“I’m convinced people’s parasites walk them to Baskin-Robbins.”  That’s what my nutritionist said in a discussion of how mircoorganisms – including bacteria, fungus, viruses, and parasites – affect behavior.  One of the themes I wish to document on this site is the research in this area, and perhaps my own theories.  I think we will see a lot of research in this area in the near future.  To me this has always seemed obvious: organisms living in one’s body area clearly going to have a physical effect, and in the body there are physical mechanisms related to mood, hunger/cravings, desire, etc.  So it’s likely that the physical effects of microorganisms will manifest in changes in these aspects leading to changes in behavior.

Today Science reported:

Mice whose diets were supplemented with L. rhamnosusfor 6 weeks exhibited fewer signs of stress and anxiety in standard lab tests, Cryan and colleagues report online today in the Proceedings of the National Academy of Sciences. For example, the rodents spent more time exploring narrow elevated walkways and wide-open spaces, which are scary to rodents, and they exhibited a smaller spike in stress hormone levels when the researchers put them in water.

Source: Mind-Altering Bugs

Primary Source: Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve

Now I do want to be clear that I do not support animal experimentation such as this.  I believe studying humans is the best way to gain knowledge about humans, perhaps supplemented by observational research of other species.  Perhaps that is something else I will write about in detail at some point.  Some would argue that using knowledge gained in an unethical way is itself unethical.  I will sidestep that argument with the argument that much animal experimentation is repetitive and redundant so one of the best things to do from any animal experiment is to publicize the results so that the same experiment is not run dozens, if not hundreds, more times (for example primate nicotine research).

One positive aspect of this study is that they mention that microorganisms may provide a therapeutic role in the body.  Since people are often unnerved by the idea of organisms living inside of them I think this is a good finding to highlight.  This does not mean, contrary to the write-up in Science, that these organisms are “beneficial”.  Reducing stress is not beneficial if the stress is the correct/adaptive response as it may have been in the case of this experiment.  Stress does serve a useful role in preparing the body to face danger.  The problems related to stress in human civilization is the pervasive perception of danger that leads to constant stress and the damaging effects caused by prolonged stress.  So, yes, the right microorganisms might help humans to have a healthier relationship with stress and the wrong microorganisms may contribute to various stress-related disorders.