From mouse to people: How gut bacteria affects mental health


It has been proposed that gut bacteria, or microbes, have an effect on a person’s mental health. A growing body of research has reinforced the truth behind this theory. Studies on the effects of gut bacteria started with mice and gradually moved on to human beings to observe how probiotics affected their gut bacteria and, subsequently, their mental and physical health.

In a 2013 study in Canada, researchers observed how intestinal microbes influenced the brain in mice. They carried out an experiment in which “germ-free” (kept in sanitized conditions) mice and normal mice were kept in a dark box with access to well-lit areas to see how much time they spent exploring outside the box of their own volition. If was found that the germ-free mice spent more time outside the box and explored high ledges, both behaviors indicated that they were less anxious. This is was confirmed further when the normal mice were given antibiotics, which resulted in their exhibiting less cautious behavior while they also had an increase in a molecule linked to lower depression and anxiety.

Another study in 2013 from the California Institute of Technology in Pasadena examined mice with some features of autism. These mice had lower levels of the gut bacterium, Bacteroides fragilis (B. fragilis) and were also stressed, antisocial and exhibited gastrointestinal symptoms that were common with autism. When the scientists fed the mice B. fragilis they observed that these symptoms were reversed.

Expanding these studies, scientists have also worked with human beings to observe how prebiotics and probiotics affect their mental health. One study in France in 2011 found that those study participants who took probiotics for 30 days had reduced levels of psychological distress. To follow that, a 2013 study at the University of California, Los Angeles gave women milk with and without probiotics and scanned their brains while they viewed photos of people with emotional facial expressions. This study found that those women who had taken the probiotics had less brain activity in the areas involved with processing emotions. Lastly, a study in England examined 45 healthy individuals aged 18 to 45, giving them either a prebiotic or a placebo daily for three weeks. Participants completed several computer tests assessing how they processed emotional information such as negative and positive words. Researchers discovered that those participants who took the prebiotic paid less attention to the negative information and more attention to the positive information than those participants who took the placebo. The results were similar to those individuals who take medication for depression and/or anxiety, thus suggesting that those participants who took the prebiotics had less anxiety.

These types of studies demonstrate that microbes can affect mental health, although scientists still need to determine why. More research is also needed to determine whether or not gut bacteria play a role in major psychiatric conditions and, if so, which bacteria are important.

White River Academy provides treatment programs for those teens struggling with psychiatric disorders. If your teen is in need of help for a mental health disorder, addiction or co-occurring conditions please call at 866-520-0905 to find out more about our programs.

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