In the transition between the 19th and 20th centuries, Brazilian national identity and social thought were shaped considering the spatial and symbolic dichotomy of coast-sertão, with active involvement from psychiatry. However, in the realm of racialist theories studies, these aspects have not been adequately correlated by social sciences and remain generally absent in the interdisciplinary field of mental health. In this article, we explore the significance of the sertão subregion in the Northeast in Brazilian scientific research concerning the history of mental health from the late 19th century until 1940. This specific time frame was chosen considering the relevant period of the violent epistemologies prevalent during that period and the scarcity of scientific literature on this subject. Three academic repositories from two leading institutions in the field of health were analyzed, the Oswaldo Cruz Foundation and the University of São Paulo, while the method and analysis were inspired by postcolonial perspectives, collaborative and non-extractive methodologies of southern epistemologies, and critical social psychology. As a review study, a thematic matrix was developed with three categories of analysis—postcolonial studies, Northeast and sertão; racialism and mental health; epistemic justice—and ten topics, in addition to a documentary matrix. The results indicated a scarcity of scientific productions on the Northeast and its sertão subregion, which we refer to as an epistemic invisibility, configuring it as an epistemic south. The originality of the study lies precisely in the method used to analyze academic productions on the sertão, shedding light on intersectional and interdisciplinary debates in health. It brings this territory to the forefront beyond the southeastern axis (Rio de Janeiro-São Paulo, the epistemic center of the history of mental health), and thus democratizing the understanding of the construction of Brazilian identity by emphasizing the role of psychiatry and its lasting effects to generate epistemic justice. Finally, impactful and collaborative actions were recommended to promote studies in this field, updating the relevance of the sertão and highlighting the racist and regionalist foundations ingrained in the construction of knowledge.