Could the Secret to a Good Night's Sleep Be in Your Gut? The Microbiome-Sleep Connection

Oğuzhan Berke Özdil · January 08, 2026 · Sleep Health

Lactobacillus gasseri PSQI gut microbiome insomnia mental health psychobiotics sleep quality

Probiotics and Sleep Quality: What Does the Research Say?

Studies examining the effects of psychobiotics on sleep offer promising results. Some key findings using the PSQI (Pittsburgh Sleep Quality Index), a standard tool for assessing sleep quality, include:

  • In one study, medical students under intense stress were given the Lactobacillus gasseri CP2305 strain for four weeks. The results showed that the group receiving the probiotic demonstrated a significant improvement in global sleep quality compared to the placebo group. This finding is important as it suggests that a specific psychobiotic can support sleep patterns even during stressful periods.

  • On the other hand, it is important to note that not every probiotic has the same effect for everyone. In some probiotic studies, participants have also reported side effects such as "sleep disturbances." This highlights the importance of choosing the right strain and considering individual differences.

How Does It Work? Possible Mechanisms

There are several potential mechanisms underlying how psychobiotics improve sleep quality:

  1. Reduction of Stress Hormones: Chronic stress leads to high cortisol levels. High cortisol makes it difficult to fall asleep and reduces sleep quality. Some psychobiotics, like Lactobacillus gasseri CP2305, have been shown to suppress salivary cortisol release. By mitigating the stress response, they help the body transition into the calm state necessary for sleep.

  2. Regulation of Inflammation: Systemic inflammation in the body can disrupt sleep patterns. Psychobiotics, with their anti-inflammatory effects, can balance this process and create a more restful sleep environment.

  3. Neurotransmitter Production: Gut bacteria contribute to the production of neurotransmitters like serotonin, which plays a role in the sleep-wake cycle. A healthy microbiome supports the balanced production of these important chemicals.

Conclusion

Improving sleep quality is clearly a crucial step toward better mental health, and gut health plays a key role in this equation. But are the effects of the gut-brain axis limited to transient states like mood and sleep?

References

  • Sawada, D., Nishida, K., Kawai, T., Kuwano, Y., Fujiwara, S., & Rokutan, K. (2017). Daily intake of Lactobacillus gasseri CP2305 improves mental, physical, and sleep quality among Japanese medical students enrolled in a cadaver dissection course. Journal of Functional Foods, 31, 188-197.