The effects, if present, are likely to be nuanced.
It seams likely that these sorts of effects are likely to arise from certain bacteria, and their interaction with other bacteria (as well as presumably a multitude of other factors, such as the integrity of your intestinal mucosa).
Antibiotics (particularly broad spectrum antibiotics) kill entire classes of bacteria (eg. gram positive bacteria - which would include several hundred or thousands of bacteria) and are not good at targeting a specific bacterium.
One consequence of this is the overgrowth of the remaining bacteria (eg. C. difficile which causes pseudomembranous colitis).
So the "massive natural experiment" you describe is not a very reliable one. It may be that when you take a certain antibiotic you kill off all the positive psychobiotic bacteria and the compounds they produce (or maybe just some of them) along with detrimental bacteria (or just one or the other).
You also have to factor in that there are innumerable classes and types of antibiotic, innumerable bacteria (each with their own resistance profile) and variable effects on individuals.
It seams likely that these sorts of effects are likely to arise from certain bacteria, and their interaction with other bacteria (as well as presumably a multitude of other factors, such as the integrity of your intestinal mucosa).
Antibiotics (particularly broad spectrum antibiotics) kill entire classes of bacteria (eg. gram positive bacteria - which would include several hundred or thousands of bacteria) and are not good at targeting a specific bacterium.
One consequence of this is the overgrowth of the remaining bacteria (eg. C. difficile which causes pseudomembranous colitis).
So the "massive natural experiment" you describe is not a very reliable one. It may be that when you take a certain antibiotic you kill off all the positive psychobiotic bacteria and the compounds they produce (or maybe just some of them) along with detrimental bacteria (or just one or the other).
You also have to factor in that there are innumerable classes and types of antibiotic, innumerable bacteria (each with their own resistance profile) and variable effects on individuals.