Effects of Probiotic Supplementation on Stress and Anxiety in Students

The gut-brain axis enables bidirectional communication between the gastrointestinal tract and the central nervous system. Emerging evidence suggests that selected probiotic strains (psychobiotics) may modulate stress responses and emotional regulation. University examination periods constitute a predictable model of transient psychological stress in otherwise healthy individuals.

This study investigates whether daily supplementation with a probiotic combination of Lactobacillus plantarum LP140 and Bifidobacterium breve BB010 reduces perceived stress and improves related psychological parameters in healthy students exposed to exam-related stress. Two hundred male and female students aged 18-40 years with at least moderate stress and mild anxiety, but without clinical depression, will be enrolled at the Medical University of Lublin, Poland. After providing written informed consent and confirming eligibility criteria, participants will be randomized in a 1:1 ratio to receive either a probiotic formulation containing Lactobacillus plantarum LP140 and Bifidobacterium breve BB010 (total daily dose of 1 × 10¹⁰ colony-forming units) or a matching placebo.

The investigational product and placebo will be identical in appearance and administered orally once daily (two capsules) for 8 weeks. Randomization will be computer-generated, and both participants and investigators will remain blinded to treatment allocation throughout the study. The intervention will begin approximately six weeks before the first scheduled academic examination. Study assessments will be conducted at baseline, at week 5 (approximately one week before the first examination), and at week 8 (±3 days before a subsequent examination). Psychological and functional parameters will be collected using validated self-report instruments administered electronically, with selected assessments performed during on-site visits. Participants will be asked to maintain their usual diet, physical activity, and caffeine intake during the study period. Safety and tolerability will be monitored throughout the intervention, and adverse events will be recorded using an electronic reporting system with daily reminders.

The study is powered to detect clinically meaningful differences between groups in perceived stress levels and will be analyzed using appropriate covariance-based statistical models adjusted for baseline values and relevant covariates. All participant data will be coded to ensure confidentiality and handled in accordance with applicable data protection regulations.

• Change in stress, anxiety and depression scores [Срок оценки: Change in DASS-21 Stress, Anxiety, and Depression subscale scores from baseline to week 5 and week 8 (±3 days) compared to placebo.]
• Change in sleep quality score [Срок оценки: Change in Pittsburgh Sleep Quality Index (PSQI) global score from baseline to week 5 and week 8 (±3 days) compared to placebo.]
• Change in sense of coherence score [Срок оценки: Change in Sense of Coherence Scale - 29 Items (SOC-29) total score from baseline to week 5 and week 8 (±3 days) compared to placebo.]
• Change in state anxiety score [Срок оценки: Change in State-Trait Anxiety Inventory - State version (STAI-S) total score from baseline to week 8 compared to placebo.]
• Change in severity of gastro-intestinal symptoms [Срок оценки: Change from baseline in gastro-intestinal severity score at Week 5 and Week 8 compared to placebo]
• Incidence of treatment-emergent adverse events (Safety and Tolerability) [Срок оценки: From baseline through the 8-week intervention period.]