Effects of Probiotic Supplementation on Stress and Anxiety in Students

Inclusion Criteria: * Male or female students aged 18-40 years * At least moderate stress (DASS-21 Stress score ≥10) * Mild anxiety (DASS-21 Anxiety score 6-13) * No clinical depression (DASS-21 Depression score ≤9) * Willingness to maintain usual diet, physical activity, and intake of caffeinated beverages during the study * Written informed consent Exclusion Criteria: * Irritable bowel syndrome (Rome IV criteria) or any chronic intestinal disease (including celiac disease) * Known food allergies, immunodeficiency disorders, or immunosuppressive treatment * Antibiotic use within 4 weeks prior to screening * Any psychiatric illness within the past 5 years * Any malignant disease or autoimmune or allergic diseases (e.g., atopic dermatitis, asthma) * Use of systemic psychotropic medications or steroids; use of topical corticosteroid creams within 4 weeks prior to screening * Pregnancy, breastfeeding, or plans to become pregnant during the study * Probiotic or prebiotic consumption or planned dietary changes within 4 weeks prior to screening * Heavy caffeine consumption (\>4 cups of 300 mL coffee per day) * Drug or alcohol addiction or regular use of recreational drugs * Smoking more than 10 cigarettes per day