New research appears to show that taking a specific kind of probiotic can treat both Irritable Bowel Syndrome (IBS) symptoms and depression. These are the sorts of results many have been waiting for, especially those who sell probiotics, to show a more conclusive connection between probiotic supplementation and mood. But before you rush out to buy a probiotic supplement, we should take a little time uncovering what the study really tells us.

The study included 44 adults with IBS who also had symptoms of depression and anxiety. Half of the group took a daily dose of a probiotic supplement called Bifidobacterium longum NCC3001; the others took a placebo. By the end of the 10-week study, about 64% of those who took the supplement showed some improvements in depression symptoms. The researchers also conduced brain scans that revealed changes in brain areas associated with mood regulation for those who took the supplement.

Just over 32% of placebo group experienced improvements in depression symptoms, about half the rate of the supplement group. Neither group experienced improvements in anxiety symptoms.

So what does this tell us? The researchers feel confident in the results, with senior study author Dr. Premysl Bercik saying in a press statement, “This [study] opens new avenues not only for the treatment of patients with functional bowel disorders but also for patients with primary psychiatric diseases.”

Maybe. But here are a few reasons why that may be a premature assessment.

First, this was a small study, with just 44 total participants, 22 in each group. That fact alone makes makes these results interesting but far from conclusive.

Second, the participants had a combination of IBS and depression and anxiety symptoms. To the extent that the symptoms are linked (i.e. IBS as a possible cause of their depression), it’s impossible to say that probiotics affected depression independently. The supplements may have had a “two birds with one stone” effect (affecting depression symptoms by influencing IBS), which would still be a interesting result, but not the result many are hoping for.

Third, while the brain scan results are intriguing, they aren’t conclusive. Changes in brain areas associated with mood could be attributed to how the supplement influenced the participants' IBS symptoms (or other factors), which in turn affected their mood. Again, it’s impossible to say that the supplement influenced mood independently.

The biggest problem with the results is that they provide shallow evidence for shaky supplement marketing. There’s nothing in this study that “proves” taking this or any probiotic supplement will improve depression symptoms, but you can be sure that’s how the results will be marketed. The term “clinically proven” will appear on a box or bottle with a footnote to this study.

Again, there’s nothing wrong with this study on its own. It shows potentially promising results for those suffering from IBS and depression. But it does not provide proof for claims that probiotic supplementation can treat depression in the general population, nor has any study to date. We’re still in the infancy stage of this sort of research and nowhere near having the results that supplement marketers want to latch onto to sell more product.

Bottom line: taking probiotics to treat depression probably won't hurt you, but there's little reason to think they'll help you either, at least not yet.

The study was published in the journal Gastroenterology.

David DiSalvo, Contributor