Irritable bowel syndrome (IBS) as a risk factor for bipolar disorder

"Only irritable bowel syndrome (IBS) emerged as a risk factor for BD [bipolar disorder] supported by convincing evidence."

So said the results of the umbrella review of systematic reviews and meta-analyses by Beatrice Bortolato and colleagues [1] looking at the various environmental risk factors potentially linked to the diagnosis of bipolar disorder. I might add that this is a topic that has been discussed before on this blog (see here and see here for examples).

If the systematic review / meta-analysis represents the top of the research methodology hierarchy, a review including a number of systematic reviews and meta-analyses represents the cherry on top. Indeed, there is a growing trend of this kind of research (see here).

The authorship names included on the Bortolato paper are not unfamiliar to this type of study methodology (see here) and specifically, the focus on psychiatric and somatic variables often being intertwined. This time around attentions turned to bipolar disorder, previously called manic depression, and a survey of 16 research publications identified listing over 50 "unique environmental risk factors for BD." The report of a possible link (with 'convincing evidence') between IBS and BD consolidates the idea of a gut-brain axis. Authors also detailed a few other factors as showing weaker but not necessarily less important connections to BD including childhood adversity, obesity and asthma. Focusing in on asthma in particular - a condition again previously talked about in the context of BD - I am wondering whether there are quite a few more generalisations connected to this diagnosis within the context of psychiatric labels (see here and see here)?

Of course, more science is indicated on the hows-and-whys of connections such as the one between IBS and BD and the tantalising prospect of new intervention avenues if such a relationship is further confirmed. Minus any medical or clinical advice, I'm specifically thinking about how alterations to the gut microbiome accompanying cases of IBS might mean that talk of things like probiotics affecting the symptoms of IBS (see here) could be applicable to the presentation of [some] BD too. That and the idea that certain dietary elements might also be important to cases (see here and see here)...

To close, I know that the past few days have not exactly been ones for smiling, but if some smiles and laughter are what you need, then the animal kingdom can provide them...

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[1] Bortolato B. et al. Systematic assessment of environmental risk factors for bipolar disorder: an umbrella review of systematic reviews and meta-analyses. Bipolar Disord. 2017; 00: 1–13.

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Bortolato, B., Köhler, C., Evangelou, E., León-Caballero, J., Solmi, M., Stubbs, B., Belbasis, L., Pacchiarotti, I., Kessing, L., Berk, M., Vieta, E., & Carvalho, A. (2017). Systematic assessment of environmental risk factors for bipolar disorder: an umbrella review of systematic reviews and meta-analyses Bipolar Disorders DOI: 10.1111/bdi.12490