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A new study has tested if a daily, 4-week intake of a multispecies probiotic improved emotional processing in people with untreated moderate depression.

Bacteria Bifidobacterium, part of normal flora of human intestine, used as probiotics and in yoghurt production.

Dietary supplementation with probiotics - live cultures of "good" bacteria - has been shown to influence brain function, but the understanding of the underlaying mechanisms involved in this remain elusive.

Associate Professor Phil Burnet, Department of Psychiatry, University of Oxford, said:


'Our study shows that taking a probiotic supplement alters emotional processing and improves mood in people with moderate depression. These data provide further evidence for gut bacteria affecting human brain function.

'Understanding the influence of probiotics on emotions may suggest how they should be most effectively combined with other interventions in the treatment of mental health conditions. People with moderate depression are often reluctant to seek medical help as they may be worried about taking medication. Our findings suggest that probiotics could be used as an early intervention to help reduce the risk of people with mild to moderate depression developing a major depressive disorder, which is more debilitating and often difficult to treat. However, it is important to note that probiotics will never, and should not, replace current pharmacological and psychological therapies.'

The study included 71 participants in a randomised double-blind, placebo-controlled trial. Results showed that the participants who took the probiotic had increased accuracy at identifying faces expressing all emotions and vigilance to neutral faces, this is different to the reported action of commonly used antidepressants, which reduce attention to negative emotions.

Associate Professor Burnet continues:

'Testing a larger population of people with other probiotics and narrowing down exactly which bacteria are influencing the processes in the periphery that lead to changes in the brain would be a helpful next step. This would then have the potential to lead to the development of new treatments for depression when conventional approaches may not be appropriate.'

Read the full paper, Multispecies probiotic administration reduces emotional salience and improves mood in subjects with moderate depression: a randomised, double-blind, placebo-controlled study.