Dr. Ahmed A good night’s sleep often feels like the simplest prescription for better health, yet millions of people worldwide struggle with insomnia. Now, new research suggests that the answer to sleepless nights might lie deep in the gut.
A study published in General Psychiatry has found evidence that the connection between the gut and the brain is a two-way street.
Not only can the gut microbiome, the diverse community of bacteria living in our digestive tract, shape sleep quality, but insomnia itself may alter the composition of those microbes.
A gut–brain conversation
For years, scientists have spoken of the “gut-brain axis,” the complex communication network that links digestion, metabolism, mood, and cognition to the trillions of microorganisms in the intestine.
Previous studies hinted that gut imbalances might influence sleep and that poor sleep could disrupt gut health. But what has remained unclear is whether these links are causal associations or true cause-and-effect relationships.
The new study takes a step closer to answering that question. Using large genetic datasets, the researchers applied a technique called Mendelian randomisation, a method that uses genetic variants as natural experiments to explore causality.
In essence, it allowed them to ask: if someone has a genetic tendency toward higher levels of certain gut bacteria, does that also increase their risk of insomnia? And conversely, do genes linked to insomnia predict differences in gut bacteria?
What the researchers found
The team analysed data from nearly 400,000 people on insomnia traits and more than 26,000 participants who had undergone gut microbiome profiling.
The results were striking: several bacterial groups appeared to influence the risk of developing insomnia, while insomnia itself was linked to measurable shifts in the gut microbial landscape.
In fact, the study identified over a dozen bacterial taxa associated with increased insomnia risk and nearly as many linked to a reduced risk.
Some bacteria seemed protective, while others appeared to make people more vulnerable.
The researchers also found evidence that living with insomnia may lead to significant changes in gut composition, decreasing some bacteria while encouraging the growth of others.
One bacterial genus, Odoribacter, stood out as especially significant in influencing insomnia. While its exact role is not fully understood, the finding highlights how individual microbes might play outsized roles in sleep regulation.
Why this matters
Insomnia is one of the most common sleep disorders worldwide. It not only drains energy and affects daytime performance but also increases the risk of depression, anxiety, diabetes, and cardiovascular disease.
Despite its prevalence, treatment options remain limited and often involve medications with side effects or behavioral therapies that require sustained effort.
The idea that gut microbes may influence sleep opens the door to new possibilities. If certain bacteria can increase or decrease insomnia risk, targeted interventions, through diet, probiotics, or even fecal microbiota transplantation, could eventually become part of sleep medicine.
“Sleep and gut health may not be separate issues at all,” the study’s authors wrote. “Instead, they may form part of a dynamic feedback loop, where improving one could also help restore the other.”
A two-way relationship
Perhaps the most important finding from this research is that the link runs in both directions. Insomnia does not just result from gut imbalances; it may actively reshape the microbial environment.
This reciprocal relationship means that a vicious cycle could form: disrupted sleep changes gut bacteria, and altered gut bacteria worsen sleep.
Breaking this cycle may be key. Interventions that address both sleep hygiene and gut health simultaneously might prove more effective than treating either in isolation.
The authors themselves noted several limitations. All participants were of European descent, so the results may not apply universally.
Gut microbiomes vary widely across cultures, diets, and lifestyles. Moreover, Mendelian randomisation provides evidence of likely causality but does not substitute for direct clinical testing.
Still, the work adds important weight to a growing body of science connecting sleep and the gut.
‘Our results suggest that the relationship between gut microbiota and insomnia is likely to be bidirectional, meaning that changes in gut microbiota may increase the risk of insomnia and that insomnia may in turn alter the composition of gut microbiota,’ said researchers in a press release [ref]
What’s next for patients
For now, the practical takeaway is that caring for gut health may indirectly support better sleep. Diets rich in fiber, fermented foods, and plant diversity are known to nurture beneficial bacteria.
Regular sleep routines, stress management, and exercise also support both the microbiome and healthy sleep.
This does not mean probiotics or diet changes are proven cures for insomnia, but they may form part of a broader approach.
In the future, doctors could prescribe microbiome-targeted therapies alongside traditional sleep treatments, creating a more holistic strategy.
Looking ahead
The study marks an exciting new chapter in sleep science. For decades, insomnia research has focused mainly on the brain, neurotransmitters, hormones, and circadian rhythms. Now, the gut is emerging as a key player.
If future trials confirm these findings, we may see a shift in how insomnia is managed. Instead of prescribing only sleeping pills or behavioral therapy, clinicians could one day also consider microbiome health, testing patients’ gut bacteria, and tailoring interventions accordingly.
The research also reinforces the idea that our health systems should not treat the body’s organs in isolation. The brain, gut, and immune system constantly interact, shaping everything from mood to metabolism to sleep.
The bottom line
Insomnia is not just “in your head”; it may also be in your gut. This new study provides some of the strongest evidence yet that sleep and the microbiome are deeply intertwined.
While more work is needed, the message is clear: the path to better sleep may start with nurturing the trillions of microbes within us.
As the science develops, one thing is certain: sleep medicine and microbiome research are no longer separate fields, but partners in uncovering how the smallest organisms in our body may shape one of our most vital needs: a good night’s rest.
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