A new clinical study by a group of French scientists has found an interesting connection between depression, chronic stress, gut bacteria, and the body’s endocannabinoid system.

Depression and gut?

Scientists are studying the link between depression and the gut instead of the brain. There are many theories about how gut bacteria is connected to depression, but researchers are still trying to understand precisely how it works.  A new study published in this month’s Nature Communications journal highlighted how gut bacteria imbalances can disrupt the body’s endocannabinoid system, leading to depression. 

During the 1990s, researchers from Israel conducted a study on the effects of cannabis and made a significant discovery. They discovered that the human body has a built-in network of cannabinoid receptors. This natural network, the endocannabinoid system or ECS, is one of the body’s most critical regulatory systems, keeping immune responses, learning, sleep, and appetite in balance. 

Researchers hypothesise that disturbances in the human body’s system for regulating stress and emotion can lead to mood disorders, fibromyalgia, migraines, and irritable bowel syndrome.

The researchers conducted a study to compare the gut bacteria of healthy mice with those exhibiting symptoms of depression. To induce depressive symptoms, the study authors exposed a group of mice to unpredictable chronic mild stress (UCMS), which has been proven to cause depressive behaviours like anxiety and loss of appetite in mice. 

The levels of gut bacteria in the depressed mice differed from those in the control group, confirming the researchers’ expectations. To further investigate their hypothesis, the researchers transferred faecal matter from the intestines of the depressed mice to the healthy mice. This process involves moving the entire gut microbiome of one animal to another. The researchers found that the healthy mice began showing signs of depression after receiving these transplants.

Surprisingly, transferring the microbiota from an animal with mood disorders to a healthy animal can result in biochemical changes and cause depressive-like behaviours in the latter. 

According to researchers, prolonged stress can alter the gut microbiome and lower the production of endocannabinoids. This decrease in endocannabinoids can result in reduced hippocampus activity, which recent studies have linked to memory loss and depression. 

“This might be the pathway, at least in part, that links microbiota dysbiosis to mood disorders, which in turn, may affect the composition of the gut microbiota through physiological adjustments and modulation of the immune system,” the study explains.

This study examined the connection between gut microbiota dysbiosis and depressive-like states. Depression is often linked to chronic stress, and animal models of depression usually involve chronic stress or manipulation of stress-sensitive brain circuits. The study utilised a mouse model of depression called UCMS and discovered that when microbiota from these mice was transplanted to other mice, it reduced adult hippocampal neurogenesis and resulted in depressive-like behaviours.

During the last phase of the investigation, the scientists uncovered a straightforward method to assist the mice in defeating their depression using bacteria. By introducing a specific type of Lactobacilli bacteria, the researchers observed an escalation in the endocannabinoid levels of the animals. This, in turn, led to the eventual vanishing of the depressive symptoms.

The present study notes that natural cannabis “improves mood in humans,” likely because plant-based cannabinoids like THC can bond to the body’s natural endocannabinoid receptors. The authors also note that low doses of synthetically-produced cannabinoids can “produce anxiolytic- and antidepressant-like effects in animal models.” 

The research study sheds light on the endocannabinoid system’s impact on mood disorders, particularly depression. While the study does not delve into the practical implications of utilising natural cannabinoids to treat depression, it does offer invaluable information regarding the ECS’s role in mood disorders. Future research studies could pave the way for innovative cannabis-based treatments to restore balance to the ECS and alleviate the negative effects of depression or other mood disorders. Such therapies could enhance the quality of life for those with mood disorders.

Link to the research:
The effect of gut microbiota on depressive-like behaviours in mice is mediated by the endocannabinoid system.
more research on the subject: Gut bacteria linked to endocannabinoid levels and depression

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