This randomized, double-blind, sham-controlled clinical trial will evaluate whether individualized alpha-frequency transcranial alternating current stimulation (tACS) can enhance the effects of mindfulness therapy in adults with generalized anxiety disorder. A total of 99 participants will be randomly assigned to one of three groups: synchronous tACS combined with mindfulness therapy, desynchronous tACS combined with mindfulness therapy, or sham tACS combined with mindfulness therapy.

All participants will receive a standardized mindfulness therapy program. The study will compare changes in anxiety symptoms, worry, mindfulness, attention control, cognitive performance, and neurophysiological measures across the three groups. Assessments will be conducted from baseline through follow-up visits to examine both clinical effects and possible neural mechanisms.

Generalized anxiety disorder is characterized by excessive and difficult-to-control worry, often accompanied by physical symptoms and impaired daily functioning. Mindfulness-based therapy may help patients observe worry and anxiety-related bodily sensations with greater awareness and acceptance. Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that may modulate neural oscillations related to cognitive control and emotion regulation.

This study will enroll 99 adults with generalized anxiety disorder. Eligible participants will be randomly assigned in a 1:1:1 ratio to one of three intervention groups: synchronous tACS plus mindfulness therapy, desynchronous tACS plus mindfulness therapy, or sham tACS plus mindfulness therapy. All groups will receive the same standardized mindfulness therapy program. The active tACS conditions will target the frontoparietal network, with stimulation parameters individualized according to each participant's alpha-band neurophysiological characteristics. The sham stimulation condition will mimic the initial and final sensation of stimulation while delivering no active current during the main stimulation period.

Clinical, behavioral, and neurophysiological assessments will be collected at baseline and follow-up visits. Outcome assessments will include anxiety severity, depressive symptoms, worry, mindfulness, attention control, cognitive performance, adverse effects related to tACS, and multimodal measures such as electroencephalography, magnetic resonance imaging, and eye tracking. The study aims to determine whether individualized alpha-frequency tACS can improve the therapeutic effects of mindfulness therapy and to explore potential neural mechanisms underlying treatment response.

Inclusion Criteria:

• Outpatients or inpatients of The Second Xiangya Hospital of Central South University.
• Diagnosis of generalized anxiety disorder as the primary diagnosis according to the International Classification of Diseases 11th Revision (ICD-11) diagnostic criteria, confirmed by two experienced psychiatrists.
• Hamilton Anxiety Rating Scale (HAMA) total score of 14 or higher.
• Aged 18 to 60 years, inclusive.
• Right-handed.
• Junior high school education or above, with sufficient ability to understand the study procedures, complete informed consent, clinical scales, and cognitive assessments.
• Currently not using anxiolytic or antidepressant medications, or receiving a stable medication regimen for at least 1 month before enrollment, with no planned changes in the medication regimen during the 2-week treatment period unless clinically necessary.
• Voluntarily agrees to participate in the study, signs the informed consent form, and is able to comply with study visits, treatment procedures, laboratory examinations, and other study requirements.

Exclusion Criteria:

• Presence of psychotic symptoms.
• Meeting ICD-11 diagnostic criteria for schizophrenia or other primary psychotic disorders, bipolar or related disorders, current depressive episode, dysthymic disorder, or post-traumatic stress disorder currently or within the past year.
• Organic brain disease or severe physical illness, including but not limited to thyroid disease, systemic lupus erythematosus, diabetes, severe pulmonary, hepatic, or renal impairment, infection, or major trauma.
• Clinically significant uncorrectable sensory impairment, such as hearing impairment that prevents effective communication.
• Pregnancy or lactation.
• Contraindications to transcranial electrical stimulation or related procedures, including metal implants in the body, intracranial hypertension, skull defects, brain tumor, severe heart disease, unstable vital signs due to serious physical illness, acute cerebrovascular disease, or a history of adverse reactions to electrical stimulation.
• Any other condition that, in the investigator's judgment, makes the participant unsuitable for this study.

Participants and outcome assessors will be masked to group assignment. Sham stimulation will include 30-second ramp-up and ramp-down periods at the beginning and end of stimulation to mimic the sensation of active tACS, while no active current will be delivered during the main 20-minute stimulation period. The psychotherapist, tACS operator, and data collectors will be independent research personnel, and outcome assessors will not be involved in treatment delivery.