Benefits
Overall distress and cortisol in healthy volunteers
In a 30-day double-blind, placebo-controlled trial in healthy volunteers taking 3 billion CFU daily, scores improved on the overall distress index and on the somatization, depression and anger-hostility scales, the HADS global score improved, and 24-hour urinary cortisol fell. The HADS anxiety subscale fell just short of significance (P < 0.06). The trial was run for the maker by contract research organizations.
Self-rated mood scores over 8 weeks
In a placebo-controlled trial in 110 adults with major depression who stayed on their antidepressants, 10 billion CFU a day for 8 weeks lowered Beck Depression Inventory scores from 17.4 to 9.1, against 18.2 to 15.6 with placebo (81 people completed). A later analysis of the same trial reported higher BDNF, a brain growth factor. The maker supplied the product.
Mood scores in two placebo-controlled trials
In two double-blind placebo-controlled trials, 3 billion CFU a day did not improve mood scores overall: one in 79 adults with low mood who took no psychiatric medicines (8 weeks; Lallemand funded the product and blood tests) and one in 116 adults with depression (60 days). In the larger trial, more people on the probiotic reached a minimum meaningful improvement (75% versus 54%).
Anxiety and wellbeing in healthy adults
In a 4-week placebo-controlled trial in 135 healthy adults, 3 billion CFU a day had no significant effect on wellbeing, quality of life, emotional regulation or anxiety across the whole group. In a secondary analysis, participants with healthier lifestyle habits who took the probiotic had better anxiety, emotional regulation and mindfulness scores.
Re-analysis of the same 30-day trial
A second paper by the same group re-analyzed the same 30-day trial and again reported lower distress scores, including among participants whose starting urinary cortisol was low. Because these are the same participants reported a second time, it cannot confirm the first result; it is one trial published twice.
Calmer behavior in rats (animal study only)
In rats, the 2011 trial paper also reported less anxiety-like behavior in a defensive burying test, which the authors describe as a screening model for anti-anxiety agents. This is an animal result, not a human one.
Mechanism of action
GABA signaling (animal work only)
Animal work suggests GABA-related signaling may be involved in the calmer behavior seen in rats. This has not been measured in people taking this combination.
HPA axis cortisol attenuation
In the single 30-day human trial, 24-hour urinary free cortisol fell, which suggests some effect on the body's stress-hormone system. That is one measurement, in one trial, in healthy volunteers.
Vagal afferent signaling
Communication from the gut to the brain along the vagus nerve is one proposed route for probiotic effects on mood. No study cited on this page tested this for these two strains, so treat it as a theory rather than a demonstrated effect.
Short-chain fatty acid production
Gut bacteria can produce short-chain fatty acids that act on the gut lining and on nerve signalling. This is general probiotic theory; short-chain fatty acids were not measured in the studies cited on this page.
Tryptophan / serotonin precursor modulation
Changes in how the gut handles tryptophan could in theory affect the supply of the building blocks of serotonin. In the 8-week depression trial, the kynurenine to tryptophan ratio did not differ between groups in the main comparison and was lower with the probiotic only after adjusting for the amino acid isoleucine.
Gut barrier integrity and reduced systemic inflammation
Probiotics are proposed to help keep the gut lining intact and limit inflammatory molecules passing into the blood. In the low-mood trial, inflammatory blood markers did not change compared with placebo.
Synergistic two-strain combination
The human trials tested the two strains together, so their results cannot be credited to either strain on its own. No study cited here compared the combination against the single strains, so a synergy claim is not supported.
BDNF, a brain growth factor
In a post hoc analysis of the 8-week depression trial, blood levels of BDNF rose with the probiotic compared with placebo and the prebiotic, and higher BDNF tracked with lower depression scores. This is an exploratory analysis of one trial.
Clinical trials
Randomized, double-blind, placebo-controlled parallel trial; 3 billion CFU a day for 30 days, published with a separate rat experiment (Messaoudi et al. 2011, Br J Nutr)
Healthy adult volunteers; the abstract does not give the number of participants
The overall distress index (HSCL-90 global severity), somatization, depression and anger-hostility scores, the HADS global score, a problem-solving coping score and 24-hour urinary free cortisol improved (P < 0.05). The HADS anxiety subscale fell just short (P < 0.06). Run by contract research organizations for the maker; the paper was published online in October 2010.
Randomized, double-blind, placebo-controlled trial; one sachet of 10 billion CFU a day, a galactooligosaccharide prebiotic or placebo for 8 weeks (Kazemi et al. 2019, Clin Nutr)
110 adults with major depressive disorder who were taking antidepressants; 81 completed
Beck Depression Inventory scores fell from 17.39 to 9.1 with the probiotic versus 18.18 to 15.55 with placebo and 19.72 to 14.14 with the prebiotic (p = 0.042). The kynurenine to tryptophan ratio did not differ between groups unless adjusted for isoleucine. Lallemand supplied the products.
Randomized, double-blind, placebo-controlled trial; one 3 billion CFU sachet a day for 8 weeks (Romijn et al. 2017, Aust N Z J Psychiatry)
79 adults with at least moderate low mood scores, not taking psychiatric medicines; 10 dropped out
No difference from placebo on any psychological measure (effect sizes 0.07 to 0.16) or blood marker. Responders were 9 of 39 on the probiotic and 10 of 38 on placebo. Lallemand provided the products and paid for blood testing, and the lead author has received research funding from Lallemand.
Randomized, placebo-controlled trial; 3 billion CFU of Cerebiome® for 4 weeks (Morales-Torres et al. 2023, Nutrients)
135 healthy adults
No significant effect on wellbeing, quality of life, emotional regulation, anxiety, mindfulness or body awareness in the whole sample. In a secondary model, the probiotic combined with high healthy-behavior scores predicted better anxiety, emotional regulation and mindfulness. Rosell-Lallemand supplied the products; the authors report no financial ties to it.
Randomized, placebo-controlled trial; 3 billion CFU a day in capsules for 12 weeks (Wiącek et al. 2025, Int J Mol Sci)
26 female dancers randomized; 16 analyzed (5 probiotic, 11 placebo)
No improvement in gastrointestinal symptoms on the Rome IV questionnaire. The stool metabolite profile shifted in the probiotic group. No adverse events. Four authors are shareholders, employees or paid by a probiotic company; the product was made by Sanprobi with Lallemand probiotic powder.
Randomized, double-blind, placebo-controlled parallel trial; one 3 billion CFU capsule a day for 60 days (Gawlik-Kotelnicka et al. 2024, Nutrients)
116 adults with a depressive disorder, some taking antidepressants; depression scores analyzed in 94
No overall difference from placebo in depression scores (p = 0.45). More people on the probiotic reached a minimum clinically important improvement (74.5% versus 53.5%, p = 0.03). People with more metabolic problems, such as excess belly fat, improved less. No serious adverse events. Funded by the Medical University of Lodz; the product was made by Sanprobi with Rosell-Lallemand probiotic powder.