Research shows that the probiotic Lactiplantibacillus plantarum SG5 reduced anxiety and insomnia severity in college students compared with a placebo. In this 2026 randomized trial of 113 students, the probiotic group had lower anxiety scores (12.00 versus 16.50) and lower insomnia scores (8.00 versus 11.00). According to research reviewed by Gram, it also shifted gut bacteria.
According to research reviewed by Gram, a probiotic strain called Lactiplantibacillus plantarum SG5 may help college students who struggle with anxiety and poor sleep. In this randomized controlled trial, 113 students took either the probiotic or a placebo pill. Students taking the probiotic reported lower anxiety scores and less severe insomnia than students taking the placebo. Researchers also observed shifts in gut bacteria, including higher levels of Bifidobacterium and Lactobacillus and lower levels of Bacteroides and Prevotella. These results point toward a possible link between the gut and the brain, since the two communicate closely. The findings are promising, but they come from a single study. Larger and longer trials are needed before this strain can be considered a proven remedy for anxiety or insomnia.
Key Statistics
A 2026 randomized controlled trial of 113 college students found that the probiotic Lactiplantibacillus plantarum SG5 lowered anxiety scores to an average of 12.00, compared with 16.50 in the placebo group.
In the same 2026 trial, students taking the probiotic had an average insomnia severity score of 8.00 on the Athens Insomnia Scale, compared with 11.00 for those taking a placebo.
A 2026 gut microbiota analysis of 35 students per group found that Bifidobacterium and Lactobacillus increased after probiotic use, while Bacteroides and Prevotella decreased.
The Quick Take
- What they studied: Researchers wanted to know whether a specific probiotic, a beneficial live bacteria strain, could reduce anxiety and insomnia in college students and whether it changed the bacteria living in their digestive systems.
- Who participated: 113 college students completed the study. Fifty-six took a placebo, which is a pill with no active ingredient, and 57 took the probiotic. A smaller group of 35 students in each group also provided stool samples so researchers could study their gut bacteria.
- Key finding: Students who took the probiotic had lower anxiety scores than the placebo group, with average scores of 12.00 compared to 16.50 on the anxiety scale. Their insomnia scores were also lower, at 8.00 compared to 11.00. These differences were statistically significant, meaning they were unlikely to be due to chance alone.
- What it means for you: If you struggle with stress or poor sleep, this research offers a hopeful lead, but it is not yet a reason to start a specific supplement. Talk with a doctor or campus health professional before trying a probiotic for anxiety or insomnia, especially if your symptoms are severe or ongoing.
The Research Details
This was a clinical trial in which students were divided into two groups. One group received the probiotic L. plantarum SG5, and the other received a placebo that looked the same but contained no active bacteria. Neither the students nor the research team were expected to know which pill each person took until the study ended, which helps prevent bias in how results are judged.
At the start and end of the study, students completed standard questionnaires. The Hamilton Anxiety Scale measured anxiety symptoms, and the Athens Insomnia Scale measured how much sleep problems affected daily life. Higher scores indicate more severe symptoms.
To see whether the probiotic changed the gut, researchers collected stool samples from a subset of students after the intervention and used high-throughput sequencing, a method that identifies and counts many types of bacteria at once. This allowed them to compare the overall mix of gut microbes and the amounts of specific bacterial groups between the two groups.
A randomized, placebo-controlled design is one of the strongest ways to test whether a treatment works. Because participants were randomly assigned to groups, differences between the groups are more likely to come from the probiotic itself rather than from other factors such as age, habits, or expectations. The placebo comparison also helps separate real effects from the power of simply taking a pill.
The study was registered in a public clinical trial database (ChiCTR2400083149), which means the plan was recorded before or during the trial. This helps reduce concerns that researchers changed their goals after seeing the results. The study also reports statistical significance for its main findings. However, the gut microbiome results involved only 35 students per group, which is a fairly small sample. The paper was published in a peer-reviewed journal, which means outside experts reviewed it before publication.
What the Results Show
The main finding was that students taking L. plantarum SG5 reported less anxiety than students taking the placebo. On the Hamilton Anxiety Scale, the placebo group averaged 16.50, while the probiotic group averaged 12.00. The difference was statistically significant, with a p-value of 0.0011, meaning there is a very low chance this result happened by accident.
Sleep quality also improved more in the probiotic group. On the Athens Insomnia Scale, the placebo group averaged 11.00 and the probiotic group averaged 8.00. This difference was even stronger statistically, with a p-value below 0.0001. In practical terms, the probiotic group had fewer and milder sleep problems by the end of the study.
The gut bacteria results showed that the probiotic changed the community of microbes living in participants’ intestines. Overall microbial diversity decreased in the probiotic group. Bifidobacterium and Lactobacillus, two bacterial groups often considered beneficial, increased. Bacteroides and Prevotella, two other groups, decreased. Researchers did not claim these bacterial shifts directly caused the improvements in mood or sleep, but they suggest the gut may be part of the mechanism.
The changes in gut bacteria were the study’s most distinctive secondary result. The increase in Bifidobacterium and Lactobacillus is notable because these groups are commonly studied for their roles in digestion and immune health. The decrease in overall diversity is a change that researchers must interpret carefully, since a more varied gut community is often associated with good health, although the meaning of a short-term drop in diversity after a probiotic is still not fully understood.
The researchers framed these microbial changes as a possible pathway connecting gut health to mental health. This idea, often called the gut-brain axis, proposes that bacteria in the digestive system can send signals to the brain through nerves, the immune system, and chemical messengers. The gut bacteria data support this idea as a hypothesis, but they do not prove it on their own.
Previous research on probiotics and mental health has been encouraging but mixed. Some trials in adults and young people have reported improvements in stress, low mood, or sleep, while others found little or no benefit. Many earlier studies focused on general mood or on people with specific medical conditions, so this trial adds useful information about a specific group, college students, who often face high academic pressure and irregular sleep. The idea that gut bacteria influence brain health has been studied extensively in animal research, and this human trial moves that idea a step closer to everyday use, though more human trials are still needed.
The study included only college students, so the results may not apply to other age groups or to people with serious anxiety or insomnia disorders. The gut bacteria analysis involved just 35 students per group, which limits how strongly researchers can draw conclusions about the microbiome. The findings also come from one trial, and repeating the study in different settings is important before drawing firm conclusions. Anxiety and sleep were measured with questionnaires, which depend on how people judge and report their own symptoms. The published summary does not clearly describe how long the probiotic was taken, how long the effects lasted after stopping, or whether any side effects were reported in detail. Finally, the study did not show that the changes in gut bacteria caused the improvements in anxiety and sleep.
The Bottom Line
Moderate confidence: The trial suggests that L. plantarum SG5 may help reduce anxiety and insomnia symptoms in college students. Because this is one promising study, the evidence is encouraging but not yet strong enough to recommend the probiotic as a standard treatment. Anyone considering it should consult a healthcare provider, particularly if they take other medications or have a diagnosed mental health condition. Lifestyle habits with strong evidence, such as regular sleep schedules, physical activity, and stress management, remain important foundations for both anxiety and sleep.
Students dealing with mild to moderate stress or trouble sleeping, and health professionals who follow research on probiotics and mental health, may find these results most relevant. People with severe anxiety, clinical insomnia, depression, or other serious conditions should not rely on a probiotic alone and should seek professional care. Children, pregnant people, and people with weakened immune systems should speak with a doctor before starting any probiotic. People who do not experience anxiety or sleep problems will not likely see a benefit from this research.
The study measured outcomes over the course of the trial, but the exact duration is not clearly stated in the summary. Many people who try probiotics notice changes within several weeks, though gut bacteria typically take time to shift and results vary from person to person. Anyone who tries a probiotic should give it a reasonable trial period, such as several weeks, and track changes in sleep and mood before deciding whether it is helpful.
Frequently Asked Questions
Can a probiotic help with anxiety and sleep problems in college students?
A 2026 randomized trial of 113 college students found that the probiotic Lactiplantibacillus plantarum SG5 was linked to lower anxiety and insomnia scores than a placebo. The results are promising, but they come from a single study, so more research is needed before it can be considered a proven treatment.
What is Lactiplantibacillus plantarum SG5?
Lactiplantibacillus plantarum SG5 is a strain of beneficial bacteria, a type of probiotic, that was tested in a 2026 clinical trial. It is one specific strain, so results from other probiotics may differ and should not be assumed to apply.
How does gut bacteria affect anxiety and sleep?
Researchers believe the gut and brain communicate through nerves, the immune system, and chemical messengers, a connection called the gut-brain axis. In a 2026 trial, a probiotic changed gut bacteria in 35 students per group, but the study did not prove that these changes caused the improvements in mood or sleep.
Should I take a probiotic if I have trouble sleeping or feel anxious?
Talk with a doctor or healthcare provider before starting a probiotic, especially if you have a diagnosed condition or take medications. Sleep habits and stress management have strong evidence behind them, and a probiotic should not replace professional care for serious anxiety or insomnia.
Want to Apply This Research?
- Track your nightly sleep quality on a simple 0 to 10 scale each morning, and record how many minutes it took you to fall asleep. Once a week, rate your anxiety on a 0 to 10 scale and note any major stressors. Comparing these numbers over four to eight weeks can show whether changes are happening.
- Set a consistent daily reminder to take your supplement at the same time each day, and pair it with a short wind-down routine, such as dimming screens 30 minutes before bed. Log both the supplement and the wind-down routine in the app so you can see patterns between habits and symptoms.
- Review your tracked data monthly to look for trends in sleep and anxiety scores. If scores have not improved after two to three months, or if symptoms worsen, discuss next steps with a healthcare provider. Keep a record of any digestive changes, side effects, or medications so you can share a complete picture at your next appointment.
This article summarizes a single clinical trial and is for general information only. It is not medical advice and does not replace consultation with a qualified healthcare provider. Probiotic effects can vary between people and between products, and the findings may not apply to everyone, particularly those with serious anxiety, depression, or chronic sleep disorders. Always speak with a doctor before starting a new supplement, especially if you are pregnant, nursing, have a weakened immune system, or take other medications.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.