Transcranial Alternating Current Stimulation for Refractory Constipation With Somatic Symptom Disorder

Inclusion Criteria: 1. Diagnosis of Functional Constipation (FC): Subjects must meet the diagnostic criteria for functional constipation as defined by the Rome IV criteria. 2. Low Frequency of Complete Spontaneous Bowel Movements (CSBM): During the 2-week screening period, subjects must have ≤2 complete spontaneous bowel movements per week. 3. Poor Response to Previous Treatment: Subjects must have been dissatisfied with prior treatments for functional constipation and have undergone at least 3 months of therapy (including laxatives or other prokinetic agents). 4. Diagnosis of Somatic Symptom Disorder (SSD): Subjects must meet the DSM-5 diagnostic criteria for somatic symptom disorder (SSD). All subjects will undergo a semi-structured clinical interview based on DSM-5 criteria, conducted by professionals trained in SSD diagnosis. * Criterion A: Presence of one or more distressing somatic symptoms that significantly affect daily life. * Criterion B: At least one of the following must be met: 1. Excessive and persistent thoughts about the severity of symptoms; 2. Persistently high levels of anxiety about health or symptoms; 3. Excessive time and energy devoted to health concerns or symptoms. * Criterion C: Symptoms must persist for at least 6 months. 5. Age Range: Subjects must be between 18 and 80 years old. 6. No Concurrent Clinical Trials: Subjects must not participate in any other clinical trials during the study period. 7. Informed Consent: Subjects must voluntarily agree to participate and sign an informed consent form. Exclusion Criteria: 1. Presence of organic diseases (such as tuberculosis, polyps, Crohn's disease, tumors, congenital megacolon, etc.), endocrine disorders (e.g., hypothyroidism), metabolic diseases (diabetes, thyroid dysfunction), or neurological disorders (e.g., Parkinson's disease); 2. Long-term use of medications that may affect intestinal function or induce constipation, such as Parkinson's drugs (excluding conventional laxatives, antidiarrheals, or intestinal stimulants; during the trial, participants are only allowed to take prescribed emergency medications, with detailed records of usage required); 3. History of chronic pain or substance abuse, such as opioids; 4. Diagnosed mental disorders with psychotropic medication use for over 3 months prior to the visit, or history of psychotropic or hormonal medication use for over 3 months; 5. Individuals at risk of self-harm or suicide, as assessed by a psychiatrist, or those requiring psychosomatic intervention; 6. History of allergy to psychiatric medications (e.g., fluoxetine), or contraindications to fluoxetine such as liver/kidney impairment or prolonged Q-T interval on ECG; 7. Pregnant or breastfeeding women; 8. Patients with benign or malignant tumors or autoimmune diseases; 9. Chronic conditions requiring long-term medication that may affect quality of life or interfere with examinations/treatment, including cardiovascular diseases, coagulation disorders or regular anticoagulant use (warfarin/heparin), liver/kidney diseases, organ failure, cognitive impairment, aphasia, etc.