The goal of this clinical trial is to evaluate the efficacy and influencing factors of the combination of the anterior limb of internal capsule and nucleus accumbens (ALIC-NAc) deep brain stimulation (DBS) in patients with treatment-refractory obsessive-compulsive disorder (OCD). The main questions it aims to answer is:

Does the timing of DBS activation (at 1, 2, or 3 months post-surgery) affect the reduction rate in Y-BOCS scores? Researchers will compare three groups-DBS activated at 1, 2, and 3 months post-surgery-to determine whether earlier or later stimulation leads to greater symptom improvement.

Participants will:

• Undergo surgical implantation of an intracranial neurostimulation system targeting ALIC-NAc
• Be randomly assigned to one of three DBS activation timing groups
• Receive regular clinical assessments over a 6-month follow-up period after activation

This trial adopted a prospective, multicenter, randomized, open-label, parallel-group design. The study population comprised patients with treatment-refractory obsessive-compulsive disorder whose symptoms could not be effectively controlled by pharmacotherapy and psychotherapy. After providing informed consent, participants underwent implantation of an intracranial neurostimulation system, followed by scheduled activation of stimulation post-surgery.

A total of 60 patients were planned for enrollment and randomly assigned to one of three groups based on the timing of stimulation initiation: the one-month group (activation at 30 ± 7 days post-surgery), the two-month group (activation at 60 ± 7 days), and the three-month group (activation at 90 ± 7 days), with 20 participants in each group (1:1:1 allocation). Participants followed the trial schedule for regular assessments. The primary outcome was the difference in Y-BOCS reduction rates among the three groups at 90 ± 7 days after stimulation initiation.

Inclusion Criteria:

• aged 18-65 years old;

• a diagnosis of OCD based on The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5);

• the Y-BOCS total score ≥ 25;

• met the criteria of treatment refractory. Treatment refractory is defined as failed a) Inadequate response or intolerance to at least three adequate trials of selective serotonin reuptake inhibitors (SSRIs), combined with at least two second-generation antipsychotics as augmentation agents.

  b) Inadequate response or intolerance to cognitive behavioral therapy (CBT) consisting of more than 12 sessions conducted concurrently with adequate dosed SSRIs treatment.

Exclusion Criteria:

• Presence of other psychiatric disorders such as organic mental disorders, paranoid personality disorder, or mental retardation.
• Individuals deemed by the investigator to be at significant risk of suicidal behavior based on clinical assessment.
• Presence of severe or unstable cardiovascular, respiratory, hepatic, renal, hematologic, endocrine, neurological, or other systemic diseases.
• History of organic brain disorders, traumatic brain injury, intractable epilepsy, or other neurological conditions.
• Clinically significant abnormalities in physical examination, laboratory tests, electrocardiogram, or imaging during screening or baseline that, in the investigator's judgment, make the individual unsuitable for the study.
• History of implantation of a cochlear implant, cardiac pacemaker, cardiac defibrillator, prior unilateral or bilateral implantation of similar devices, or other surgical procedures within the past six months that may affect study participation as judged by the investigator.
• Contraindications to DBS implantation or deemed unfit for surgery by the investigator.
• Confirmed HIV-positive status.
• Pregnant or breastfeeding women, women of childbearing potential with positive blood/urine HCG results at screening, those unable to use effective contraception during the study, or those planning to conceive within three months after study initiation.
• Participation in another drug or medical device clinical trial currently or within three months prior to screening.
• Any other condition deemed by the investigator to render the individual unsuitable for the study.