Gut Feeling: Understanding the Mechanisms Underlying the Antidepressant Properties of Probiotics

Inclusion criteria

for MDD participants:

• aged 18-55;
• currently in a depressive episode according to DSM-5 criteria, who are currently on antidepressant treatment but remain symptomatic (HAM-D17 score >13);
• on stable treatment regimen of an approved treatment for at least 6 weeks;
• non-smokers;
• for participants willing to take part in the neuroimaging component: right-handed, no contraindications, non-claustrophobic, weight <126kg;

Exclusion criteria

for MDD participants:

• eating disorder, bipolar disorder, schizophrenia or psychotic symptoms;
• substance dependence in the past year, except for caffeine;
• active suicidal ideation;
• use of probiotic supplements in the past 2 weeks, or regular use of a probiotic;
• use of antibiotics in the past 12 weeks;
• history of allergic reaction to any of the components of BioKult;
• history of history of a systemic medical illness;
• current presence of significant GI problems or disease or history of major GI surgery;
• pregnancy or breastfeeding;
• following a dietary regimen unrepresentative of the general population (e.g. fasting or following a specific diet);
• regular/current use of antacids, proton pump inhibitors, laxatives, antidiarrheals;

Inclusion criteria

for Healthy Volunteers:

• Aged 18-55;
• No current or historic presence of depression, other psychiatric disorder or substance dependence
• No history of a systemic medical illness;
• No family history of psychiatric disorder;
• Non-smoker;
• Not used probiotic supplements in the past 2 weeks, nor regular use of a probiotic;
• Not used antibiotics in the past 12 weeks;
• No current presence of gastrointestinal disease, or history of major GI surgery;
• No reported regular/current use of antacids, proton pump inhibitors, laxatives, antidiarrheals;
• pregnancy or breastfeeding;
• not currently following a dietary regimen or dietary restrictions unrepresentative of the general population (e.g. fasting or following a specific diet);