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Probiotics as Adjunctive Treatment in Major Depressive Disorder: Estimates of Treatment Effect and Underlying Mechanisms From a Double-Blind Placebo-Controlled Randomised Pilot Trial

Published online by Cambridge University Press:  07 July 2023

Viktoriya Nikolova ,
Anthony Cleare ,
Allan Young  and
James Stone
Viktoriya Nikolova*
Affiliation:
ADM Protexin, London, United Kingdom Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
Anthony Cleare
Affiliation:
Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom National Institute for Health and Care Biomedical Research Centre, South London and Maudsley NHS Foundation Trust and King's College London, London, United Kingdom South London and Maudsley NHS Foundation Trust, Bethlem Royal Hospital, London, United Kingdom
Allan Young
Affiliation:
Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom National Institute for Health and Care Biomedical Research Centre, South London and Maudsley NHS Foundation Trust and King's College London, London, United Kingdom South London and Maudsley NHS Foundation Trust, Bethlem Royal Hospital, London, United Kingdom
James Stone
Affiliation:
Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom Brighton and Sussex Medical School, Brighton, United Kingdom
*
*Corresponding author.
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Abstract

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Aims

Despite considerable preclinical evidence, clinical trials assessing the effects of probiotics on individuals with major depressive disorder (MDD) are scarce. This study aimed to provide further evidence of the acceptability, tolerability and putative efficacy of probiotics in this patient group and to improve our understanding of the underlying mechanisms of action.

Methods

This double-blind randomised placebo-controlled pilot and mechanistic trial investigated the effects of an 8-week adjunctive multi-strain probiotic intervention in adults with MDD taking antidepressants. Psychiatric data and stool and blood samples were collected at baseline, week 4 and week 8. A computer-based emotion recognition task was also administered. Stool samples from 25 matched healthy controls were also obtained.

Results

49 participants, randomised to probiotic (n = 24) or placebo (n = 25), were included in intent-to-treat analyses. Standardised effect sizes (SES) from linear mixed models demonstrated that the probiotic group attained greater improvements in depressive (HAMD week 4: SES [95%CI] = 0.70[0.01, 0.98]; IDS week 8: SES [95%CI] = 0.64 [0.03, 0.87]) and anxiety symptoms (HAMA week 4: SES [95%CI] = 0.67 [0.00, 0.95]; week 8: SES [95%CI] = 0.79 [0.06, 1.05]), compared to the placebo group. Attrition was 8% (n = 3 placebo, n = 1 probiotic), adherence was 97.2% and there were no serious adverse reactions. The probiotic modified the composition of the faecal microbiota by normalising richness and diversity towards healthy control levels. The probiotic also increased levels of specific taxa, including Bacillaceae (FDR p < 0.05), which correlated with reductions in anxiety scores (FDR p < 0.05). There was no impact of treatment on levels of inflammatory cytokines (CRP, TNFα, IL-1β, IL-6, IL-17) or BDNF. However, probiotics showed a tendency to increase positive affective bias and improved the accuracy of recognition of all emotions, except sadness.

Conclusion

Compared to placebo, the probiotic group had greater improvement in depressive and anxiety scores, from as early as 4 weeks. The acceptability, tolerability and estimated effect sizes on key clinical outcomes are promising and encourage further investigation of this probiotic as add-on treatment in MDD. The beneficial effects of probiotics in this patient group may be partially mediated by modification of the composition of the gut microbiota and improvement of affective biases, inherent to depressive disorders.

Type
Research
Information
BJPsych Open , Volume 9 , Supplement S1: Abstracts from the RCPsych International Congress 2023, 10–13 July , July 2023 , pp. S64 - S65
Creative Commons
Creative Common License - CCCreative Common License - BYCreative Common License - NC
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by-nc/4.0), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. This does not need to be placed under each abstract, just each page is fine.
Copyright
Copyright © The Author(s), 2023. Published by Cambridge University Press on behalf of the Royal College of Psychiatrists

Footnotes

Abstracts were reviewed by the RCPsych Academic Faculty rather than by the standard BJPsych Open peer review process and should not be quoted as peer-reviewed by BJPsych Open in any subsequent publication.

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