The central WMH staff trained bilingual supervisors in each country. Consistent interviewer training documents and procedures were used across surveys. The WHO translation protocol was used to translate instruments and training materials. Standardized descriptions of the goals and procedures of the study, data uses and protection, and participants' rights were provided in written and verbal form to all respondents before verbal informed consent was secured. Quality control protocols were standardized across countries to check on interviewer accuracy and to specify data cleaning and coding procedures. The institutional review board of the organisation that coordinated the survey in each country approved and monitored compliance with procedures for obtaining informed consent and protecting participants. A more detailed discussion of these procedures is presented elsewhere [27,30].
