The self-help book used in this study was independently developed by members of our research team. Its content is based on Exposure and Response Prevention (ERP). Adolescent patients with OCD will be instructed to read one chapter of the self-help book each week and complete the corresponding exercises. This 12-week intervention will involve self-guided practice conducted by the adolescent and their family members.Throughout the intervention period, adolescents and their caregivers may contact the therapist via WeChat to ask questions and upload records of their completed exercises. The therapist will respond to any questions within 48 hours by sending written messages via WeChat, with each family receiving no more than 30 minutes of such written guidance per week. All therapists will be required to keep a weekly log of the time spent providing guidance to each participating family.If a participating family does not initiate contact, the therapist will not provide proactive guidance.

The Obsessive-Compulsive Inventory-Child Version (OCI-CV) is a multidimensional self-report scale developed by Foa and colleagues to assess the severity of obsessive-compulsive symptoms in children and adolescents aged 7 to 17. The scale consists of 21 items covering six symptom dimensions: Doubting/Checking, Obsessing, Hoarding, Washing, Ordering, and Neutralizing. Each item is rated on a 3-point Likert scale: 0 = Never, 1 = Sometimes, 2 = Always. The Chinese version of the scale used in current study has demonstrated strong psychometric properties and has been validated in international clinical samples. The internal consistency of the total scale was 0.856, and the internal consistency coefficients for the subscales ranged from 0.462 to 0.747. Test-retest reliability coefficients ranged from 0.532 to 0.758.The outcome is measured by the change in total score from baseline.

The Screen for Child Anxiety Related Emotional Disorders (SCARED) is a self-report screening tool developed to assess anxiety symptoms in children and adolescents aged 9 to 18. It is widely used in clinical settings, research, and epidemiological studies as a supplemental tool for the diagnosis of anxiety-related disorders. The SCARED scale assesses five factors: somatization, generalized anxiety, separation anxiety, social phobia, and school phobia. Items are rated on a 3-point Likert scale: 0 = not true or hardly ever true, 1 = somewhat true or sometimes true, and 2 = very true or often true.

The psychometric properties of the Chinese version used in the present study include test-retest reliability coefficients ranging from 0.567 to 0.608, split-half reliability of 0.88, and Cronbach's alpha coefficients ranging from 0.43 to 0.89. Item-total correlations ranged from 0.43 to 0.74.

The Clinical Global Impression (CGI) scale is a clinician-rated tool commonly used in psychiatric treatment studies to subjectively assess the severity of illness, treatment response, and overall therapeutic efficacy. It was developed by the Early Clinical Drug Evaluation Program (ECDEU) research group for clinical trials sponsored by the National Institute of Mental Health (NIMH). The CGI provides a clinician-based evaluation framework for determining the severity of a patient's symptoms and monitoring treatment progress over time. The CGI-I is used to assess overall improvement relative to baseline, scored from 1 (very much improved) to 7 (very much worse).

The CGI-S is a clinician-rated measure of the severity of the patient's illness, scored from 1 (normal) to 7 (among the most extremely ill).

The scale was developed to assess functional impairments specifically resulting from OCD. It consists of two versions: a child self-report and a parent-report, which differ only in pronoun usage ("you" for the child version; "your child" for the parent version).The instrument includes 33 items.Each item is rated on a 4-point Likert scale, where 0 indicates "no interference" and 3 indicates "severe interference." Higher total scores reflect greater functional impairment due to OCD symptoms. The original versions of both the parent and child reports demonstrated good internal consistency (Cronbach's alpha = 0.83-0.91 for the parent version; 0.78-0.92 for the child version) and test-retest reliability (Intraclass Correlation Coefficient = 0.81 for the parent version; 0.89 for the child version).The outcome is measured by the change in total score from baseline.

The Parenting Stress Index-Short Form (PSI-SF) was developed to assess the level of parenting stress experienced by parents of children. The scale consists of three subscales: Parental Distress, Parent-Child Dysfunctional Interaction, and Difficult Child, with each subscale comprising 12 items, for a total of 36 items.Items are rated on a 5-point Likert scale ranging from 1 ("Strongly Disagree") to 5 ("Strongly Agree"). The total score ranges from 36 to 180, with higher scores indicating greater parenting stress.Based on the total score, parenting stress is categorized into four levels: scores ≤85 indicate a normal range, 86-90 indicate a borderline level, 91-98 indicate a high level, and scores ≥99 reflect a very high level of stress. A total score above 90 suggests the need for psychological support from a mental health professional.The outcome is measured by the change in total score from baseline.

This scale is designed to assess the quality of life of family caregivers. It consists of 16 items covering four dimensions: physical, social, spiritual, and psychological well-being. Each item is rated on a 5-point Likert scale ranging from 1 ("Strongly Disagree") to 5 ("Strongly Agree"). Total scores range from 16 to 80, with higher scores indicating better quality of life among caregi is designed to assess the quality of life of family caregivers.The Chinese version used in the current study also showed good reliability and validity, with a Cronbach's α of 0.84.

The study designs a self-rated questionnaire about cost-effectiveness analyses, including both direct and indirect costs, and the caregivers of the patients fill out the questionnaire based on the bill. The cost-effectiveness analysis method (CEA) is used to measure the spending of three groups. The results of the total cost divided by CY-BOCS total reduction scores can reflect the cost required to obtain each unit of curative effect.

Dropout rate is recorded to evaluate treatment acceptability.

Homework completion is recorded to evaluate treatment acceptability. The investigators use sign-in sheets to keep track of patients' homework completion.

Subjective satisfaction with treatment is recorded to evaluate treatment acceptability. The investigators use a self-rated question（"Overall, how satisfied are you with your current treatment?") to measure patients' subjective satisfaction. The rating was done on a 7-item scale ranging from "Extremely dissatisfied" to "Extremely satisfied".

Adverse events (AEs) are the treatment safety indicators.

The University of Rhode Island Change Assessment (URICA) is a self-report measurement method developed by McConnaughy, DiClemente, Prochaska, and Velicer . The 24-item version consists of four dimensions: Precontemplation (Cronbach's α = 0.79), Contemplation (Cronbach's α = 0.84), Action (Cronbach's α = 0.84), and Maintenance (Cronbach's α = 0.82). URICA is commonly used to study motivation related to the treatment of behavioral health issues, and few studies have explored the specific relationship between the URICA scales and Cognitive Behavioral Therapy (CBT) for obsessive-compulsive disorder.For the general population, the following cut-off scores may be appropriate: 8 or lower classified as People in Precontemplation 8-11 classified as People in Contemplation 11-14 classified as People in Preparation or Action For intensive service populations, it may be more appropriate to use only score in the range of 12-14 to classify those in preparation and action.

The full name of the self-completed Six-Dimension Health Survey Brief Form (SF-6Dv2) is "Short Form Six-Dimensions version 2". The SF-6Dv2 is an updated version of the widely used SF-36 Health Survey Questionnaire. It is a health utility measurement tool used to assess an individual's health-related quality of life (HRQoL) and convert it into health utility values, which can be used to calculate Quality Adjusted Life Years (QALYs). The SF-6Dv2 includes six dimensions: physical function, role limitation, social function, pain, mental health, and vitality.

The cost-utility analysis method is used to measure the spending of improving patients' quality of life. The results of the total cost divided by SF-6Dv2 total improvement scores can reflect the cost required to obtain each unit of utility.

The investigators will use the Go/No-Go and Flanker task as electroencephalography (EEG) task paradigms to assess the neuroelectrophysiological changes cauesd by self-help intervention in adolescents patients with OCD.

The investigators will use structural and functional magnetic resonance imaging (MRI) to assess the neurophysiological changes cauesd by self-help intervention in adolescents patients with OCD.