Social anxiety disorder-associated gut microbiota increases social fear
107 comments
·June 15, 2025Tarsul
xattt
Sugar? Why not caffeine?
I swear that a 4+ week coffee and caffeinated holiday improved emotional regulation and turns down OCD behaviours and anxiety.
Not sure if this is microbiota-related or related to down-regulation of neuroreceptors activated by coffee compounds.
I’ve heard arguments such as “well… caffeine is cleared within hours so a weeks-long effect is placebo”. Say what you want.
NoPicklez
Well I don't think they're saying that wouldn't happen with caffeine, just that this is their experience with sugar.
cjbgkagh
I believe most people are not notability adversely affected by sugar and a small subset of the population, like myself, are acutely affected. The former does not invalidate the latter. Sarah Wilson of “I quit sugar” fame started off with a zero sugar crusade then later ameliorated her advice in an apparent effort to generalize her advice for a wider audience. I think advice should be tailored by conditioning on what category a person fits into. I would go further and suggest that a zero sugar diet should also have zero fruit. As a ADHD sugar addict I would generally substitute sugar with fruit and that prevented me from finding out that even my ostensibly healthy diet had too much sugar in it.
Tarsul
do you substitute your fruits with vegetables? Maybe I should try it as well but then again my daily apple is one of my highlights.
cjbgkagh
The most direct substitution was cheese, lactose does not appear to have the same effect on me as fructose or sucrose.
I mostly eat kale for vegetables, this also helps with subclinical insulin resistance and inflammation. I think roasting vegetables may end up being too sweet.
I did an extended 5 day water fast to kick start the microbiome changes I undertook it as an experiment and the effectiveness in lifting brain fog suggested that it likely had a microbiome component.
reliablereason
You say sugar, but are you referring to glucose or fructose?
There is a meaningful amount of scientific literature connecting fructose and inflammation.
The AVERAGE human can only digest about 30g of fructose a day. Some substantially more, some substantially less.
A can of soda or three apples is about 30g of fructose.
Inflammation (high- and low grade)then being a second step linking to anxiety.
snovv_crash
Athletes consume 50g of fructose (and 50g of glucose) per hour. It's actually fairly easy to train yourself to this level.
Tarsul
I am talking about the sugar in sweets. My daily apple does not appear to heighten my anxiety.
reliablereason
I have heard people say that eating fibers together with fructose(like when eating a apple) reduces the impact of fructose, as fibers create a lining on the gut wall reducing the absorption rate.
Sounds reasonable. But i have had a hard time finding evidence verifying that hypotesis.
null
iaaan
I recently started consuming relatively large amounts of fiber (standard daily dose of whole psyllium husks mixed with water) and I feel noticeably less anxious than on days when I don't take it. Fiber has been shown to interact somehow (I'm not super familiar) with the body's insulin levels. I wonder if it is related to what TFA is saying.
amelius
I get a similar feeling when drinking milk. Maybe I'm becoming intolerant.
veunes
It's wild how much your gut can mess with your brain chemistry
frankish
Can you explain your jump from gut microbiota to sugar? Aside from sugar being one food that passes through our digestion, I'm not certain why you have singled it out.
kelipso
Just from basic principles, what you eat affects your gut microbiome because different bacteria reproduce more or less from you eating different foods.
jjk166
I think it makes sense that our microbiome should be able to trigger such a response. If your microbiome is changing, it means that some microbe is gaining numbers it didn't previously have, and your current bodily functions, such as your immune system, aren't stopping it. That doesn't necessarily mean your immune system is compromised, but if it is then it would probably be good not to spend a lot of time around other individuals, especially large groups or strangers. Other reasons for your microbiome to be shifting, like a sudden change in diet or enviroment, could also be indicative of an issue like food shortages or territorial change where it would also be good to minimize your exposure to and reliance on others. Finally, depending on what exactly is gaining a foothold, you could potentially be a threat to your kin if you come around them. Developing a social fear response to certain changes in gut microbiome could thus be quite beneficial for most social creatures.
theptip
The problem with Evolutionary Psychology is that it’s easy to construct this sort of “just so” story for pretty much any causal link, and they are not falsifiable.
IMO the simpler hypothesis here is that this isn’t anything adaptive, it’s just another example of how biology is like spaghetti code; changing one chemical signal will affect an essentially random set of downstream systems, some of which can be causally connected to psychology/behavior.
h2zizzle
Could also be like climate change, where it correctly describes a broad phenomenon, but cannot be used to identify or classify any individual event. E.g., Wildfires are probably getting worse because of climate change, but it's difficult to say if the Pacific Palisades fire would not have happened in a cooler global climate.
So, is microbiome-mediated social anxiety selected for as an advantageous trait for societies subject to communicable diseases and the travails of nomadism? Maybe. Did YOUR microbiome-mediated social anxiety arise because it was advantageous for your community? Probably impossible to say.
Also, a hole in GP's logic: you would expect protective social anxiety to arise in people whose situation hasn't much changed except that they've encountered people whose has (as with sedentary villagers encountering nomads who may or may not be about to ransack their settlement).
jjk166
> you would expect protective social anxiety to arise in people whose situation hasn't much changed except that they've encountered people whose has (as with sedentary villagers encountering nomads who may or may not be about to ransack their settlement).
No, you would not expect that. If rats that self-isolate when their gut micro-biomes change avoid diseases that other rats get afflicted with, then evolution will lead to the mechanism spreading through the rats over time. The rats do not need to know why self-isolating helps, they do not need to even know that self-isolating helps, and they do not need to be in the position where it would help the most.
softsound
Wildfires are worse in areas where the wrong type of trees were planted as well which is common in logging areas or places cheaply "reforested" that don't do much research on what should be growing there. Wildfires themselves aren't bad per say either as certain trees only grow from fires. Not to say that climate change isn't a factor though, but there are a lot of varibles too.
asdff
That isn't a problem because no one speaks of these suppositions in terms of "just so" but in terms of "could be due to." If you want to prove something as just so you have to do a lot more work describing a mechanism of action and that involves reaching into a different toolbox.
troll_v_bridge
Which would still be natural selection though.
amelius
Beneficial for the group, not the individual, I suppose.
jjk166
How is it not beneficial for the individual to avoid threats to their health and safety?
MarkusQ
Which is to say, maladaptive. Despite all the people wishing evolution worked at the group level, it doesn't. Groups don't have offspring, individuals do, and thus things that are bad for the individual are extinguished regardless of their effect on the group.
If you look closely enough, even individuals aren't the true units of evolution, for the same reason; competing alleles is where the real action is.
saltcured
When thinking about evolutionary forces, you cannot conflate "positive" outcome with survival and reproduction. An individual might survive and produce offspring via effects that make the individual unhappy in their own life and/or with shortened life.
It's only when an effect causes death or infertility prior to normal reproductive phases that we can really say it has a direct evolutionary pressure. Anything that happens later is always going to be through secondary, social effects on how their condition supports or hinders their offspring from reproducing further generations.
energy123
Alleles are shared with kin which gives rise to multilevel selection effects in rare but real scenarios.
MarkusQ
Voting me down doesn't change the fact that group selection is a myth. A myth that some people are fervently attached to, but a myth nonetheless. Groups simply don't reproduce at a rate or fidelity to allow evolution at the group level over the time scales in question.
E pur si muove.
veunes
Makes me wonder how many other "maladaptive" responses today actually had adaptive roots in a different context
pogue
I've seen probiotic supplements that have strains that claim to help with anxiety and depression, but I've never really looked into them because I'm quite skeptical they do anything. But if anyone is familiar with them and has any feedback I'd be interested to hear it.
kilroy123
I've had a LOT of gut problems in my life. I have a physically broken stomach, have had to have stomach surgery in the past, and probably will have to do it again soon.
Most probiotics I've taken did nothing. The only ones that seem to actually work for me are these: https://drohhiraprobiotics.com/
Not sure why it works, but anecdotally, they do.
Other things that have helped significantly – cutting out alcohol.
h2zizzle
Fermented foods are way more helpful IME. I've even found kombucha protective against mildly spoiled food.
I can also attest to having my first alcoholic drink in a while and it screwing me up for a week.
pogue
I've always been skeptical of probiotic supplements in general mostly because they are stored/shipped in unrefrigerated environments. I believe in most cases the bacteria would end up dead before you even ingested it. However, some companies have developed strains that can withstand some amount of heat. But you never know where they've been stored/for how long/etc.
I remember speaking to someone who had the suggestion to try fermenting food with probiotic supplements, as that would be the only realistic way to know if they were still alive.
There are vendors that do sell probiotic supplements that come shipped in dry ice that people with Crohn's disease & other GI ailments. I don't remember the name of the company that sold them though.
But, I agree that yogurt or saurkraut/kimchi and other fermented products would be a good way to get some gut bacteria. Those would be great to use after you came off antibiotics, but it wouldn't necessarily help with genital mental health/anxiety (as far as I'm aware).
Interestingly, yeast has neurotransmitters and neurotransmitter precursors in it such as tryptophan and serotonin. [1]
Having said all that, I decided to look up the "mood enhancing" probiotic strains I've seen being sold in OTC supplements. The two strains I see are Lactobacillus helveticus Rosell-52 and Bifidobacterium longum Rosell-175 (there may be others I'm unaware of). The studies are quite small, unfortunately. (I didn't read all of them though) [2] [3] [4] [5].
Finally, this is quite a unique term I haven't come across: Psychobiotics!
Psychobiotics are probiotics that have the characteristics of modulating central nervous system (CNS) functions or reconciled actions by the gut–brain axis (GBA) through neural, humoral and metabolic pathways to improve gastrointestinal activity as well as anxiolytic and even antidepressant abilities. [6]
[1] Melatonin and Other Tryptophan Metabolites Produced by Yeasts: Implications in Cardiovascular and Neurodegenerative Diseases https://pmc.ncbi.nlm.nih.gov/articles/PMC4718080/
[2] Assessment of psychotropic-like properties of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects https://pubmed.ncbi.nlm.nih.gov/20974015/
[3] Probiotics Promising for Mild to Moderate Depression https://www.medscape.com/viewarticle/881877
[4] The effect of Lactobacillus helveticus fermented milk on sleep and health perception in elderly subjects https://pubmed.ncbi.nlm.nih.gov/17851460/
[5] One Giant Leap from Mouse to Man: The Microbiota–Gut–Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials https://pmc.ncbi.nlm.nih.gov/articles/PMC8840472/
[6] Exploring the Potential of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 as Promising Psychobiotics Using SHIME https://pmc.ncbi.nlm.nih.gov/articles/PMC10056475/
AaronAPU
yeah I had serious gut problems for years and no probiotic ever did the slightest thing. Anecdotally I can’t differentiate them from snake oil.
But Metamucil changed my life dramatically over a span of a few weeks. Never had the type of symptoms it’s indicated for, which everyone I mention it to just assumes. But it fixed me somehow.
pogue
I was recently talking about fiber & fiber supplements on here in a thread about a new type of fiber that was shown in a study to help with weight loss.
Acetylated cellulose suppresses mass through commensals consuming carbohydrates https://news.ycombinator.com/item?id=44219171
asdff
I'm not sure how many probiotics will make it through the stomach acid. One would think suppository would be vastly more effective: parachute directly onto the battlefield.
Geee
There's this one person who claims to have found out that theses probiotics need to be amplified into a megadose, and subsequently they cured themselves from social anxiety. I'm not sure if there are other people who have replicated, but the initial report seems trustworthy. See https://pdfcoffee.com/experimental-treatment-for-social-phob...
briankelly
I’ve seen people who seem to know what they’re talking about cast doubt that you could create your own probiotic yogurt in a typical kitchen since other strains are likely to dominate without a sterile environment and careful methods.
pogue
That's very interesting. Making your own yogurt sounds like it could be easy to do and you could potentially just use OTC probiotic capsules or powder.
I posted some studies above about two probiotic strains that have specifically been studied for mood enhancement aka "psychobiotics": Lactobacillus helveticus Rosell-52 and Bifidobacterium longum Rosell-175.
bhaney
Whether or not the effect in the paper turns out to be true and reproducible, the supplements you've seen almost certainly don't do anything unless you're wiping out your established gut microbiota with antibiotics first. Your existing microbiota are entrenched and in a very good position to defend themselves from any weakened intruders you might intentionally introduce. Meanwhile, supplement companies really like to make exaggerated claims.
pogue
I posted some links to papers I came across here: https://news.ycombinator.com/item?id=44284165
It's a very fair and valid question as to whether a probiotic supplement:
A) Survives being packaged and stored in a warehouse for an indeterminate amount of time B) Being shipped in the back of a truck/airplane C) If the bacteria is still alive whether it can make it through the GI tract to even have any effect whatsoever
I don't know whether this has been studied. I know Consumer Labs does yearly tests on various supplements, probiotics included, but it's a subscription service and you need to subscribe to see the results. I have subscribed to them in the past and found their testing and articles quite helpful. I
In their tests, ConsumerLab found that the number of viable cells in probiotic products ranged from 1 million to 225 billion per recommended serving.
Additionally, some products were contaminated with harmful bacteria, such as Pseudomonas aeruginosa, which poses a risk to immunocompromised individuals and infants.
The company also noted that the enteric coating of some products did not function properly, potentially affecting the delivery of the probiotics to the gut. (Brave AI Search summary of the article below) [1]
ConsumerLab Tests Reveal Best Probiotic Supplements and Those With Quality Issues https://www.consumerlab.com/news/best-probiotic-supplements/...
kayamon
After trying a lot of things what worked for me was cutting out negative food; usually gluten, lactose, fructose. Probiotics never did anything for me.
BLKNSLVR
What makes gluten a negative food? (outside of being coeliac)
kenjackson
Strongly second this ask.
cwmoore
So long as it isn’t eating the variety of fresh fruits and vegetables that produce gut serotonin in the microbial breakdown of complex carbohydrates and fiber, right?
kenjackson
Why wouldn’t it be? Do you know which ones exhibit the desired characteristic?
vorpalhex
Eating fresh fruits and veggies is a great general health advice but unlikely to shift your gut microbiome meaningfully (unless you are eating some specific fruits or fruit skins in specific conditions).
And randomly eating healthy stuff is probably not going to shift your biome in a particular direction nor eliminate the cause of biome issues.
I eat healthy including a lot of whole fruit, nuts, dried fruits, dark green veggies and grass finished meats and there are still times I have my biome be a bit off.
Agraillo
It's interesting, if we assume that the microbiota "wants" something (like other viruses or bacteria trying to affect the host in some way) and learned it evolutionary then when inside a human it tends to avoid other humans probably due to some disadvantages of the contacts for them. But why? It looks a little strange because humans are highly social species to the edge of survivability so the microbiota just risks losing the host completely.
vslira
I’m writing the following in jest, before anyone takes this seriously, as I assume this kind of correlation has been accounted for.
Maybe the causation is reversed: people who go out more are more frequently infected with all kinds of bugs, from getting too intimate with strangers to eating stuff that was prepared by someone not too assiduous in their hand washing - a sibling reply mentioning fecal microbiota transplant comes to mind
I know this article is about bugs that cause anxiety, but maybe they just lose the competition in a gut environment with the social bugs
People who stay at home are less infected, thus the correlation with these gut specimens
pogue
It's an interesting theory! Maybe find some extroverts and share meals with them & do some consensual saliva exchange with them and pick up their healthy bacteria! :)
ngruhn
This is gonna go viral as: just eat more yogurt to stop being awkward or whatever.
jadamson
Yoghurts probably won't help, but Fecal Microbiota Transplantation might.
A team at the University of Calgary is currently recruiting participants with Major Depressive Disorder and Obsessive-Compulsive Disorder:
https://research.ucalgary.ca/participate/clinical-trial-eval...
https://research.ucalgary.ca/participate/focused-study-fmt-o...
bluefirebrand
Damn, that's my city and I have been struggling with some other stuff
I don't fall under the umbrella of Major Depressive or OCD but if they were doing trials to help anxiety or something I would probably sign up
grafmax
Eating more prebiotics in the form of unprocessed plants is much more effective at improving gut health than probiotic supplements or even probiotic foods. (Of course you can do both.)
mproud
Lotta yogurts people buy are chock full of added sugars.
ninetyninenine
The experiment looked to be the other way around. If you introduced new microbiota from patients with SAD this caused SAD in mice.
So introducing new microbiota won’t solve the problem. The theory that needs to be tested is that we know microbiota can switch SAD on, but does removal of said microbiota turn it off? It needs to be an antibiotic cleansing. It can even be DIY. People can try this on themselves. I think the unknown factor here though is whether or not a persons diet is introducing the SAD causing microbiota.
jvm___
Do we get gut bacteria from the people around us? Where does a newborn get their gut bacteria from?
amanaplanacanal
Newborns get a lot from their mother. They have very little stomach acid, so whatever they are getting goes straight through to their gut.
evanjrowley
It's not just food as many commenters are pointing out. It could be from what people are drinking, even water, if oral delivery is not sanitized.
ninetyninenine
The entry point to the gut is from the mouth so because of that, I think food is where most of the gut bacteria comes from.
hackernewds
we can from kissing
im3w1l
Introducing new microbiota will put competitive pressure on the old one, so I wouldn't write it off with out trying.
kneel
16S sequencing doesn't reveal a mechanism, it indicates a narrow genomic pattern that may or may not be relevant.
ThinkBeat
I feel all such studies should be headlined with: In mice: blah blah blah.
and then if the research is farther along:
In <other animal>: blah blah
and finally if ever
In humans: blah blah blah.
I keep reading storie about what happens to mice in studies but I am far more interested when the research has been able to get to human trials and results are coming in.
afro88
My social anxiety sky rocketed at 19 and didn't start to settle down until 23/24. I never knew exactly why, and that's always troubled me a bit. A microbe population getting out of hand sounds possible, as my diet and surroundings changed drastically at 19. Interesting stuff.
basisword
>> surroundings changed drastically at 19
Couldn't this be the easier explanation? People at that age tend to move away from home, go to college or start work - all big changes, all highly social and potentially stressful changes. Mental health issues leading on from this is understandable and anecdotally I've saw it in several friends.
kridsdale3
People who grew up in a certain SES class (of their parents) also tend to take on poverty-conditions when in college (oh man all I can afford this week are these cup noodles), and not to mention frequent destruction of the microbiome with alcohol. It's probably very disrupting. Maybe has something to do with why those who have a predisposition to having a psychotic break tend to have their first around 20.
veunes
Yeah, the brain might not be the only place we should be looking when it comes to mental health.
chkaloon
Can we just keep taking courses of scorched earth antibiotics until we come up with a microbiome combo that feels good?
orionsbelt
Anecdotally, that generally seems to make things worse, not better.
bhaney
I did this years ago and it seemed to work, but n=1. It took two cycles of antibiotics and intentional introduction of "good bacteria" before I landed on something that seemed to fix most of my food intolerances. Didn't seem to have any impact on anxiety.
I learned later that this is pretty dangerous to attempt, since you're very likely to give yourself c diff or some other infection and end up with persistent IBS before you land on a good microbiome.
SketchySeaBeast
Where does having solid stool sit in comparison to not having social anxiety?
Der_Einzige
Given that it'll cure the latent chlamydia and gonorrhea that people have - not to mention the cat toxiplasmos - lets do it!
hggh
(2023)
I know from personal experience that eating sugar does induce more anxiety in me. This might sound weird but I can "physically feel" in my head a certain anxiety when e.g. I think about something awkward. This "physical feel" stopped being there when I stopped eating sweets for a few weeks. One reason why I try to keep my sugar intake down (the other being in danger of getting diabetes...).
Thus, I wholly believe this study.