In recent years, our gut microbiota has been shown to have an amazingly wide-ranging impact on our body’s overall function. Indeed, it seems hardly a week goes by before another health-determining mechanism is found to be linked to the 100,000 billion microorganisms that inhabit our intestines. Originally thought to be limited to digestion, the effects of our microbiota have since been extended to immunity, prevention of chronic disease, inflammation, mood disorders, and regulation of the nervous system. Now we learn that our likelihood of suffering post-traumatic stress disorder (PTSD) is also influenced by the composition of our gut microbiome sup>1.

Importance of healthy microbiota

Even if you’re unfamiliar with this common disorder, you could potentially fall victim to it if you’re unlucky enough to suffer a traumatic event such as a car accident, physical and sexual abuse, or a natural disaster of some kind. It’s a widespread condition that causes recurrent symptoms such as nightmares, repeated and invasive memories, avoidance, emotional changes and hyperactivity of the nervous system (irritability, difficulty concentrating, hyperarousal …). However, not everyone will be affected: following the same traumatic event, one person may go on to develop PTSD, while another may escape it completely. This is not simply down to chance: scientists had hitherto observed that bad childhood experiences as well as an unhealthy lifestyle could tip the balance in determining an individual’s fate. Now a new factor further repudiates the role of luck in developing the disorder: the quality of our microbiota.

The scientists responsible for this finding identified a significant difference between the microbiota of PTSD-sufferers and that of individuals who had not developed the disorder following a traumatic event. The PTSD patients had far lower levels of Actinobacteria, Lentisphaerae and Verrucomicrobia, three types of bacteria known to play a role in immune system regulation and modulation of inflammation levels. During a period of traumatic stress, the researchers clearly observed exaggerated inflammatory responses as well as an alteration in regulatory T cells which combat the abnormal immune responses seen in allergies, auto-immune diseases and transplant rejections^2-3. They also noted that individuals who before the traumatic event exhibited raised levels of C-reactive protein (a reliable marker of inflammation) were more likely to suffer post-traumatic stress⁴.

Our bacteria and nervous systems communicate with each other

This study underlines the fact that the gut microbiota communicates with the central nervous system. Adverse changes, as a result of antibiotics or an unhealthy diet for example, can be expected to have direct consequences on cognitive function⁵, on the hypothalamic-pituitary-adrenal (HPA) axis, also known as the stress axis, and via a domino effect, on the body’s ability to either prevent or precipitate certain diseases⁶. These effects on the central nervous system themselves have repercussions for the microbiota, creating a destructive vicious circle⁷. For example, glucocorticoids secreted by the body during periods of stress stimulate the growth of a pathogenic bacteria called Helicobacter spp, which in turn promotes and aggravates all types of chronic inflammatory disease.

The good news is that you can do something to restore ‘friendly’ bacteria in the microbiota and thus reduce the risk of both post-traumatic stress and chronic inflammatory disease. Probiotics are microorganisms that positively influence the microbiota by eliminating pathogenic species.