Researchers at the Leiden Institute of Brain and Cognition found that probiotics stopped people ruminating so much.
Rumination is when people focus on bad experiences and feelings from the past. Dr Laura Steenbergen, the study’s first author, said:
“Rumination is one of the most predictive vulnerability markers of depression. Persistent ruminative thoughts often precede and predict episodes of depression.”
In the study 40 people were given a sachet to take with water or milk every day for four weeks. Half of the people received sachets that contained a multispecies probiotic. The other half received a placebo for the four weeks. Before and afterwards people’s so-called ‘cognitive reactivity’ was measured.
‘Cognitive reactivity’ is the extent to which a sad mood can turn into something more serious.
The authors explained the results:
“…in the probiotics supplementation condition participants perceived themselves to be less distracted by aggressive and ruminative thoughts when in a sad mood.”
In other words, when people felt sad, those taking the probiotics ruminated less. The authors write:
“…studies have shown that the tendency to engage in ruminative thoughts is sufficient to turn mood fluctuations into depressive episodes, and that individuals who typically respond to low mood by ruminating about possible causes and consequences of their state have more difficulties in recovering from depression.”
Probiotics have been increasingly linked to good mental health. But this is the first study to identify this specific link. Dr Lorenza Colzato, another of the study’s authors, said:
“Even if preliminary, these results provide the first evidence that the intake of probiotics may help reduce negative thoughts associated with sad mood.
As such, our findings shed an interesting new light on the potential of probiotics to serve as adjuvant or preventive therapy for depression.”
The research is published in the journal Brain, Behavior, and Immunity (Steenbergen et al., 2015).