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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The Effects of Probiotics on Depression: Can a Daily Drink of Good Bacteria Improve Mental Wellbeing?
Scientific title
A placebo-controlled RCT of the use of probiotics to reduce depressive symptoms in adults with depression
Secondary ID [1] 287471 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Depression 296204 0
Condition category
Condition code
Mental Health 296482 296482 0 0

Study type
Description of intervention(s) / exposure
The intervention in this trial will be a probiotic supplied by Winclove Probiotics. Participants will be asked to consume 2 x 2g of the probiotic daily over the course of 8 weeks by dissolving the freeze-dried powder in water and drinking it, and provide weekly measures of mood and depression during this period. Pre and post-measures of depressive symptoms will be taken prior to and after the conclusion of the 8 week probiotic period.
The probiotic powder contains the following ingredients: maize starch, maltodextrins, +/- probiotic bacteria (B. bifidum W23, B. lactis W52; L. acidophilus L37; L. brevis W63, L. casei W56; L. salivarius W24; Lc. lactis W19 and W58), minerals, vegetable protein. The number of Colony Forming Units (CFU) is 2.5 x 10^9 CFU/gram. Participant adherence to probiotic consumption will be monitored through asking them to record how many sachets they took each day, as well as returning of both empty and full probiotic sachets to the research team each week.
Intervention code [1] 292854 0
Treatment: Other
Comparator / control treatment
The control group will be a placebo control. Participants in this group will be given a freeze-dried powder containing the same ingredients minus the active probiotics as the intervention group, and the placebo and probiotic will be identical in terms of taste, appearance and smell. Participants will consume 2 x 2g of the placebo daily over an 8 week period. The control group will complete the same pre and post-measures of depressive symptoms, as well as weekly measures of mood and depression during the 8 week probiotic/placebo period.
Control group

Primary outcome [1] 296109 0
Proportion of participants with subclinical or clinical diagnosis of Major Depressive Disorder (MDD), on the Mini International Neuropsychiatric Interview (M.I.N.I)
Timepoint [1] 296109 0
baseline, post-intervention (8 weeks)
Primary outcome [2] 296110 0
mean score on the Beck Depression Inventory – II
Timepoint [2] 296110 0
baseline, post-intervention (8 weeks)
Primary outcome [3] 296111 0
mean score on the Depression Anxiety Stress Scale-21
Timepoint [3] 296111 0
weekly, beginning at baseline through to the end of the intervention period (8 weeks)
Secondary outcome [1] 317532 0
mean score on Beck Anxiety Inventory
Timepoint [1] 317532 0
baseline, post-intervention (8 weeks)
Secondary outcome [2] 317533 0
mean score on Cognitive Reactivity Scale
Timepoint [2] 317533 0
baseline, post-intervention (8 weeks)

Key inclusion criteria
Participants must be aged 18 years or above, and at screening have a subclinical or clinical diagnosis of Major Depressive Disorder confirmed using the Mini International Neuropsychiatric Interview (M.I.N.I). Participants must be able to travel to UTS (Ultimo) to participate in the study, and must have access to and regularly check a valid email address. Participants must also be willing to complete questionnaires measuring mood, general wellbeing and health, as well as a measure of blood pressure and a stool sample
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Key exclusion criteria: Participants will be excluded from the trial if they meet any of the following restrictions: currently taking antibiotics or probiotic supplements, taken antibiotics within the 2 weeks prior to the start of the trial, diagnosed with HIV/AIDS, cancer, Crohn’s disease or ulcerative colitis, currently undergoing chemotherapy, lactose-intolerant, gluten-intolerant, high-risk alcohol consumption, experiencing severe depressive symptoms, actively suicidal or experiencing severe suicidal ideation, actively self-harming, pregnant or planning to be pregnant within the time-course of this study, diagnosed with Bipolar disorder, a Personality disorder, a psychotic disorder or otherwise experiencing psychosis, receiving any other treatment for mental health issues (including medications such as anti-depressants) or currently participating in another clinical trial.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Participants will be randomly allocated to the control or intervention groups, through use of a computerised randomiser. Probiotics/placebos will be allocated and labelled prior to the commencement of the trial, and research team members will not know participant allocation during the trial and data analysis period. After data has been analysed, and any direction of effect noted, treatment allocation will be unblinded.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The method of sequence generation will be through using a computerised randomiser.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Sample size was calculated by a review of the literature on studies for depression treatment, with a focus on the expected effect size. Klein, Jacobs and Reinecke (2007) indicate that an effect size of 0.53 (medium effect size) is the average for CBT trials on depression, which was reflected in the literature we reviewed. A power analysis via the program G*Power (computerised statistical program, Universitat Dusseldorf) indicated that 36 participants per group would be required to detect a medium effect size with 80% power. This is a total of 72 participants.
Further statistical analyses will involve an ANCOVA holding pre-existing baseline measures of depressive symptoms and anxiety as co-variates. Based on previous literature, a sample size of 36 participants per group is large enough to encompass a range of depression severities.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 292049 0
Name [1] 292049 0
University of Technology Sydney
Address [1] 292049 0
UTS, 15 Broadway, Ultimo, NSW, 2007
Country [1] 292049 0
Primary sponsor type
University of Technology Sydney
Graduate School of Health, Building 7, UTS, 15 Broadway, Ultimo, NSW, 2007
Secondary sponsor category [1] 290717 0
Name [1] 290717 0
Address [1] 290717 0
Country [1] 290717 0
Other collaborator category [1] 278625 0
Name [1] 278625 0
Dr Saskia van Hemert
Address [1] 278625 0
Winclove Probiotics
Winclove B.V. Hulstweg 11 1032 LB Amsterdam The Netherlands
Country [1] 278625 0

Ethics approval
Ethics application status
Ethics committee name [1] 293530 0
UTS Human Research Ethics Committee
Ethics committee address [1] 293530 0
UTS, 15 Broadway, Ultimo, NSW, 2007
Ethics committee country [1] 293530 0
Date submitted for ethics approval [1] 293530 0
Approval date [1] 293530 0
Ethics approval number [1] 293530 0
UTS HREC REF NO. 2015000438

Brief summary
Whilst CBT has been validated as an effective psychological treatment for depression, efficacy rates of treatment still indicate the need for improvement. Emerging evidence indicates that the relationship between the gut and the brain can be harnessed, so that changes in gastrointestinal health can have positive or negative effects on mental health, and vice versa. This trial investigates whether administration of a probiotic is effective in reducing levels of depression in a population of depressed adults. Participants will consume the probiotic daily, and provide measures of mood throughout the study period. We will measure baseline and post-intervention levels of depressive symptoms, and compare changes in levels of depression between a group provided with the probiotic, and a control group given a placebo.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 60330 0
Dr Lynette Roberts
Address 60330 0
Level 4, GSH, Building 7 UTS, 15 Broadway, Ultimo, NSW, 2007

Country 60330 0
Phone 60330 0
+61 2 9514 7202
Fax 60330 0
Email 60330 0
Contact person for public queries
Name 60331 0
Dr Lynette Roberts
Address 60331 0
Level 4, GSH, Building 7 UTS, 15 Broadway, Ultimo, NSW, 2007
Country 60331 0
Phone 60331 0
+61 2 9514 7202
Fax 60331 0
Email 60331 0
Contact person for scientific queries
Name 60332 0
Dr Lynette Roberts
Address 60332 0
Level 4, GSH, Building 7 UTS, 15 Broadway, Ultimo, NSW, 2007
Country 60332 0
Phone 60332 0
+61 2 9514 7202
Fax 60332 0
Email 60332 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary