The trial will be a four-arm, parallel group, prospective, randomized, double-blind, controlled design that will include 200 participants and will last 20 weeks. The probiotic preparation will contain Lactobacillus helveticus Rosell®-52, Bifidobacterium longum Rosell®-175. We will assess the level of depression, anxiety and stress, quality of life, blood pressure, body mass index and waist circumference, white blood cells count, serum levels of C-reactive protein, HDL cholesterol, triglicerides, fasting glucose, faecal microbiota composition and the level of some faecal microbiota metabolites, as well as inflammation markers and oxidative stress parameters in serum.

The trial may establish a safe and easy-to-use treatment option as an adjunct in a subpopulation of depressive patients only partially responsive to pharmacologic treatment.

Inclusion Criteria:

Depressive disorders diagnosed according to ICD Age between 18 and 70 years MADRS score >=13 Antidepressant and antianxiety medications or psychotherapy not changed 3 weeks prior to the beginning of the study DMS study groups: MetS diagnosed according to International Diabetes Federation (IDF)

Exclusion Criteria:

Pregnancy; An infection and/or treatment with antibiotics in the previous 4 weeks; Supplementation with pro- or prebiotics in the previous 4 weeks; Having a diagnosis of autoimmune, serious immunocompromised, inflammatory bowel diseases, cancer, IgE-dependent allergy, severe kidney failure or unstable thyroid dysfunction in the previous 4 weeks; Psychiatric comorbidities (except for specific personality disorder, additional specific anxiety disorder and caffeine or nicotine addiction); Regular treatment (more than 3 days a week) with proton-pump inhibitors (PPIs), metformin, laxatives, systemic steroids or nonsteroidal anti-inflammatory drugs (NSAIDs) in the previous 4 weeks; Following a specific diet or a significant change in dietary pattern in the previous 4 weeks; Significant change in daily physical activity or an extreme sport activity in the previous 4 weeks; Significant change in dietary supplementation in the previous 4 weeks; Significant change in smoking pattern in the previous 4 weeks; A major neurological disorder or any medical disability that may interfere with a subject's ability to complete study procedures; High risk of suicide according to Tool of Assessment of Suicide Risk (TASR); Is participating in, or has recently participated in, another research study involving an intervention which may alter outcomes of interest to this study; Any other condition or situation which, in the view of investigators, would affect the compliance or safety of the individual taking part; D study groups: MetS diagnosed according to International Diabetes Federation (IDF).