacterial microbiome to depression and schizophrenia. They concluded that “…the microbiota has become a valid target in the search for effective treatments for schizophrenia and MDD.” Unfortunately, they also state: “To date, only very few well-controlled clinical studies have been conducted, and the results from different clinical trials were not always consistent.”
Studying probiotics for any illness is an incredibly complex thing in that you have to determine the best strains, consider interactions between strains, figure out the dose of each strain, determine any other compounding factors (i.e. diet, prebiotics, etc.) that might affect their use, and so forth. However, there is certainly enough in the literature at this point to warrant using a good quality probiotic to treat depression, even if it’s an adjunctive therapy…especially since there is no downside. Remember my mantra:), “If it can’t hurt, and it could help, do it.”
[ii] Ng QX, Peters C, Ho CYX, Lim DY, Yeo WS. A meta-analysis of the use of probiotics to alleviate depressive symptoms. J Affect Disord. 2018;228:13-19.
[iii] Akkasheh G, Kashani-Poor Z, Tajabadi-Ebrahimi M, Jafari P, Akbari H, Taghizadeh M, Memarzadeh MR, Asemi Z, Esmaillzadeh A. Clinical and metabolic response to probiotic administration in patients with major depressive disorder: A randomized, double-blind, placebo-controlled trial. Nutrition. 2016;32:315–20. https://doi.org/10.1016/j.nut.2015.09.003.
[iv] Fengli, L, Suling, C, Wang, L, Jiang, R, Tian, H, Li, J, Yao, Y, Zhuo, C. The role of microbiota in the pathogenesis of schizophrenia and major depressive disorder and the possibility of targeting microbiota as a treatment option. Oncotarget. 2017. 8(59(:100899-100907.