I have not much followed the science of gut microbiome and psychology. Is this really going where this article is pointing? That we can tease out causation in foods and habits via gut microbiome towards behavior and psychology? Pretty rad.

Yeah there's nontrivial evidence that among other things, the complex community living inside you manipulates your brain.

There's a decent amount of research going into the hormones that our GI biome produce and how it affects us. Our body has a few different biomes and they all seem to play somewhat important roles.