After analyzing over 40 probiotics across 69 trials, we’ve identified the most promising probiotics for managing mental health-related symptoms in IBS. Our dataset (below) is ordered based on an automated scoring system, which we further refined using additional criteria (below) to select our top choices. Here are the results of our findings. 

Our Top Choice(s)

1. Lactospore (Bacillus coagulans MTCC 5856)
   One small study assessed the effects of Lactospore supplementation in adults with both IBS and major depressive disorder (MDD). (1) This study focused primarily on mental health outcomes and found the following significant improvements:

• Hamilton Rating Scale for Depression (HAM-D): Depression scores dropped from 13.6 to 5.9 (Cohen’s d = 0.92; p = 0.029).
• Montgomery-Asberg Depression Rating Scale (MADRS): Scores improved from 16.3 to 6.0 (Cohen’s d = 0.93; p = 0.031).
• Center for Epidemiological Studies Depression Scale (CES-D): Scores decreased from 19.1 to 8 (Cohen’s d = 0.84; p < 0.01). Other mental health-related parameters, such as the Clinical Global Impression-Improvement (CGI-I), Clinical Global Impression-Severity (CGI-S), Gastrointestinal Discomfort Questionnaire (GI-DQ), and Modified Epworth Sleepiness Scale (mESS), also showed significant improvements (p = 0.01), with the exception of dementia total reaction scoring.

Given these results, Lactospore ranks as our #1 choice for addressing mental health-related symptoms in IBS.

2. I.31
   In one clinical trial, two doses of the probiotic I.31 were tested over six weeks in individuals with IBS-D (diarrhea-predominant IBS). Participants received either a high dose (10-30 billion CFU/day) or a low dose (3-6 billion CFU/day). While neither dose outperformed placebo in terms of overall symptom relief (“global IBS symptoms”), both doses led to improvements in IBS quality of life and reductions in gut-related anxiety, as measured by the IBS-QOL tool. (2) Interestingly, the lower dose (3-6 billion CFU/day) showed a stronger effect size (1.00) compared to the higher dose (0.42). However, it’s important to note that the effect size for the higher dose was not statistically significant. These findings suggest that the lower dose may offer a more robust clinical response. As a result, I.31 secured its position as our #2 choice for mental health-related symptom relief in IBS. (2)

Our Criteria 

The probiotics in our full database (below) are automatically ranked based on their 1) effect size for mental health-related symptoms, followed by 2) effect size for overall IBS symptoms (‘Global IBS Symptoms’), and finally by 3) the quality of evidence from the studies.

For this summary, we selected our top choices based on these rankings, along with the following additional criteria:

• Evidence Quality Score: We only included probiotics backed by studies with an evidence quality score of 75% or higher.
• Effect Size: Only probiotics that demonstrated a moderate to high effect size (>0.5) for mental health-related symptoms made the cut.
• Clear Dosing Information: Only probiotics with clear and reliable dosing data were included.
• Commercial Availability: Probiotics needed to be commercially available to consumers.

No Direct Comparisons
It’s important to note that there are no direct comparisons between the probiotics in our database based on identical study methods. Therefore, we cannot definitively rank one probiotic as superior to another. Both Lactospore and I.31 have demonstrated potential for improving mental health-related symptoms in IBS. However, it’s crucial to remember that probiotics should never replace established mental health treatments or medications. Any probiotic or supplement used alongside conventional IBS or MDD treatment should always be discussed with your healthcare provider.

*Population values represent the per protocol population size from studies specifically assessing the above parameters.

*Effect sizes are reported as the weighted mean effect size across studies.

References

1. Majeed M, Nagabhushanam K, Arumugam S, Majeed S, Ali F. Bacillus coagulans MTCC 5856 for the management of major depression with irritable bowel syndrome: a randomised, double-blind, placebo controlled, multi-centre, pilot clinical study. Food Nutr Res. 2018 Jul 4;62. doi: 10.29219/fnr.v62.1218. PMID: 29997457; PMCID: PMC6034030. 
2. Lorenzo-Zúñiga V, Llop E, Suárez C, et al.  I.31, a new combination of probiotics, improves irritable bowel syndrome-related quality of life.  World J Gastroenterol 2014; 20(26): 8709–8716. [doi 10.3748/wjg.v20.i26.870] 

When selecting our top probiotic picks, we ensure they are commercially available and backed by high-quality evidence, with an average score above 75% for the relevant symptom parameters. The probiotics must also demonstrate a moderate to high effect size (>0.5) for these symptoms. If there are more than five candidates, we limit our top picks to the best five based on the effect size for relevant symptoms and Global IBS symptoms, as well as evidence quality. This ensures our recommendations are practical and reliable.

When selecting our top probiotic picks, we ensure they are commercially available and backed by high-quality evidence, with an average score above 75% for the relevant symptom parameters. The probiotics must also demonstrate a moderate to high effect size (>0.5) for these symptoms. If there are more than five candidates, we limit our top picks to the best five based on the effect size for relevant symptoms and Global IBS symptoms, as well as evidence quality. This ensures our recommendations are practical and reliable.