The Effects of Probiotics on Depression: Can a Daily Drink of Good Bacteria Improve Mental Wellbeing?

INTERVENTION: 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. CONDITION: Depression PRIMARY OUTCOME: mean score on the Beck Depression Inventory – II mean score on the Depression Anxiety Stress Scale‐21 Proportion of participants with subclinical or clinical diagnosis of Major Depressive Disorder (MDD), on the Mini International Neuropsychiatric Interview (M.I.N.I) SECONDARY OUTCOME: mean score on Beck Anxiety Inventory mean score on Cognitive Reactivity Scale 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