A Pilot Study of Synbiotics in Adults With Depressive Symptoms

Inclusion Criteria: * Individuals aged 18 or above * Patient Health Questionnaire-9 (PHQ-9) score between 5 to 14 * Literate and can complete the self-report questionnaires * Able to understand the consent and sign the informed consent form Exclusion Criteria: * Current diagnosis of substance abuse or dependence; * A current or past history of bipolar disorder, manic or hypomanic episodes, schizophrenia, personality disorder, posttraumatic stress disorder (PTSD), intellectual disability, neurodegenerative disorders (e. g, Parkinson's disease) or organic mental disorder * Requiring immediate psychiatric care (e. g, imminently suicidal subjects) or have attempted suicide in the past 3 months * Use of antipsychotics, antidepressants or sedatives, unless on a stable dose in the last 4 weeks * History of severe organ failure, renal failure on dialysis, HIV infection * Active malignancy within 5 years * History of major surgery on the gastrointestinal tract, except cholecystectomy and appendectomy in the past 5 years * Night shift work * History of antibiotic use within 4 weeks * History of allergy to probiotics or lactose leading to a severe allergic reaction * Known pregnancy or lactating