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A Gut Feeling
The title, Campylobacter jejuni infection increases anxiety-like behavior in the holeboard: Possible anatomical substrates for viscerosensory modulation of exploratory behavior, is unpromising but the paper is fascinating. The authors show that infection with certain bacteria can cause more anxious or cautious like behavior in mice, perhaps causing the infected agent to avoid predators.
The presence of certain bacteria in the gastrointestinal tract influences behavior and brain function. For example, challenge with live Campylobacter jejuni (C. jejuni), a common food-born pathogen, reduces exploration of open arms of the plus maze, consistent with anxiety-like behavior, and activates brain regions associated with autonomic function, likely via a vagal pathway.
Could bacteria also influence our emotional state? If verified in humans this could offer insights into conditions like Crohn's disease, irritable bowel syndrome and perhaps into fears such as agoraphobia. Long time readers will know that this study is not alone in suggesting that parasites can influence our emotions. Ever wonder why you like cats?
Hat tip to Monique van Hoek and Faculty of 1000.
Posted by Alex Tabarrok on December 7, 2007 at 11:03 AM in Food and Drink, Medicine, Science | Permalink
Comments
Re: Could bacteria also influence our emotional state?
Not sure why you might think this to be a surprising idea. It is well known that exercise influences emotions, and food and drink, too. In fact, many substances are ingested with the specific intent of affecting emotional states. With bacteria the influence may be less direct, but if they affect what kinds of chemicals get passed into the bloodstream, they could readily affect moods.
Posted by: Mike Giberson at Dec 7, 2007 11:35:55 AM
Sorry for the faulty HTML.
Posted by: Mike Giberson at Dec 7, 2007 11:37:18 AM
Alcohol doesn't want to make me drunk and I get to decide whether to imbibe!
Posted by: Alex Tabarrok at Dec 7, 2007 11:49:57 AM
There is already a lot of research showing that parasites can influence the behaviour
of their host species in ways that are beneficial to the parasite. For example, rats
infected with toxoplasma gondii are less fearful of open spaces, and so are more
likely to be eaten by cats. The parasite then gets into the cat.
http://en.wikipedia.org/wiki/Toxoplasmosis
Wolbachia (http://en.wikipedia.org/wiki/Wolbachia)infects insects and does truly
wacky things.
A few months ago there was an article showing that colonization with soil organisms was associated with increased production of certain neurotransmitters, lowering depression.
Perhaps the romantic association with the land has some biological basis!
Posted by: SJE at Dec 7, 2007 11:51:41 AM
Or even more creepy, a parasite that has been
linked to schizophrenia in humans might be changing the behavior of rats and
making them more more vulnerable to predators.
Posted by: mobile at Dec 7, 2007 11:52:34 AM
as far as i know, crohn's disease and IBS are autoimmune issues, but of course they could be related to bacteria
Posted by: michael k at Dec 7, 2007 11:54:05 AM
Dan Dennett takes this view of bahavior and expounds it to memes: viruses of the mind, not the brain. This great talk of his at TED shows how some wierd behavior is just a fluke. No really: it's a fluke. http://www.ted.com/index.php/talks/view/id/116
Posted by: Thayne at Dec 7, 2007 12:16:29 PM
Interesting
Posted by: Michael Foody at Dec 7, 2007 12:50:55 PM
Crohn's has been linked to infection with Mycobacterium, and the resulting
overactive immune response. This link, however, has not been proven, as some assert that the organism infects a weakened host.
I should note, however, that the medical profession has a lot of resistance to the idea
that microbes underlie chronic disease. Mostly, it is because of their training and
perspective (seeing a disease within a certain paradigm accepted by your peers) but there is also a strong amount of self interest. If you can cure stomach ulcers with antibiotics instead of a life-time of medication, the gastroenterologists are out of a lot of $
Posted by: SJE at Dec 7, 2007 12:58:02 PM
Well, the causation is quite plausibly not a direct modification of neurology, but a rational response by the mice to feeling unwell.
Let's look at humans. Most humans, when feeling sick, show a greatly reduced interest in exploring new and novel spaces. People rationally conclude that, hey, I'm sick, I need to be around other people in case I get really sick. (I think this is a much more instinctive reaction than anything especially rationally thought out.)
Many stomach ailments cause chronic pain and discomfort, the mouse brain is likely interpreting this signal as a reduced fitness level and ability to escape predators.
The response to chronic pain (ie reduced activity) is a plausible design flaw in humans and other mammals.
I tweaked my knee once and it would give out while walking down stairs. The reality was my knee was strong enough to not give out, but my "knee system" was designed to not take the chance of a catastrophic failure and gave out early. I had no conscious control of this system -- except to undergo the months of physical therapy to correct the problem.
Chronic-pain induced anxiety sounds like a similar system. An overreaction by the organism, but in the rough and tumble world of evolutionary design probably a wise design decision - since anxiety is highly survivable, however unpleasant it might be for the organism.
Posted by: jim at Dec 7, 2007 1:27:24 PM
The real question is whether or not I can use this to create an army of flesh-eating zombies?
Posted by: Daniel at Dec 7, 2007 1:39:58 PM
Attempting to close the italics tag:
For those interested, Paul Ewald has done a lot of work on the relation between infectious disease and chronic illness.
Posted by: Jonathan Miller at Dec 7, 2007 1:40:44 PM
? maybe that'll do it
Posted by: Michael Foody at Dec 7, 2007 1:48:28 PM
I know not everyone has access to online journals, but if you want a quick review see
Behavioural Processes, 68, (2005) issue 3 for lots of papers to read.
Posted by: rhodium at Dec 7, 2007 1:49:33 PM
Italic close attempt. :)
Posted by: Sebastian Holsclaw at Dec 7, 2007 2:15:18 PM
There!
Posted by: ziel at Dec 7, 2007 6:00:28 PM
Well this thesis is totally plausible. But what are Indian yoghi doing when
they seat under a sychomore three apparently
meditating, the phalanxes of their thumb and forefinger bent and touching
each other as if they were making the "OK" sign?
Posted by: sabina at Dec 7, 2007 6:35:39 PM
Intestinal health is one of the best predictors of mood as it is one of the largest areas determining serotonin release in your body. Also, beyond basophils, the intestine is the 2nd biggest site for histamine release causing inflammatory processes associated with Crohn's, "IBS", etc. and explains why symptoms can be so varied individual to individual. I could definitely see how alterations in the normal flora of your body could lead to emotional distress, as well as a plethora of other possibilities.
The problem goes both ways as well. Your digestion as well as immune system work via parasympathetic activity(acts to calm, relax, digest, and maintain homeostasis/autonomic balance). If you are stressed, you increase the sympathetic tone of your body, thus inhibiting digestion, proper immune functioning, etc making you more susceptible to irritability, anxiety, and disease.
In Spontaneous Healing by Dr. Andrew Weil (a world leader in holistic/integrative healthcare) and a TIME magazine top 100 most influential persons, proposes that medical doctors are ill-equipped for chronic degenerative diseases, or forms of allergic/autoimmune diseases, and that alternative practitioners are probably your best source of treatment during these conditions - and he' a highly respected M.D. himself! A lot of intestinal disturbances deal with these types of isses, yet too few people utilize or are aware of the other options available to them in chiropractic, accupuncture, nutrition, etc who are more specialized to deal with these issues.
Posted by: Alexander Rinehart at Dec 7, 2007 7:12:46 PM
This explains why all those sick folks in hospitals are always so grumpy..It's scary that there is a crossover from the physical to physiological, where an outside organism can influence your brain's functions. I am most certainly thankful for having a decent immune system that fights off these micro-depressors. And, on that note, would this also mean that people whom have better immune systems are hapier and more stress free than those who inefficiently fight infection? I think that more people should be made aware of this problem in order to better prepare them for small changes that we can all make to allow for a happier collection of healthy and bacteria free individuals.
Posted by: chase at Dec 7, 2007 11:51:07 PM
A low level of vitamin B12 causes irritability. Vitamin B12 is produced
by a well functioning intestine. Prolonged lack of vitamin B12 affects your
immune system and leads to degenerative illness such as fibromioalgia (and
from there to sclerosis, probably) and pernicious anaemia.
Posted by: sabina at Dec 8, 2007 5:39:37 AM
There is a first-rate book about the interactions between us and bacteria just out, Good Germs, Bad Germs by Jessica Sachs.
Posted by: Tim Lundeen at Dec 8, 2007 8:20:33 PM
Consequences of interrupted digestion: DOCTOR HOUSE, season 1, ep. 14.
Posted by: sabina at Dec 9, 2007 5:55:22 AM
Dear "chase": If you were bacteria free, you would not be healthy, you would die. Mammals need their microbiotic flora to survive!
Posted by: A_Female_Brain at Dec 9, 2007 12:15:23 PM
Consider also reading this from Survival of the Sickest blog, that is about another common bacteria that looks like inflence people mood. It could even explain the recent increase of depression prescription by the doctors.
http://survivalofthesickestthebook.com/blog/?p=146
Posted by: Fred at Dec 10, 2007 3:07:01 PM
Toxoplasmosis has been linked to schizophrenia, risk aversion, neuroticism, heightened extraversion and promiscuity (in women...can we bottle it). This is predominately because the parasite releases dopamine. There is quite a body of literature, just google 'toxoplasmosis dopamine' and you will come back with over 90000 hits. A biologist for the USGS recently found a strong, positive correlation between toxoplasmosis infection rates and neuroticism on a nation by nation study. For a good overview of how parasites have 'guided' our evolution, read Carl Zimmer's Parasite Rex.
Posted by: David at Dec 12, 2007 4:27:46 PM
