Inclusion Criteria:
1. Male or female subjects aged 18-65 years
2. Meeting the diagnostic criteria for tension-type headache (TTH) according to ICHD-3; with ≥6 but \<15 attack days per month in the past 3 months and MIDAS score \>21; onset of TTH before age 50, with a history exceeding 1 year
3. Informed consent obtained from the patient
Exclusion Criteria:
1. History of allergy to Desvenlafaxine, or use of Desvenlafaxine within 4 weeks prior to the start of the treatment period; currently taking or requiring concomitant administration of drugs contraindicated in the package insert, such as monoamine oxidase inhibitors (MAOIs);
2. Diagnosable with chronic tension-type headache or medication overuse headache;
3. Comorbid with other types of headaches, such as trigeminal autonomic cephalalgias, migraine attacks \>1 time/month within 3 months, or secondary headaches (e.g., those caused by intracranial infections, craniocerebral trauma, cerebrovascular diseases);
4. Severe psychiatric disorders such as schizophrenia, moderate to severe anxiety-depression (Hamilton scale ≥12 points); poorly controlled epilepsy, cognitive impairments, and other chronic pain conditions; serious organic diseases that pose significant health risks, including uncontrolled hypertension, cardiac disease, hepatic dysfunction, renal insufficiency, infections; any medical condition or prior surgery likely to affect the absorption, metabolism, or excretion of the study drug;
5. Concomitant use of venlafaxine analogues such as serotonin-norepinephrine reuptake inhibitors (SNRIs); unstable use of other preventive medications for TTH, including amitriptyline, mirtazapine (≤3 months); discontinuation of currently reported effective prophylactic drugs or overused analgesics for ≥3 months may allow re-enrollment;
6. Alcohol dependence or substance abuse;
7. Inability to comprehend the study protocol due to low education level, impaired verbal/language function, visual or auditory deficits; failure to accurately complete research materials like headache diaries or cooperate with scale assessments;
8. Women who are planning pregnancy, pregnant, breastfeeding, or not using contraception;
9. Participation in other interventional clinical studies that may influence outcome evaluations.
