Supplementary Material for: What is mental pain? A systematic review and metasynthesis of qualitative research on the lived experience of mental pain

Introduction: Mental pain—a pain not primarily felt in the body—is a predictor of suicide and is often described as one of the most distressing aspects of depression. However, the absence of a clear definition hampers both research and clinical practice. This metasynthesis aims to characterize the lived experience of mental pain to inform the future development of a definition. Methods: We conducted a systematic search in MEDLINE, EMBASE, PsycINFO, CINAHL, and Web of Science to identify qualitative studies reporting first-person accounts of mental pain. Thematic synthesis was used to generate descriptive and analytical themes, drawing on semantic, clinical, and phenomenological insights. The quality of the primary studies was assessed using the Critical Appraisal Skills Programme (CASP), and the Confidence in the Evidence from Reviews of Qualitative Research (GRADE-CERQual) approach was applied to evaluate the findings. Results: The metasynthesis included 49 qualitative studies with 1,467 participants and led to the development of 22 themes and 85 subthemes. Mental pain was defined by five phenomenal features: unpleasant, immediate, identity-disrupting, invisible, and often perceived as worse than physical pain. It is also accompanied by unspecific psychological and physical manifestations. The emergence of mental pain can be conceptualized as a signal of a threatened sense of self in response to bodily, psychological, existential, or social adversity. Confidence in the findings was moderate due to methodological and reporting limitations. Conclusion: A clearer understanding of mental pain may enhance clinical practice by helping clinicians better identify, understand, and respond to this form of suffering.