The GREENBEAN checklist for reporting studies evaluating the effectiveness of EEG-based biomarkers.

Advances in digital technology, signal analysis, and data science have led to a rapid increase in papers reporting EEG-based biomarkers. However, wide heterogeneity in study design and reporting poses challenges in assessing the reliability, validity and utility of these biomarkers. In this evolving field, best practices are sometimes debated but not yet rigorously defined, and the appropriate next step is to ensure that validation-focused research manuscripts report key methodological factors that are known or suspected to influence results. To assist authors in designing and reporting validation studies of EEG biomarkers, and to help editors and regulatory bodies evaluate them, an international working group-under the auspices of the International Federation of Clinical Neurophysiology (IFCN) and in collaboration with the EQUATOR Network-developed the Guidelines for Reporting EEG/Neurophysiology Biomarker Evaluation for Application to Neurology and Neuropsychiatry (GREENBEAN). EEG biomarker validation studies are classified into four phases, similarly to therapeutic studies. Phases 1-2 are preliminary and do not constitute formal validation. Phase 3 studies provide compelling evidence of validity, while phase 4 studies assess the clinical utility and generalizability of previously validated biomarkers within real-world settings. We provide detailed definitions for each phase, along with a checklist of items to address and report. A detailed Explanation and Elaboration document is included in Supplementary Material with multiple examples of how to design and report EEG biomarker studies. We expect that more transparent reporting regarding experimental design and technical standards will not only enhance short-term biomarker validation efforts but will also enhance methodological research to make future efforts more efficient and effective.