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Posttraumatic stress disorder can be treated with bacterium from the soil

Posted May 20, 2016

Posttraumatic stress disorder develops after traumatic events and can change life of the person forever. It is a mental disorder, which is hard to treat. Now scientists from the University of Colorado Boulder found that injecting mice with a UCL-discovered bacterium can reduce stress and inflammation, which helps preventing PTSD-like conditions.

Mice treated with Mycobacterium vaccae were much better in a stressful situation, showing less fear and anxiety. Image credit: Ciotu Cosmin via Wikimedia, CC BY-SA 4.0

Mice treated with Mycobacterium vaccae were much better in a stressful situation, showing less fear and anxiety. Image credit: Ciotu Cosmin via Wikimedia, CC BY-SA 4.0

These mice used in the study started being less afraid and anxious in stressful situations. Furthermore, this bacterial immunization managed to alter the serotonin activity in the brain – effects were similar to those of anti-depressants or long exercising. Mice that were not immunized also suffered from worse cases of colon inflammation as they were worsened by stress. All of this means that the discovery of this bacterium is very important.

Mycobacterium vaccae can be found naturally in soil. Professor Graham Rook, who investigated immunological properties of this bacterium, said: “Previous research has found that US Marines with evidence of inflammation in their body are more likely to develop PTSD*, and the latest work suggests that bacterial immunization might help to reduce this risk. It shows that M. vaccae simultaneously prevents colitis and psychiatric symptoms by switching on regulatory pathways in the immune system”. Interestingly, this new study builds on the ‘old friends’ hypothesis, proposed back in 2003.

‘Old friends’ refer to a rich variety of microorganisms living in human bodies and contributing to immune system development. Back in a day when humans depended more heavily on nature for food, our bodies were full of such microorganisms from soil. Without them nowadays, we are facing a greater risk of various inflammatory diseases and even psychiatric conditions. This is why this research also suggests re-introduction of these ‘old friends’ in order to improve physical and mental health of humans.

One of such ‘friends’ could be M. vaccae bacterium as this study showed. Scientists gave some mice either a dose of bacterium or a placebo and then kept them either individually or with a dominant male, which is very stressful. Mice that have been given M. vaccae felt much better – they were less fearful and calm. Therefore, scientists think that there is a potential for development of a drug therapy that would help people combat long-term anxiety and depressive-like symptoms. However, M. vaccae is not a vaccine as it does not targets any antigens. Instead it evokes particular immunoregulatory responses, which prevents inappropriate inflammation.

We as people are trying to protect ourselves from bacteria. However, a lot of them are actually beneficial, as was demonstrated with this new study. A lot of steps remain to be taken to turn this concept in to an actual drug therapy, but we can only wait and see into what this research will develop.

Source: UCL

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