We’re learning exciting new things about the microbiome all the time. As a psychologist and a neuroscientist, I’m most interested in how the bugs in our guts can affect our brains and our behaviour. With some help from my colleagues (including the wonderful Bridget Callaghan, of the Two Brains blog), I’ve been testing out some ideas about how a probiotic treatment can help infant rats recover from the effects of early-life stress. We’ve even tested this probiotic treatment against the generational effects of stress, which are also observed in people. For example, a recent large-scale study showed that childhood wartime evacuation increased mental health risk for girls and, much later, their daughters.
The probiotic treatment we used is made up of two specific bacterial strains – Lactobacillus rhamnosus and Lactobacillus helveticus. This is important because not all bacteria are the same, which means that not all probiotics will have the same effects. In this case, our chosen probiotics worked to prevent stress-induced changes in the rats’ fear memories.
What exactly does that mean? Well, the stressed infant rats tended to remember bad experiences for much longer than normal. We think that this might be a clue as to why individuals who experience early adversity are more vulnerable to anxiety. But the probiotic treatment reduced this indicator of vulnerability – stressed infant rats that received probiotics went back to normal levels in terms of the persistence of their fear memories. If you’re interested in seeing the research article, it’s available here.
What was really remarkable was that we could observe the same patterns in the next generation (see here for the research article). The offspring of stressed male rats also had unusually strong fear memories, even though this next generation never directly experienced any stress. But again, we could prevent this by giving the probiotic treatment either to the stressed fathers or directly to the next generation. This is really exciting stuff! Who would’ve thought that these microscopic bugs could be powerful enough to reduce not only our fears, but our children’s fears too?! But before I get too carried away, there are some caveats…
We don’t yet know exactly how this probiotic treatment causes changes in behaviour across generations. One possibility is that there might be epigenetic changes, as discussed by Dr Emma Beckett in a previous MindBodyMicrobiome article. Alternatively (or in addition), the treatment might work through changes in the immune response or altered parental behaviour.
Finally, I want to point out that we also don’t know whether these findings can be applied to people. There are lots of differences between laboratory rats and our own complex emotions and behaviours. So, while I don’t think that probiotic supplements are the solution to life’s stresses, I’m hopeful that one day investigations like this will lead to a better understanding of how we can train our gut microbiota to help us minimise the harmful effects of stress.
Caitlin is a post-doctoral research fellow at the APC Microbiome Institute at the University College Cork (Ireland). You can find her on Twitter @caitlincowan3.