Can the Bacteria in Your Gut Explain Your Mood? | Hacker News Reader

Can the Bacteria in Your Gut Explain Your Mood?

nytimes.com

96 pointskareemm48 comments

Another thing I've been pondering occasionally is what this and other discoveries might mean if cryonic neuropreservation (head/brain only) storage & reversal is ever practical, or if full head transplants become a viable surgery.

Just how much of actual personness is stored in places other than just the brain? Surely the hormonal (endocrine?) systems of the body, as well as things like the microbiome are going to play important roles, although I have no clue if they're necessary.

In Principles of Psychology, William James speculated that any kind of non-corporeal afterlife would necessarily be non-emotional, since our emotions are felt in our bodies rather than our brains.

If we ever managed to emulate our consciousness on other hardware, wouldn't we be also able to emulate bodily sensations and emotions?

I guess it depends if your emotional configuration is still stored somewhere, or if it was lost when cryo-preserving your head only.

As an ignorant layperson, I kind of assume we could. A virtual machine thinks it has a network card and a hard disk and whatever, but it's just being given what it expects to see.

The problem I was imagining is that right now we're not recording that data in the way that we're, e.g. scanning the brain's neuron connections. So even if we could rebuild/emulated Frozen Jim's Brain, there may be permanent loss of essential information that was distributed around his lymph system or population of gut bacteria such that 'the same person' cannot be reconstructed.

That seems like a rather limited view of location in the opposite. We feel emotion in all of us including our brains.

Antonio Damasio's Somatic Marker hypothesis goes into this and completely changed the way I observed my own mood and emotional state. His book Descartes' Error is a good read if you want to look into it.

This reminds me of the cases where a course of antibiotics for something unrelated cured chronic back pain.

http://www.naturalnews.com/040354_chronic_back_pain_antibiot...

It also reminds me of Russian "phages" bacterial concoctions as cures for certain illnesses. https://en.wikipedia.org/wiki/Phage_therapy

I think this is one of the mechanisms behind detoxifying fasts. Severe caloric restriction for an extended period (I'm guessing at least 3 days) results in major changes in your gut flora, some of which may persist upon resumption of a normal diet.

The problem with this emerging theory about bacteria in the Gut modulating mood, obesity, etc. is very hard to be proved in an absolute way. The number of bacteria's in the gut is extremely high. I think we need much more research on the topic to be absolutely sure we know what we're talking about.

There is a growing awareness about probiotics, but most of the studies I read are not convincing enough, as of today.

It's tricky for mood because you use self-reported descriptions of mood.

But for obesity it's not that hard.

Here's one for anorexia and bulemia. http://www.nature.com/tp/journal/v4/n10/full/tp201498a.html

(my description might be wrong) They start with a prediction; they modify mice and show that prediction is true; they then find human samples (staff and patients at an inpatient ED unit) and they find the staff don't have the particular gut flora while patients do. It's going to be really hard to get ethical approval to give the gut flora to healthy people - to give those people anorexia, so there is a missing step.

I had my entire large intestine removed over several operations, and i felt no difference in my mood

Wow, usually the first step is to prescribe antidepressants

No, it was removed for ulcerative colitis. If gut bacteria affected mood I would have noticed now I have a lot less but there wasn't any change.

Sorry to hear that. My friend has UC and it's a really tough thing to have to deal with. Best of luck to you.

The usual issue is not the overall amount of gut bacteria, but the composition. While bowel surgery can disrupt the composition of your gut flora, it need not have to, and if there was no major accompanying lifestyle changes, it's possible it eventually returned to equilibrium.

It's a little concerning that Mazmanian believes that diet can help autism, when all the placebo-controlled trials show that none of the weird and wacky diets actually work.

While not conclusive, there is actually some evidence a ketogenic diet may help.

As far as I can tell it was uncontrolled, which doesn't really tell us anything (as there will be a large placebo effect).

I believe that for this article placebo controlled trials for fecal transplant are a lot more relevant than diet trials.

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.

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.

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.

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.

There are many kinds of antibiotics and many kinds of bacteria...

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.

> 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?’’

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.

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.

There should be a lasting effect when you replace your gut bacteria, not just some mood swings.

Says who? You could easily imagine your body to acclimatize to new bacteria.

Says the theory that gut bacteria explains mood, the title of the OP.

"Mood" is not a lasting effect.

Well, the people in question are already in the hospital or long term care for some reason, so there's an unfamiliar environment, stresses related to why they're there, etc. Not hard to find reasons for behavior or mood changes there even without addressing the microbiome.

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.

I'm curious why these articles are posted so often on HN. Do a lot of people here have mood disorders? If so, would it not be better to look at the more obvious causes -- lifestyle and stress -- rather than trying to pin the blame on some outside entity?

There really isn't much if any evidence supporting this hypothesis at the moment, and even if there is an effect it appears to be relatively minor.

It likely stems from skepticism regarding the mind-body connection.

There seem to be a lot of bio / pharma readers here, and I appreciate their input into things like this where I might not have otherwise run into them.

In the end medicine comes down to data mining and statistics, with a lot of computer science lineage.

And for that matter, the whole startup scene exists on the wet side of the fence too.

(And also, I suspect that a lot of us here self diagnose our mental state, thus making any information like this of interest.)

As someone mentioned, there's a lot of bio/pharma/med people who read HN, myself included.

Also, if this is true, you're getting closer to being able to 'hack' your own microbiome. Microbiota transplantation as a wetware patch is a pretty cool concept.

I can't speak for anyone else, but personally I really enjoy reading articles on interesting subjects - even if they have no bearing on my own life. That's why I love HN, because you can find interesting articles on subjects that you may otherwise never know anything about.

Knowledge is like fast always on broadband, or a good smartphone. When you don't have it, you have no idea what it can do for you. Once you have it, you wonder how you ever lived without it.

Giulia Enders was recently interviewed on TVO (public television channel in Ontario) that you might enjoy: http://tvo.org/video/213722/giulia-enders-gut-reaction

Vitals by Greg Bear is an interesting (fictional) take on this premise, in which modified bacteria can be be weaponised to influence people's behaviour.

I remember an old saying about drinking the water from boiled potato to improve mood.

No it cannot[1].

[1] See Betteridge's Law.

There is a simpler question - could one tell anxiety from hunger? (I can't) or the feeling of being hungry "reuses anxiety" in context?

This explains why stressed people are overeating - they misinterpret their anxiety as feeling hungry and develop a habit of "eating it over".

Bacteria stuff is just BS.

"Bacteria stuff is just BS."

Why? References?

"There is a simpler question - could one tell anxiety from hunger? (I can't) or the feeling of being hungry "reuses anxiety" in context? This explains why stressed people are overeating - they misinterpret their anxiety as feeling hungry and develop a habit of "eating it over".

Actually it doesn't. Why are they feeling anxious? How do they misinterpret anxiety for the feeling of hunger? Why is the feeling of anxiety and hunger the same (as you assert, I strongly disagree). It is not even close to as simple as you suggest. Maybe bacteria has a role and maybe not. What is known is that the microbiome does have a larger role to play then we currently understand/realize. To what extent and exactly how is still an open question.

Because which set of bacteria one has in ones gut depends of location, season, humidity, air quality, traditional foods, water sources, other bacteria an another hundred factors.

Anxiety disorders are human universal.

Um... When I was suffering very bad anxiety I was unable to keep food down due to the anxiety and it certainly didn't feel anything like hunger.

Reply on news.ycombinator.com