Probiotics Improve Emotional State in Healthy Adults, Studies Find

Probiotics Improve Emotional State in Healthy Adults, Studies Find

Daily mood reports reveal what traditional questionnaires miss - probiotics may increase negative emotions in healthy people and open new avenues for preventive mental health strategies.

In a study recently published in the journalNPJ mental health researchResearchers suggest that probiotics may reduce daily negative mood over time in healthy individuals, although this effect has not been captured by standard psychological questionnaires.

Finding ways to improve mental health and prevent the onset of mental health symptoms has become increasingly difficult. Despite advances in neuroscience, psychology, and psychiatry, there is an urgent need for novel, effective interventions, including behavioral therapies, neural stimulation, nutritional supplements, and pharmacotherapies. Research has shown that the gut microbial community can influence brain development, behavior and neurochemistry.

Studies have shown that rodents receiving gut microbiota from people with depression exhibit changes reminiscent of depression at behavioral and physiological levels. Various human studies have reported that probiotics can improve symptoms of anxiety, stress, and depression. Although some meta-analyses report beneficial effects, results remain inconsistent, particularly in nonclinical populations.

About the study

In the present study, researchers evaluated the effects of probiotics on emotion regulation. Individuals were eligible if they had a body mass index (BMI) of 18–30 kg/m , had not taken probiotics or antibiotics in the past three months, or were not taking any medications other than hormonal female contraceptives; Those who used drugs more than once a month or consumed >20 units of alcohol per week were excluded.

In addition, subjects were excluded if they had gastrointestinal, hepatic or renal disease, central nervous system (CNS) disorder or trauma, psychiatric or psychological disorder, allergy or hypersensitivity to nutrients (e.g. soy, gluten), or participated in nutritional programs in the past three months. Participants were randomized to take probiotics or a placebo for four weeks.

Probiotics were supplied as freeze-dried powder containing nine bacterial strains: Lactococcus lactis W19 and W58, Ligilactobacillus salivarius W24, Lacticaseibacillus casei W56, Levilactobacillus brevis W63, Lactobacillus acidophilus W37, Bifidobacterium lactis W51 and W52, and B. Bifidum W23. Placebo included a freeze-dried powder of maltodextrins and cornstarch. In addition, participants completed several common pre- and post-intervention emotion questionnaires.

These included the Center for Epidemiological Studies Depression Scale (CES-D), Positive and Negative Affect Schedule (PANAS), Buss-Perry Aggression Questionnaire (BPAQ), Emotion Reactivity Scale, Bermond–Vorst Alexithymia Questionnaire (BVAQ), Penn State Worry Questionnaire (PSWQ), Multidimensional Assessment of Interoceptive Awareness (MAIA), Perceived Stress Scale (PSS) and Suffering Index for Depression Sensitivity-Revised (Leids-R).

The FERT recognition recognition task (FERT) analyzed emotion identification accuracy, and the dot-probe task assessed selective attention to emotional facial expressions. Participants also reported their stool characteristics and mood each day. Group differences were assessed using the Wilcoxon signed-rank test or two-sample t tests. An exploratory analysis determined whether pre-intervention questionnaire results could predict which individuals would respond best to probiotics.

Results

In the study, 44 healthy adults were assigned to each group. Both groups had similar characteristics: The subjects were 22.3 years old and had a BMI of 23 kg/m². The questionnaires provided little evidence that emotion regulation changed significantly as a result of the intervention. PSWQ scores decreased after the intervention for both groups; However, only placebo recipients showed significant concern.

The probiotic group (darker color) is shown below the placebo group (lighter color), and error bars show the 95% confidence interval of the mean change.

The probiotics group scored higher on Maia's non-distracting subscale than the placebo group. This meant that the probiotic group had a greater tendency to be distracted by discomfort or pain after the intervention.

Furthermore, there was no treatment effect on bowel frequency/discomfort or the Bristol Stool Scale. There was no difference between groups for the dot-probe task.

For Fert, emotion intensity predicted recognition accuracy, which also varied by type of emotional expression. Nevertheless, there was a main effect of the session; Subjects were more accurate in the post-intervention session. A marginally significant interaction between session and group was observed, such that the probiotic group had marginally improved detection accuracy post-intervention.

Additionally, the probiotic group showed reduced negative mood, particularly after two weeks, as measured by daily mood self-reports, capturing changes not detected by traditional questionnaires. Exploratory analysis revealed some correlation between pre-intervention ratings and change in daily negative feelings in probiotic recipients. Importantly, only the Suffer-R risk aversion subscale predicted significant improvement in negative mood.

Conclusions

Taken together, there was no evidence that probiotics were beneficial for questionnaire measures of emotion; However, they were associated with reductions in negative mood over time when assessed through daily mood tracking. Despite the use of multiple questionnaires, the only differences after the intervention were the lower scores of the probiotics group on a MAIA subscale and the placebo group on the PSWQ.

The study authors emphasize that pre- and post-intervention questionnaires may not be sufficiently sensitive to detect subtle emotional changes in healthy individuals, while daily mood tracking provides a more nuanced and temporally rich assessment. In particular, risk-averse individuals may show greater reductions in negative moods with probiotics.

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