Probiotics Enhance Efficacy of Antidepressants for Major Depressive Disorder – Neuroscience News

Summary: A probiotic blend made up of 14 strains of bacteria can improve the treatment of major depressive disorder when used alongside antidepressants.

This pilot study highlights the potential of probiotics to promote mood improvements over an eight-week period. It’s a groundbreaking exploration of how improved gut health with probiotics could pave the way for a new approach to boosting mood and mental health.

According to the researchers, these encouraging results lay a solid foundation for further exploration in larger studies.

Main aspects:

  1. This research found that a probiotic blend of 14 strains can potentially support improvements in depression and anxiety scores over an eight-week period when used alongside antidepressants.
  2. The study, one of the first in a Western population to demonstrate the good tolerability and positive effects of probiotics on mental health, offers a potential new pathway to support mood and mental health.
  3. A double-blind, randomized, placebo-controlled design was employed in this pilot study. The participants were adults diagnosed with major depressive disorder who showed an incomplete response to antidepressants.

Source: King’s College London

A new study published today (June 14) inJAMA Psychiatryfound evidence that supplementing your diet with a probiotic blend containing 14 strains of bacteria can help people who are being treated for major depressive disorder with antidepressants.

The research, conducted by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at Kings College London and in collaboration with ADM Protexin, part of ADM, has demonstrated the potential of probiotic supplementation to support improvements in depression and anxiety scores multiples over an eight-week period.

This shows a bottle of pills.
There were significant improvements reported as measured against the gold standard rating scales for depression and anxiety. Credit: Neuroscience News

The pilot study is one of the first studies in a Western population to show both good tolerability of probiotics and positive effects on mental health in adults with depression who are currently taking antidepressants.

According to the researchers leading the study, the findings provide a strong foundation to further investigate the benefits of this probiotic dietary supplement for supporting mood and mental health in a larger study.

There is growing evidence that the gut microbiota (the large and dynamic community of microorganisms that inhabit the gut) has a role to play in regulating mood.

The study was a double-blind, randomized, placebo-controlled study designed as an initial exploration of whether improving gut health through the use of probiotic supplements containing beneficial bacteria could act as a novel pathway to support mood and mental health.

In this pilot study, 49 adults diagnosed with major depressive disorder and with an incomplete response to a prescription for antidepressants were given a proprietary probiotic supplement with a widely available blend of 14 strains or an identical placebo (24 received the probiotic).

Over the course of eight weeks, both groups demonstrated improvement in symptoms, but greater improvements were seen in the probiotic group from week four onwards.

There were significant improvements reported as measured against the gold standard rating scales for depression and anxiety.

Professor James Stone, the study’s senior researcher who started at Kings IoPPN and is now at Brighton and Sussex Medical School, said: ‘Partial or partial response to antidepressants is a huge issue and this study is a first. important step in the exploration of therapeutic potential”. of probiotics as a treatment for depression.

“We found that probiotics were an acceptable and tolerable supplement in people already taking antidepressant medications.

“This now paves the way for studies examining whether we see these beneficial effects of probiotics on depression and anxiety in larger patient populations.

Dr Viktoriya Nikolova, first author of the Kings IoPPN study, said: “The gut-brain axis is a truly fascinating and rapidly evolving area of ​​microbiome research. The results of this pilot study represent a major step forward in our understanding of the role of probiotics in mood and mental health.

Dr. Richard Day, vice president of medical affairs at ADM, said:According to the World Health Organization, approximately 5% of adults suffer from depression, with a significant number not fully responding to standard treatment options.

“This study is one of the few clinical trials to evaluate the benefits of supplementing the diet with probiotics alongside standard-of-care antidepressant medications. These exciting findings add to our understanding of the link between the gut microbiome and mental health.

This study was made possible through a CASE MRC Industrial PhD fellowship with ADM Protexin as an industrial partner and charitable donations from Freya Green.

Financing: He has also received funding from the National Institute for Health and Care Research (NIHR) Biomedical Research Center in South London and the Maudsley NHS Foundation Trust and Kings College London.

About this novelty of research in psychopharmacology and depression

Author: Amelia Remmington
Source: King’s College London
Contact: Amelia Remmington – King’s College London
Image: The image is credited to Neuroscience News

Original research: Free access.
“Acceptability, tolerability, and estimates of purported treatment effects of probiotics as adjunctive treatment in patients with depression: A randomized clinical trial” by James Stone et al. JAMA Psychiatry


Acceptability, tolerability, and estimates of putative treatment effects of probiotics as adjunctive treatment in patients with depression: a randomized clinical trial


The microbiota-gut-brain axis is a promising target for new treatments for mood disorders, such as probiotics. However, few clinical trials have been conducted and more data on safety and efficacy are needed to support this treatment approach.


To provide acceptability and tolerability data and intervention effect size estimates for probiotics as adjunctive treatment for patients with major depressive disorder (MDD).

Design, setting and participants

In this single-center, double-blind, placebo-controlled, randomized pilot clinical trial, adults aged 18 to 55 years with MDD who were taking antidepressant medications but with an incomplete response were studied. A random sample was recruited from primary and secondary care services and general advertising in London, UK. Data was collected between September 2019 and May 2022 and analyzed between July and September 2022.


Multi-strain probiotic (8 billion colony forming units per day) or placebo every day for 8 weeks in addition to current antidepressant medication.

Main results and measures

The pilot outcomes of the study were retention, acceptability, tolerability, and estimates of the presumed treatment effect on clinical symptoms (depression: Hamilton Depression Rating Scale [HAMD-17] and Inventory of depressive symptoms [IDS] scores; Anxiety: Hamilton Anxiety Rating Scale [HAMA] and General Anxiety Disorder [GAD-7] scores) to be used as indicators for a definitive test.


Of the 50 participants included, 49 received the intervention and were included in the intent-to-treat analyses; of these, 39 (80%) were female, and the mean (SD) age was 31.7 (9.8) years. A total of 24 were randomized to the probiotic and 25 to the placebo.

Attrition was 8% (1 in the probiotic group and 3 in the placebo group), adherence was 97.2%, and no serious adverse reactions occurred. For the probiotic group, mean (SD) HAMD-17 scores at weeks 4 and 8 were 11.00 (5.13) and 8.83 (4.28), respectively; IDS, 30.17 (11.98) and 25.04 (11.68); HAMA, 11.71 (5.86) and 8.17 (4.68); and GAD-7, 7.78 (4.12) and 7.63 (4.77). For the placebo group, the mean (SD) HAMD-17 scores at weeks 4 and 8 were 14.04 (3.70) and 11.09 (3.22), respectively; IDS, 33.82 (9.26) and 29.64 (9.31); HAMA, 14.70 (5.47) and 10.95 (4.48); and GAD-7, 10.91 (5.32) and 9.48 (5.18).

Standardized effect sizes (SES) from linear mixed models demonstrated that the probiotic group achieved greater improvements in depressive symptoms according to HAMD-17 scores (week 4: SES, 0.70; 95% CI, 0.01-0 .98) and IDS Self Report scores (week 8: SES, 0.64; 95% CI, 0.03-0.87) as well as major improvements in anxiety symptoms by HAMA scores (week 4: SES, 0. 67; 95% CI, 0-0.95; week 8: SES, 0.79; 95% CI, 0.06-1.05), but not GAD-7 scores (week 4: SES, 0.57; 95% CI, 0.01 to 0.82; week 8: SES, 0.32; 95% CI, 0.19 to 0.65), compared with the placebo group.

Conclusions and Relevance

The acceptability, tolerability, and estimated effect sizes on key clinical outcomes are promising and encourage further investigation of probiotics as an adjunctive treatment for people with MDD in a definitive efficacy study.

Trial registration ID: NCT03893162

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