Background: As research on the use of mobile technology to deliver mental health support grows, the research from China is still very limited. How to design an acceptable and usable mobile mental health service model suitable for China's social and cultural environment remains to be studied.

Objective: To understand the acceptability and usability of a WeChat-based intervention among Chinese patients with depression, and to provide insights to promote future development of user-centered mobile mental health services design.

Methods: The research team developed a multi-theoretical intervention that includes seven modules: recovery lessons, recovery journal, coaching sessions, mindfulness, personalized support, regular assessments and feedback collection. Forty-two patients diagnosed with depressive disorder were recruited, with a mixed sample of patients who were using an antidepressant medication (n = 29) and patients who were not using an antidepressant medication (n = 13). A single-arm mixed-methods study was conducted to understand engagement, satisfaction, usability and potential clinical effectiveness of the intervention.

Results: There was a retention rate of 83.33% - 22 participants who used an antidepressant medication and 13 participants who did not use an antidepressant medication completed the final assessments. The median (upper quartile-lower quartile) of the completed 60 recovery journals and 7 coaching sessions was 56 (59-46) and 6 (7-4) times, respectively. Participants' satisfaction regarding their recovery progress, and on perceived helpfulness on different modules were high. The overall score of the user version of the Mobile Application Rating Scale was 4.23 (SD 0.44, range 1-5), indicating high acceptability and usability. Qualitative feedback identified three key themes: an efficient access to professional help, a personalized source of social support, and a facilitator of cognitive and behavioral change.

Conclusions: This study demonstrated that a WeChat-based intervention for depression was acceptable, and has the potential to promote personal recovery. More studies are needed to understand the efficacy and implementation of this model in real world.