The Microbiome, Anxiety, and Early Life Adversity


Our minds and our guts are closely connected. The gut’s microbiome, a community of microorganisms including bacteria, viruses, and fungi that live in the digestive system, synthesises many of the neurotransmitters (hormones) that regulate our mood, stress, and sleep. A healthy microbiome is linked to better mental health, a stronger immune system, and better digestion.

Equally, mental health disorders and gastrointestinal disorders (disorders of the main passage of the digestive system) often co-occur. Both anxiety and early life adversity are associated with gastrointestinal disorders and changes in the gut microbiome community.

Research also suggests that differences in microbiome bacteria may play a role in the development of PTSD (post-traumatic stress disorder) after traumatic events.

What Is the Gut Microbiome?

The gut microbiome is made up of trillions of bacteria, viruses, and fungi. These bacteria are essential for both physical and mental health, helping to digest food and communicate with the immune system to respond to infections.

They also play a vital role in the functions of the brain and central nervous system, producing chemical signals (hormones) that communicate between different cells in the body and affecting hormonal and nervous systems associated with stress responses, anxiety, and memory.

A diverse community of gut microbes is associated with good health. But on average, humans living in cities and urban settings have a less diverse microbiome than they did previously.

This may prevent immune systems from functioning effectively, make anxiety and depression more likely, and affect the digestion of food.

How Is Gut Health Related to Anxiety?

Research shows that anxiety could be five times as likely in people with irritable bowel syndrome (IBS), a type of disorder of the digestive system). Equally, people with IBS could be four times as likely to live with anxiety.

In some cases, IBS may precede anxiety conditions, while in others, anxiety conditions may come first. Psychological stress may also make IBS symptoms worse. Experts suggest that there may be a two-way relationship between anxiety and IBS, where each condition may exacerbate the other.

How Do Trauma and Early Life Adversity Affect Gut Health?

Young people who face early life adversity (difficult events in the first years of childhood) are much more likely to develop gastrointestinal disorders than those who don’t.

Some research shows that adults with adverse childhood experiences, such as a family member with mental illness or emotional abuse, are twice as likely to develop IBS symptoms. 

Early life adversity also affects how certain areas of the brain develop and impacts the thinking skills and emotions connected with those regions. Many of these regions also look different in adults living with IBS, underlining the links between the mind and the gut.

A study among 344 young people (3-18 year olds) found that those who had adverse care experiences (in institutional or foster homes) had more gastrointestinal symptoms than those raised by their biological parents. Gastrointestinal symptoms were also associated with current and future anxiety. 

Scientists still aren’t sure exactly what pathways explain the connection between early life adversity, anxiety, and gastrointestinal health. However, the microbiome in the gut may play an important role.

These microorganisms influence immune pathways that are directly connected with anxiety. What’s more, research has shown that changing the makeup of gut bacteria can affect anxiety levels in humans. 

At the same time, a young person’s social and psychological environment affects the way the microbiome develops during certain developmental stages.

Like the brain, the microbiome seems particularly vulnerable to external effects during the first four years of a child’s life. Stressful or traumatic events during this time may have a significant impact on the growth of a healthy, diverse gut microbiome. 

In the previously mentioned study, young people who had experienced diversity showed changes in the diversity of gut microbes, while gut bacteria levels were linked to the way a young person’s brain reacted to emotional faces.

Among rodents, probiotic treatments that improve the health of the gut microbiome have been shown to reverse the effects of early-life adversity on certain behaviours and parts of the brain.

These findings suggest that improving microbiome health may help to treat anxiety in people who have lived through adverse childhood experiences.

How Might Gut Bacteria Affect the Development of PTSD?

Post-traumatic stress disorder (PTSD) develops in about 20% of individuals who experience a traumatic event. Research shows that people with PTSD tend to experience dysfunctions in their immune and inflammatory systems, producing abnormal reactions to stress. These changes may play a role in why some people develop PTSD, and others do not.

For example, someone whose early life experiences have caused changes in these systems may be more likely to develop PTSD symptoms after a later traumatic event.

Some experts think that unbalanced gut microbiota in early life may have long-lasting effects on the immune system that make people more vulnerable to the development of PTSD after experiencing trauma or even contribute to the disorder itself.

This means that it may be possible to prevent or even treat PTSD by adapting gut bacteria through probiotics that improve microbiome diversity or add specific bacteria to the microbiome.

While relatively unexplored, these possibilities may be exciting developments in the treatment of trauma and other mental health disorders.

The Wave Clinic: Making a Difference in Young People’s Lives

The Wave Clinic offers top-tier mental health support for young people, setting the global standard for youth mental healthcare.

Our specialist programs offer a whole-person approach that combines clinical care with education, experiences, and social responsibility, building life advantages for teenagers and young adults from around the globe. 

Our seven core elements of treatment emphasise medical and psychological support, inspiring adventures, skills development, and inner healing.

We understand the impact of trauma on the way a young person relates to themselves and the world around them, sensitively addressing past experiences to allow safe and holistic recovery. 

If you’re interested in our programs, get in touch today.

Fiona - The Wave Clinic

Fiona Yassin is the founder and clinical director at The Wave Clinic. She is a U.K. and International registered Psychotherapist and Accredited Clinical Supervisor (U.K. and UNCG).

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