4. Discussion
sleep disturbance, anxiety, pain, depression, stress reduction
This exploratory trial evaluated the effect of Our main findings are in line with a recent meta-analysis assessing the effects of probiotics on stress in healthy subjects, showing that probiotics can reduce the subjective stress level in healthy volunteers without having a significant effect on the cortisol concentration [The baseline data obtained from subjective reports clearly showed a healthy population without suspicion of sleep disturbance. Although this initial status left limited space for improvement, we observed improved subjective sleep quality. This finding is in line with a recent study that showed an overall improvement in sleep quality and the duration of sleep using another The MAST procedure induced the anticipated increase in salivary cortisol [The finding that participants in the placebo group increased their positive mood scores on the PANAS after the MAST stressor was unexpected but may be due to the participants in this group feeling relieved that the study procedures were over with, since these participants reported a higher pain experience.In contrast to the One possible explanation for the lack of significant results on any other stressor-dependent subjective measures is that the sample size may not have been large enough to detect any differences.To investigate whether the probiotic intervention led to an overall change across all assessed parameters, we conducted a multivariate analysis that revealed a positive correlation between stress reduction and reductions in anxiety and depression. This positive association is in line with findings that perceived stress may increase negative emotions such as anxiety and depression [There are several mechanisms that could link the probiotic effect to the gut microbiome and host, leading to the reduction in perceived stress and the correlating benefits for anxiety and depression. For example, Overall, our results support the potential of specific probiotics being used to reduce perceived stress and will guide future clinical trial design to confirm the observed changes. Nevertheless, it is important to note that this exploratory clinical trial has several limitations. A larger, powered trial is warranted to confirm the findings of this exploratory trial, though the current findings can guide the design of any future confirmatory clinical studies in terms of effect size and expected variability. Moreover, the dosage and duration of probiotic supplementation play a key role in their effectiveness for reducing stress and improving mood. Some studies showed that higher doses of probiotics [Our results show, for the first time, that long-term oral supplementation with 