Objective: This study aims to evaluate the effectiveness of Bacillus coagulans in improving anxiety and depression in patients diagnosed with functional dyspepsia according to the Rome IV criteria.

Methods: This trial plans to enroll 180 patients (90 per group). The study will employ a double-blind design. For patients diagnosed with FD according to the Rome IV criteria, in addition to conventional treatment (treated with Mosapride Citrate Tablets (Guangdong Anno Guocai) for Postmeal Discomfort Syndrome (PDS) and Esomeprazole Enteric Coated Tablets (Shijiazhuang Longze Pharmaceutical Guocai) for Upper Abdominal Pain Syndrome (EPS)), the experimental group was treated with Bacillus coagulans, while the control group received a placebo with the same appearance and odor.

The treatment intervention will last for 4 weeks. The main indicator of this experiment is the improvement of the Hospital Anxiety and Depression Scale (HADS score) after 4 weeks of treatment. The secondary indicators are the improvement rate of the overall treatment effectiveness evaluation questionnaire (OTE questionnaire), the improvement of the global overall symptom score (GOS score), the improvement of the simplified Nipin scale (SF-NDI), and the improvement of the Pittsburgh Sleep Index (PSQI) after 4 weeks of treatment. Upon completion of the trial, the patients' conditions will be re-evaluated, and treatment plans will be adjusted accordingly.

Inclusion Criteria:

• Patients diagnosed with functional dyspepsia (FD) according to the Rome IV criteria.
• Aged 18 to 80 years, regardless of gender.
• Hospital Anxiety and Depression Scale (HADS) score between 8 and 14.

Exclusion Criteria:

• Use of probiotics or antibiotics within one month prior to the trial.
• Use of psychoactive medications (including hypnotics, sedatives, anxiolytics, or antidepressants) within one month prior to the trial.
• Use of hormones, immunosuppressants, or cytotoxic agents within one month prior to the trial.
• Participation in any other clinical trial within one month prior to the study.
• Positive test for Helicobacter pylori (Hp) infection.
• Long-term use of traditional Chinese herbal medicine.
• Pregnancy or lactation.
• History of drug abuse.
• Comorbidities such as irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), functional constipation (FC), or other significant conditions that may interfere with the trial-including severe hepatic, renal, respiratory, or autoimmune disorders; bleeding diatheses; psychiatric diseases; endocrine disorders; etc.
• History of major surgery or diagnosis of diabetes mellitus.
• Refusal to provide written informed consent.