Gut feeling: can a probiotic lift depression?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Outpatient or inpatient participants, aged 18 to 65 years (inclusive), of any sex * Current episode meets Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for depressive disorder * Baseline score on the 17-Item Hamilton Depression Rating Scale is 7 to 24, inclusive * No concomitant use of antidepressants or other psychotropic medications during the study * Elementary school education or above, able to understand the study requirements and complete the rating scales * Participant personally signs the informed consent form and is willing to complete follow-up according to the study protocol Exclusion Criteria: * Current or past diagnosis, according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria, of bipolar disorder, schizophrenia spectrum and other psychotic disorders, neurocognitive disorders, neurodevelopmental disorders, or substance-related and addictive disorders * Presence of significant psychotic symptoms, such as delusions or hallucinations * Severe or unstable diseases of the central nervous system, cardiovascular system, respiratory system, liver, kidneys, endocrine system, hematologic system, or other systems that, in the investigator's judgment, make the participant unsuitable for the study * Evident suicide risk, defined as a score of 1 or higher on the suicide item of the 17-Item Hamilton Depression Rating Scale * Active inflammatory disease * Gastrointestinal infection, tumor, or other organic digestive disease, including but not limited to irritable bowel syndrome, Crohn disease, ulcerative colitis, or celiac disease * History of major gastrointestinal surgery * Use of antibiotics, probiotics, prebiotics, or related functional products within 1 month before study entry * Allergy to the study product or any of its components * Pregnant or breastfeeding women * Unable or unwilling to take the study product as required by the protocol * Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study