Department of Nursing;
Xi'an Jiaotong University Health Science Center;
Xi'an;
Shaanxi 710061;
China;
Department of Epidemiology and Biostatistics;
School of Public Health;
Xi'an]iaotong University Health Science Center;
Xi'an;
Shaanxi 710061;
China;
Xi'an Center for Disease Control and Prevention;
Xi'an;
Shaanxi 710054;
China;
Perceived social support; Retention; Methadone; Maintenance treatment; Relationship;