Protocol for a multicenter observational study on fatigue across physical–mental conditions within the German center for mental health

Introduction: Fatigue is a common and debilitating symptom across a wide range of chronic physical and mental health conditions. It affects physical, cognitive, and emotional functioning and substantially reduces quality of life. Despite its clinical relevance, fatigue research remains largely diagnosis-specific, resulting in limited understanding of cross-diagnostic patterns and the interplay between somatic, psychological, and psychosocial factors. Comparative data spanning different physical and mental health conditions remain limited. Objectives: This multicentre, cross-sectional observational study is designed to characterise the multidimensional profile of fatigue across seven diagnostic cohorts representing metabolic, inflammatory, oncological, neuroimmunological, post-infectious, and functional-psychosomatic conditions included in the framework of the German Center for Mental Health. Methods and analysis: Participants will complete a standardised psychometric assessment battery assessing fatigue severity, post-exertional malaise, physical functioning, and related mental-health and psychosocial variables. Key domains include depressive and anxiety symptoms, somatisation, trauma history, pain, work ability, and occupational stress. Data will be analysed descriptively and comparatively to examine shared versus condition-specific fatigue patterns within a bio-psycho-social framework. Ethics and dissemination: Ethical approval has been obtained from all participating centres prior to the conduct of the study procedures described herein, and the study is registered in the German Clinical Trials Register (DRKS00037687). Findings will be disseminated through peer-reviewed publications, conference presentations, and stakeholder networks of the German Center for Mental Health.