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How Probiotics Affect Sleep and Insomnia (Research Summary)

by Dale Cudmore | Updated: Jan 24, 2023

A lot of modern research is exploring how gut health can affect our health in other ways.

While it’s still early, there seems to be a link between gut health and mental disorders, obesity, heart health, and even insomnia (1).

For many people, probiotics (which are just certain bacteria species) are a convenient way to populate their gut with bacteria that they may be lacking.

This is a complex topic, but I’ve done my best to simplify and summarize current research here.

Understanding The Brain-Gut Axis

The first thing you need to understand is the brain-gut axis, which is the subject of a lot of research these days.

The brain-gut axis essentially explains how changes in the gut microbiome (i.e. species and amount of gut bacteria) can directly affect brain function (2,3,4).

In short, gut bacteria can communicate with the central nervous system (CNS) through 3 pathways:

  1. Neural
  2. Endocrine (hormones)
  3. Immune

The image below shows a high-level overview of this process (1).

Some potential interactions can affect sleep. For example, serotonin production is greatly influenced by the gut microbiome, and serotonin is one of the key hormones involved in sleep regulation (5).

Microbial metabolism is also involved in producing several key neurotransmitters that are key to good sleep including dopamine and GABA (6).

SummaryIn plain English, having poor gut health can directly lead to neural disorders (i.e. mood, depression, insomnia), hormone imbalances, or a poor immune system.

How Probiotics Might Help Improve CNS Related Disorders

All this begs an obvious question: can we improve gut health in order to treat certain conditions?

Early research looks promising.

One review looked at a variety of animal and human studies that involved giving subjects commercially available probiotics (7). They found:

These probiotics showed efficacy in improving psychiatric disorder-related behaviors including anxiety, depression, autism spectrum disorder (ASD), obsessive-compulsive disorder, and memory abilities, including spatial and non-spatial memory.

So while there are a lot of specifics to work out, probiotics may be a tool to improve gut health and help treat certain conditions.

Can Probiotics Cause Insomnia?

In general, probiotics will likely improve mental and physical health, if anything.

With that being said, research doesn’t show much (if any) benefit from an already healthy person taking probiotics. While they’re generally “safe,” there can be unexpected bacteria-host interactions that actually cause health problems, potentially something like insomnia (8).

There are some cases where patients are treated successfully with antibiotics (which kill certain bacteria) instead of adding more through probiotics. One study with subjects who had chronic fatigue syndrome found (9):

When patients were treated with antibiotics to relieve the imbalance in the intestinal microbiota, actigraphy records revealed that sleep efficiency, sleep time, and mood were improved

Finally, there may be negative consequences of having too many probiotics.

SummaryHowever, this isn’t a topic that’s been studied very much from what I’ve found, and there’s nothing directly linking probiotics to insomnia. So while I wouldn’t say it’s impossible, it’s not the most likely issue to run into.

Can Probiotics Improve Insomnia Symptoms?

Insomnia often comes with other health problems.

There are many causes of it, and a strong link between insomnia and conditions like depression, anxiety disorders, and even irritable bowel syndrome (10).

I’ve chosen to summarize the main ways that insomnia could be affected by probiotics and gut health.

Sleep Hormone Production

How tired someone is, and how well they sleep is largely governed by hormones like serotonin, cortisol, and melatonin.

Through the brain-gut axis, gut bacteria can directly influence the production of these hormones (11). Too much or not enough of one at a certain time can lead to daytime sleepiness or insomnia.

This relationship goes both ways.

Research has shown that people with circadian rhythm disorders (often developed through shift work) can negatively affect gut health, which then in turn can cause further issues (12).

One proposed treatment approach is to use probiotics or antibiotics (depending on the case), alongside dietary adjustments to limit the damage that a circadian rhythm disorder has on overall health.

Stress and Insomnia

Stress is one of the leading causes of insomnia, particularly sudden (acute) insomnia, and depression (13).

Studies have shown that stress negatively affects the gut microbiome (14). It’s not surprising that some research shows that some probiotics may improve stress response and exert an anti-anxiety effect (15).

Depression and Insomnia

Depression and insomnia are strongly linked together.

Many people with insomnia develop depression, and many people with depression develop insomnia (16). Research has shown that insomnia increases the severity of depression over time (17).

At this time, no single hypothesis has been able to explain this complex relationship.

There are some theories, one of which is that the brain-gut axis plays a major role:

  • Both Lactobacillus and Bifidobacterium secrete GABA. Since an abnormal expression of GABA is common in patients with depression and insomnia, gut health is involved to some degree (18).
  • Research that changes the composition of the intestinal microbiome through the use of antibiotics or probiotics have been shown to cause or alter anxiety or depression-like symptoms (19,20). So probiotics are potentially a double-edged sword that could make problems better or worse.
  • Stress can alter gut composition, which could explain how stress often causes both depressive and insomnia symptoms.

Keep in mind that this is largely speculation at this point, but there does appear to be a connection between the gut microbiome and conditions like insomnia and depression.

Summary: Do Probiotics Improve or Worsen Sleep Quality?

For now, we know that the intestinal microbiota (gut bacteria) plays some role in many psychiatric disorders including depression.

However, this research is incomplete.

While most theories look at the possibility of probiotics improving gut health and in turn improving sleep quality, it’s also possible that probiotics could worsen sleep quality (especially in people with already healthy diets and gut microbiomes).

I know that’s not the most satisfying answer, but hopefully this topic will be better understood in the years to come.

For now, know that it does seem possible for probiotics to improve sleep in some, and even trigger insomnia symptoms in others. For any specific testing and diagnosis, you’ll need to see a doctor.


  1. The Role of Microbiome in Insomnia, Circadian Disturbance and Depression
  2. Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour
  3. Normal gut microbiota modulates brain development and behavior
  4. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders
  5. Action of serotonin on the gastrointestinal tract
  6. Gut-Microbiota-Brain Axis and Its Effect on Neuropsychiatric Disorders With Suspected Immune Dysregulation
  7. Effect of Probiotics on Central Nervous System Functions in Animals and Humans: A Systematic Review
  8. Probiotic use in clinical practice: what are the risks?
  9. Sleep quality and the treatment of intestinal microbiota imbalance in Chronic Fatigue Syndrome: A pilot study
  10. Irritable bowel syndrome: new and emerging treatments
  11. Ultrastructural evidence for communication between intramuscular vagal mechanoreceptors and interstitial cells of Cajal in the rat fundus
  12. Rhythmicity of the intestinal microbiota is regulated by gender and the host circadian clock
  13. The Microbiome in Mental Health: Potential Contribution of Gut Microbiota in Disease and Pharmacotherapy Management
  14. Acute stress-induced hypersensitivity to colonic distension depends upon increase in paracellular permeability: role of myosin light chain kinase
  15. Evidence of the Anti-Inflammatory Effects of Probiotics and Synbiotics in Intestinal Chronic Diseases
  16. Sleep disturbance among people with major depressive disorders (MDD) in Singapore
  17. Risk of psychiatric disorders in patients with chronic insomnia
  18. γ-Aminobutyric acid production by culturable bacteria from the human intestine
  19. Targeting the Microbiota-Gut-Brain Axis: Prebiotics
  20. Antidepressants, antimicrobials or both

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.