Gut bacteria can cause insomnia (and a fecal transplant could fix it)

48% of Spanish adults lack quality sleep , and 54% sleep less than the recommended number of hours . Furthermore, one in three Spanish adults wake up feeling like they haven't had a restful night's sleep. This is according to the latest data published by the Spanish Society of Neurology .

On the other hand, problems with intestinal dysbiosis , also known as microbiota imbalance , are commonplace. There is still no reliable global figure due to the lack of a single clinical criterion, which means that estimates of affected patients depend heavily on the index used.

There are already studies linking microbiota alterations with insomnia . Now, a new study, published this Wednesday in the journal General Psychiatry , reaffirms the links between the two conditions.

The research team explains to this newspaper that, although several previous studies have explored the effects of the gut microbiome , it was unclear how the groups of bacteria housed in the gut could contribute to the risk of insomnia . "The bacteria involved are numerous, and traditional studies have focused on associations between microbiota diversity and the disorder, but have struggled to establish whether these connections are causal," explains Shi Shang Yun, one of the lead authors.

“ Certain types of bacteria appear to increase or decrease the risk of sleep disorders, while insomnia itself appears to alter the abundance of some of them,” the paper states.

The authors, who are from the Department of Psychiatry at the Cerebral Hospital of Nanjing Medical University in China, used Mendelian randomization, a method that uses genetic variation to estimate the causal effect of an exposure factor on a health outcome.

They based their work on data from 386,533 European people with insomnia, taking into account a previously published genome-wide analysis , gut microbiome data from 18,340 people from the MiBioGen alliance, and information from 8,208 participants in the Dutch Microbiome Project. "The composition of the microbiome varies across ethnicities and geographic regions," they note, referring to the limitations of the study.

The Odoribacter bacteria genus was significantly associated with the risk of suffering from this sleep disorder.

The results reveal that the Odoribacter bacteria genus is "significantly" related to the risk of suffering from this sleep disorder. Yun describes that, by identifying 41 causal bacterial groups and their diverse impacts, they were able to delve deeper into how the gut-brain axis regulates sleep.

The researchers also highlight that future therapies could include the use of probiotics , prebiotics, or fecal microbiota transplants, with the goal of improving patient care. "This lays the groundwork for targeted microbiome-based interventions, offering new potential for preventing or treating insomnia using other approaches," Yun adds.

He also insists that understanding how different gut bacteria affect insomnia risk is crucial : "There are some species that are more important and others that are less so, and discovering this shows another avenue for intervention."

"Understanding their mechanisms, such as metabolic byproducts , neurotransmitter regulation, or immune signaling, turns causal relationships into practical information," he concludes.