The goal of this clinical trial is to learn if metacognitive therapy can be effective in a Chinese sample of obsessive compulsive disorder (OCD) . The main questions it aims to answer are:

Can metacognitive therapy significantly reduce participants' levels of obsessive-compulsive symptoms? Can metacognitive therapy significantly improve participants' metacognitive adaptations?

The researchers will compare metacognitive therapy to a control condition without psychotherapy to see if metacognitive therapy is effective in treating OCD.

Participants will:

Receive the metacognitive therapy intervention or under control conditions for 8 to 15 weeks.

Be assessed for symptoms and metacognitive beliefs at pre-intervention, post-intervention and 12 weeks post-intervention

This study will be a randomised controlled clinical trial. Participants who meet the enrolment criteria will be randomised into an experimental group and a control group. Participants in the experimental group will receive 8-15 weeks of metacognitive therapy, while participants in the control group will receive the same amount of time of regular treatment without psychotherapy components.

The researchers will assess participants' obsessive-compulsive symptoms and metacognitive levels before, after, and 12 weeks after the intervention. Assessment measures will be the Yale Brown Obsessive-Compulsive Scale (Y-BOCS) and the Metacognition Questionnaire (MCQ-30).

By comparing the assessment results of the two groups of participants, conclusions will be drawn as to whether metacognitive therapy can have a positive effect on a Chinese OCD sample.

Inclusion Criteria:

• two psychiatrists with the title of Deputy Chief Physician or above jointly determine that the above diagnostic criteria were met
• education level of junior high school or above, without mental retardation or audio-visual disorders
• participation in the study is voluntary, and the informed consent is signed by the patient or his/her guardian

Exclusion Criteria:

• loss of or insufficient self-awareness, the presence of hallucinations, delusions, and other psychotic symptoms
• the presence of severe depression, or self-inflicted suicidal attempts and behaviors
• the presence of a history of alcohol or drug abuse
• refusal of psychotherapy, or the ineffectiveness of those who had been involved in a full course of psychotherapy.

Data might be made available to experts in the field upon request and upon the detailed description of the reason of request.

Access to data is expected to be open by 31 January 2025 and will always be continuous.

Data will be made available to experts in the field upon request and upon the detailed description of the reason of request.

The outcomes assessor is a psychiatrist who was not involved in the randomization and treatment process.