Beneficial bacteria help to reduce negative emotions

During the study, the researchers used a combination of methods to examine how emotions are regulated and how moods can be influenced. As part of the research, participants completed various psychological questionnaires about how they felt on a daily basis. In addition, they took part in computer-based tests, allowing the researchers to observe how they processed emotions. The study was conducted with healthy young adult participants who took a daily probiotic for one month, containing a mix of different bacteria.

The study shows that probiotics are more effective in reducing negative feelings than a placebo. The use of probiotics led to a decrease in feelings of anxiety, low mood, stress, and fatigue. Researcher Steenbergen noted: ‘It is striking that a positive effect of probiotics could be identified through the daily questions about how participants were feeling. However, it also became apparent that standard psychological questionnaires, which are commonly used in this type of research, were not sensitive enough to detect this change.’

What stood out is that it takes approximately two weeks for probiotics to begin reducing negative feelings – about the same amount of time as antidepressants. However, while antidepressants can suppress both positive and negative moods, probiotics appear to reduce only negative moods. This could be a significant advantage: probiotics do not affect positive feelings. Nevertheless, the researchers emphasise that probiotics are not a substitute for antidepressants. Moreover, the long-term effects remain unclear. In the future, probiotics might be used as an early intervention for depression, but further research is needed, according to researcher Steenbergen.