Quality control protocol of the National Mental Health Survey-2 of India.

The National Mental Health Survey of India - 2 (NMHS-2), currently underway (2024-26), is one of the largest psychiatric epidemiological studies globally, interviewing more than 250,000 individuals across all 36 states and union territories. Given India's scale and diversity, a rigorous quality control (QC) protocol has been developed to ensure methodological fidelity, data reliability, and operational consistency. Designed through iterative consultations with national and international experts, and approved by the National Technical Advisory Group, the protocol leverages lessons from NMHS-1 and integrates global best practices to meet India's unique challenges. This protocol aims to describe the QC framework of NMHS-2, highlighting its design, core components, and implementation strategies. Key components include a multi-tiered administrative structure, systematic instrument selection, its validation and translation; structured training programs for field data collectors; and pre-survey pilot testing of the sampling design. The critical Core QC strategy involves a custom-made digital data collection platform with built-in logic checks, real-time dashboards, multi-source data verification, and re-interviews, apart from standardized data cleaning protocols. Comprehensive documentation and regular review meetings at both state and central levels further strengthen accountability and transparency. By integrating international standards with locally tailored approaches, NMHS-2 establishes a replicable model for quality assurance in large-scale mental health surveys. This paper addresses a critical gap in the literature on structured QC protocols for psychiatric epidemiological studies.