4 ms·

If this effect was large, wouldn't we have spotted it by now? Doctors prescribe antibiotics for nearly anything nowadays. Along the antibiotic, you will get so

by blfr 11y ago

If this effect was large, wouldn't we have spotted it by now? Doctors prescribe antibiotics for nearly anything nowadays. Along the antibiotic, you will get some sort of probiotic (selected strains of bacteria), not to mention all the yogurt and similar products we're eating. Millions of people around the world do it every year. At least some will correctly follow instructions, finish the round of antibiotic, and take the supplement for a while longer. Essentially, we blast and replace bacteria in our guts all the time in a massive natural experiment. Yet I haven't seen any life-changing results.

DanBC 11y ago
It doesn't sound like a plausible mechanism when you first hear it, and so it doesn't get much research. It's not that long ago that we found gut flora that helps cause some obesity; and other gut flora that helps cause normal weight.
- blfr 11y ago
  My point is that you wouldn't need research if the effect was large. If depressed people stopped acting depressed after having a minor infection (treated with antibiotics), they would notice. Their families would notice. Just like people figured out that quarantine works long before we had the germ theory, and without knowing any statistics.
  - Turing_Machine 11y ago
    It took decades to recognize the link between stomach ulcers and bacteria and begin treating ulcers with antibiotics, and that's a lot easier to quantify than mood.
  - peterfirefly 11y ago
    There are many kinds of antibiotics and many kinds of bacteria...
  - Fomite 11y ago
    Keep in mind that you'd need a long term change in your gut flora - a short term disruption by a single course of antibiotics is usually returned to equilibrium in a short amount of time, and would be easily masked by the psychological effects of actually being sick. Longer term microbiome disruptions are also major life events. It's a hard thing to disentangle.
vanderZwan 11y ago
> Yet I haven't seen any life-changing results. Not trying to be a smartass, but "not seeing something" is not really a convincing argument if you have never looked for it before. Especially here, given that there is no obvious feedback loop to give us hints at the relation between the gut flora and our mood. (are you aware of changes in your digestive chemistry and gut flora? How would you connect that to emotional changes then?) But as for evidence: there was that one time during a double blind research trial of a certain experimental probiotic treatment of cancer where the researchers could tell who was in the control group and who wasn't, because the people who got the probiotic treatment were much happier (I saw this mentioned in a New Scientist article on gut bacteria from around 2011 - can't get to it now because it's behind a paywall). Also, the article specifically addresses this: > ‘‘Dr. Lyte,’’ he later asked at a question-and-answer session, ‘‘if what you’re saying is right, then why is it when we give antibiotics to patients to kill bacteria, they are not running around crazy on the wards?’’
- blfr 11y ago
  It's presented as a dismissive question with no answer. But with the number and amount of antibiotics prescribed, wouldn't you expect a lot of curious, seemingly miraculous changes by accident? You know when you take antibiotics. You have a clear time frame, and the event is unusual enough that it should stand out.
  - vanderZwan 11y ago
    Except that for a cause-effect relationship, you need a kind of "all else being equal" scenario. But since we take antibiotics when we are ill, we already are in an unusual state of the body. So any mood swings, if noticed at all, are just as likely (and given that we tend look among the familiar things first, I'd say more likely) to be attributed to things like poor sleep or other side-effects of whatever disease caused you to take antibiotics.
    - blfr 11y ago
      There should be a lasting effect when you replace your gut bacteria, not just some mood swings.
neuro_imager 11y ago
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.

by blfr 11y ago

DanBC 11y ago

It doesn't sound like a plausible mechanism when you first hear it, and so it doesn't get much research. It's not that long ago that we found gut flora that helps cause some obesity; and other gut flora that helps cause normal weight.

blfr 11y ago
My point is that you wouldn't need research if the effect was large. If depressed people stopped acting depressed after having a minor infection (treated with antibiotics), they would notice. Their families would notice. Just like people figured out that quarantine works long before we had the germ theory, and without knowing any statistics.
- Turing_Machine 11y ago
  It took decades to recognize the link between stomach ulcers and bacteria and begin treating ulcers with antibiotics, and that's a lot easier to quantify than mood.
- peterfirefly 11y ago
  There are many kinds of antibiotics and many kinds of bacteria...
- Fomite 11y ago
  Keep in mind that you'd need a long term change in your gut flora - a short term disruption by a single course of antibiotics is usually returned to equilibrium in a short amount of time, and would be easily masked by the psychological effects of actually being sick. Longer term microbiome disruptions are also major life events. It's a hard thing to disentangle.

vanderZwan 11y ago

> Yet I haven't seen any life-changing results. Not trying to be a smartass, but "not seeing something" is not really a convincing argument if you have never looked for it before. Especially here, given that there is no obvious feedback loop to give us hints at the relation between the gut flora and our mood. (are you aware of changes in your digestive chemistry and gut flora? How would you connect that to emotional changes then?) But as for evidence: there was that one time during a double blind research trial of a certain experimental probiotic treatment of cancer where the researchers could tell who was in the control group and who wasn't, because the people who got the probiotic treatment were much happier (I saw this mentioned in a New Scientist article on gut bacteria from around 2011 - can't get to it now because it's behind a paywall). Also, the article specifically addresses this: > ‘‘Dr. Lyte,’’ he later asked at a question-and-answer session, ‘‘if what you’re saying is right, then why is it when we give antibiotics to patients to kill bacteria, they are not running around crazy on the wards?’’

blfr 11y ago
It's presented as a dismissive question with no answer. But with the number and amount of antibiotics prescribed, wouldn't you expect a lot of curious, seemingly miraculous changes by accident? You know when you take antibiotics. You have a clear time frame, and the event is unusual enough that it should stand out.
- vanderZwan 11y ago
  Except that for a cause-effect relationship, you need a kind of "all else being equal" scenario. But since we take antibiotics when we are ill, we already are in an unusual state of the body. So any mood swings, if noticed at all, are just as likely (and given that we tend look among the familiar things first, I'd say more likely) to be attributed to things like poor sleep or other side-effects of whatever disease caused you to take antibiotics.
  - blfr 11y ago
    There should be a lasting effect when you replace your gut bacteria, not just some mood swings.

neuro_imager 11y ago

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.