HOW THE GUT MICROBIOME COULD AFFECT PERSONALITY

You are what you eat: how the gut microbiome could affect personality.

The microbiome consists of trillions of microorganisms including bacteria, fungi, parasites and viruses. The largest number of these microbiota are in the small and large intestines, forming a symbiotic relationship with the human body in which both benefit from their relationship.

The microbiota are given a prime habitat in which to thrive, and, in doing so, carry out a range of functions such as stimulating the immune system, breaking down compounds from foods that may become toxic, and synthesising certain vitamins and amino acids. If there is a disturbance in the balance of microorganisms in the gut due to infectious illnesses, certain diets and bacteria destroying medications, dysbiosis occurs and the body may become more susceptible to disease.

The ratio and strains of microorganisms present are due to a number of factors. Scientists estimate that 50% of this is down to genetics, however the microbiome can also be affected by diet and medication Antibiotics and other medications that kill bacteria have the most notable effect, decreasing the diversity and size of the microbiome, however probiotics can introduce bacteria and scientists also suggest consuming 30 different plants (including fruits, vegetables, grains and nuts) a week for optimal gut health to increase biodiversity.

Whilst it is well known that this supporting organ has big effects on the health of an organism, studies have also more recently begun to look into its effects on personality. A wide range of studies have found links between personality and specific bacteria present in the gut, for example, those who are more sociable have been found to have a microbiome containing more diverse bacteria and larger numbers of it. The reason for this is still unknown, but some theorise that this is because being sociable increases exposure to bacteria, allowing for optimal gut health.

Dr Katerina Johnson of Oxford University’s Department of Experimental Psychology carried out an investigation of the effect of gut microbiome on personality in humans She found that gut microbiome composition and diversity were related to differences in personality. Most notable sociability and neuroticism. Research into the microbiome-gut-brain axis (the connection between gut bacteria and the brain) is increasing as further correlation between types of microbiota present and mental health conditions are found. Some studies have gone as far as to transplant the microbiota from one organism to another When researchers transferred faecal microbiota to a mouse strain known to be more “anxious and timid” from a strain of “bold and exploratory” mice, the timid mice showed decreased levels of anxiety and researchers noticed they became bolder The same results were found when bacteria was transferred the other way - the bold mice became less exploratory. This study suggests that the microbiota present are not just correlated with personality, but are a direct cause.

DR DOLPHIN: THE HUMAN BODY

Whilst it is still unclear how every individual strain of microbiota affects brain function, there are multiple possible mechanisms that could cause this Microorganisms may communicate with the brain via neural, immune and endocrine pathways and produce neuroactive chemicals that can modulate host neurotransmitter levels. It has been found that the levels of some types of bacteriodes in the microbiome are associated with the brain signatures of depression. GABA, a neurotransmitter that blocks impulses between nerve nerve cells in the brain can be bacterially derived People with anxiety and depression have lower levels of this neurotransmitter, so introducing bacteria that produce GABA into the gut microbiome could offer treatment for these chronic mental health issues Discovering which bacteria produce these neurotransmitters could play an important role in the future of mental health issues, considering that psychiatric illnesses are often comorbid with gastrointestinal problems Similarly, gut dysbiosis could lead to imbalances in neurotransmitters and inflammation or heightened activity of the hypothalamus pituitary-adrenal axis that regulates the stress response Diagnosing and treating gut dysbiosis as the cause of some mental health issues could result in a dramatic increase in quality of life for patients.

Professionals believe a further understanding of the gut microbiome could have a big effect on the future of medicine. Many chronic mental health conditions could, theoretically, be improved, or even cured with the introduction of different microbiota However, there has not been significant research to suggest that introducing microbiota into the gut causes long term changes in the microbiome. In fact, it has been found to only create short term changes In order for treatments to be effective long term, permanent lifestyle changes would have to occur.