Measurement-based care (MBC) is an evidence-based practice that incorporates routine outcome assessment using validated rating scales to guide collaborative clinical decision-making. Although MBC results in improved outcomes for patients with major depressive disorder (MDD), there are barriers to its broad implementation in clinical settings. The use of "enhanced" MBC (eMBC), with mobile apps that allow patients to track outcomes and engage in self-management via WeChat, may address some of these barriers. This study intends to compare differences of efficacy between the implementation with eMBC using WeChat and the standard MBC implementation using paper-pencil assessments at the clinic, for both implementation and clinical outcomes.

Measurement-based care (MBC) is an evidence-based practice that incorporates routine outcome assessment using validated rating scales to guide collaborative clinical decision-making. Although MBC results in improved outcomes for patients with major depressive disorder (MDD), there are barriers to its broad implementation in clinical settings. The use of "enhanced" MBC (eMBC), with mobile apps that allow patients to track outcomes and engage in self-management via WeChat, may address some of these barriers. Therefore, we present a trial protocol for a 2-arm cluster randomized controlled trial (RCT) with a hybrid implementation-effectiveness design comparing standard MBC implementation versus eMBC implementation with 6-month follow up in 12 mental health centers in Shanghai, China. The eMBC implementation uses a WeChat mini-program that includes outcome tracking using brief questionnaires and self-management lessons supplemented with support by a lay coach via WeChat. The primary implementation outcome is implementation reach, defined as the proportion of eligible patients with a PHQ-9 score recorded in the hospital chart at 6 months after MBC implementation. The primary clinical outcome is clinical remission, defined as a PHQ-9 score of 4 or less at the 6-month follow up. Other implementation and clinical outcomes will be examined, including medication adherence, doctor-patient alliance, and a piggy-back cost-benefit economic analysis. Qualitative interviews will be conducted with physicians and patients to produce an interpretive account of the contextual factors which impact eMBC implementation. This study intends to compare differences of efficacy between the implementation with eMBC using WeChat and the standard MBC implementation using paper-pencil assessments at the clinic, for both implementation and clinical outcomes.

Inclusion Criteria:

Inclusion Criteria for clinicians:

• Recruited clinicians who are on the job and they come from Shanghai Mental Health Center, the Children's Hospital of Fudan University, and Shanghai Tongji Hospital
• Recruited clinicians are of different ages, working years and genders;
• Recruited clinicians understand the research content and sign the informed consent form

Inclusion criteria for patients with MDD:

• Recruited patients should be definitely diagnosed as "MDD" in their outpatient records, and those patients are in a stable state of illness and can cooperate in completing the questionnaire survey or accepting the focus group discussion;
• Recruited patients have junior high school education or above, as well as adequate audio-visual skills, and can fully understand the informed consent form and interview content.
• The age of the recruited patients is 12-65 years, and the number of children and adolescents aged 12-18 years is not less than one third of the total sample size of patients;
• The enrolled patients or the guardian of them can understand the research content and sign the informed consent form.

Exclusion Criteria:

Exclusion criteria for clinicians:

• Recruited clinicians are unable to conduct effective verbal conversation;
• Recruited clinicians are unable to cooperate or complete other situations of the interview.

Exclusion criteria for patients with depression:

• Recruited patients who have obvious violent attacks or tendencies;
• Recruited patients who are in the attack or unstable period of illness;
• There is a serious tendency to commit suicide;
• Recruited patients who are unable to conduct effective verbal conversation;
• Recruited patients who cannot cooperate or complete other situation of the interview.

Subjects of clinicians come from Shanghai Mental Health Center, the Children's Hospital of Fudan University, and Tongji Hospital of Tongji University, whose age, working years, and gender are different.

Subjects of outpatients come from Shanghai Mental Health Center, the Children's Hospital of Fudan University, and Tongji Hospital of Tongji University who have been definitely diagnosed as MDD and are in stable condition. Their age is between 12 and 65 years old, and the number of children and adolescents aged 12 to 18 years old is not less than one third of the total sample size of patients. In addition, they have junior high school education and above, as well as adequate audio-visual skills, and can fully understand the informed consent form and interview content.