Background Obsessive-compulsive disorder (OCD) is a common and chronic mental illness with a high rate of disability. Internet-based cognitive behavioral therapy (ICBT) makes online treatment available to patients and has been shown to be effective. However, 3-arm trials on ICBT, face-to-face cognitive behavioral group therapy (CBGT), and only medication are still lacking. Objective This study is a randomized, controlled, assessor-blinded trial of 3 groups for OCD: ICBT combined with medication, CBGT combined with medication, and conventional medical treatment (ie, treatment as usual [TAU]). The study aims to investigate the efficacy and cost-effectiveness of ICBT related to CBGT and TAU for adults with OCD in China. Methods In total, 99 patients with OCD were selected and randomly assigned to the ICBT, CBGT, and TAU groups for treatment for 6 weeks. The primary outcomes were the Yale-Brown Obsessive-Compulsive Scale (YBOCS) and the self-rating Florida Obsessive-Compulsive Inventory (FOCI), compared at baseline, during treatment (3 weeks), and after treatment (6 weeks), to analyze efficacy. The secondary outcome was the EuroQol Visual Analogue Scale (EQ-VAS) scores of the EuroQol 5D Questionnaire (EQ-5D). The cost questionnaires were recorded to analyze cost-effectiveness. Results Repeated-measures ANOVA was used for data analysis, and the final effective sample size was 93 (ICBT: n=32, 34.4%; CBGT: n=28, 30.1%; TAU: n=33, 35.5%). After 6-week treatment, the YBOCS scores of the 3 groups significantly decreased (P<.001), and there were no significant differences among groups. The FOCI score of the ICBT (P=.001) and CBGT (P=.035) groups was significantly lower than that of the TAU group after treatment. The total cost of the CBGT group (renminbi [RMB] 6678.45, 95% CI 4460.88-8896.01 [US $1010.36, 95% CI 678.87-1345.84]) was significantly higher than that of the ICBT group (RMB 3308.81, 95% CI 2476.89-4140.73[US $500.58, 95% CI 374.72-626.43], P<.001) and the TAU group (RMB 2259.61, 95% CI 2074.16-2445.05 [US $341.85, 95% CI 313.79-369.90], P<.001) after treatment. The ICBT group spent RMB 303.19 (US $45.97) less than the CBGT group and RMB 11.57 (US $1.75) less than the TAU group for each unit reduction in the YBOCS score. Conclusions Therapist-guided ICBT combined with medication is as effective as face-to-face CBGT combined with medication for OCD. ICBT combined with medication is more cost-effective than CBGT combined with medication and conventional medical treatment. It is expected to become an efficacious and economic alternative for adults with OCD when face-to-face CBGT is not available. Trial Registration Chinese Clinical Trial Registry ChiCTR1900023840; https://www.chictr.org.cn/showproj.html?proj=39294

BACKGROUND Obsessive-Compulsive Disorder (OCD) is a common and chronic mental illness with a high rate of disability. Internet-based Cognitive Behavioral Therapy (ICBT) makes online treatment available to patients, and has been shown to be effective. However, three arm trials on ICBT, face-to-face group CBT, and medication only were still lacking. OBJECTIVE The study was a randomized, controlled, assessor-blinded trial of three groups in the obsessive-compulsive disorder: Internet-based Cognitive Behavioral Therapy (ICBT) combined with medication, Cognitive Behavioral Group Therapy (CBGT) combined with medication, and conventional medical treatment (i.e. treatment as usual, TAU). The study aimed to investigate the efficacy and cost-effectiveness of ICBT related to CBGT and TAU for adults with OCD in China. METHODS 99 OCD patients were selected and randomly assigned to the ICBT group, CBGT group, and TAU group for treatment of 6 weeks in the study. The primary outcomes were the Yale-Brown Obsessive-Compulsive Scale (YBOCS) and self-rating Florida Obsessive-Compulsive Inventory (FOCI), compared at baseline, during treatment(3-week), and after treatment(6-week) to analyze efficacy. The secondary outcome was the EQ-VAS scores of the EuroQol five-dimensional questionnaire (EQ-5D). The cost questionnaires were recorded to analyze the cost-effectiveness. RESULTS Repeated measures analysis of variance (ANOVA) was used for data analysis, and the final effective data was 93 (ICBT=32, CBGT=28, TAU=33). After 6-week treatment, the YBOCS scores of three groups significantly decreased (P<.001), and there was no significant differences among groups. The FOCI score of the ICBT group (P =.001) and CBGT group (P =.035) were significantly lower than that of the TAU group after treatment. The total cost of the CBGT group (6678.45 (95%CI 4460.88-8896.01) RMB ($1010.36 (95%CI 678.87-1345.84) USD)) was significantly higher than that of the ICBT group (3308.81 (95%CI 2476.89-4140.73) RMB ($500.58 (95%CI 374.72-626.43) USD)) (P<.001) and the TAU group (2259.61 (95%CI 2074.16-2445.05) RMB ($341.85 (95%CI 313.79-369.90) USD)) (P<.001) after treatment. The ICBT group spent 303.19 ($45.97 USD) RMB less than the CBGT group and 11.57 ($1.75 USD) RMB less than the TAU group for each unit YBOCS reduction score. CONCLUSIONS Therapist-guided ICBT for OCD was as effective as face-to-face group CBT and medication therapy, and was more cost-effective. It is expected to become one way to improve the treatment effect of patients with OCD. CLINICALTRIAL Clinical Trial Registry ChiCTR1900023840; http://www.chictr.org.cn/index.aspx