Transdiagnostic findings across major depressive disorder, bipolar disorder and schizophrenia: A qualitative review

This narrative review examines the growing body of research highlighting the transdiagnostic features of Major Psychoses, encompassing Major Depressive Disorder (MDD), Bipolar Disorder (BD), and Schizophrenia (SZ). Overlapping genetic, psychosocial risk factors, neuroimaging, cognition, course of illness, treatments and psychopathological domains challenge the traditional categorical distinctions that have long defined these disorders. Evidence reveals shared variance in these domains. Furthermore, dimensional approaches, such as the Research Domain Criteria (RDoC), Hierarchical Taxonomy of Psychopathology (HiTOP), network approaches and clinical staging, offer frameworks for understanding these disorders along a continuum rather than within rigid categorical boundaries. This review synthesizes current empirical findings across these domains and emphasizes the need for a re-evaluation of psychiatric classification systems. It argues that a transdiagnostic approach may lead to more explained variance in clinical and neurobiological research, personalized as well as effective diagnostic and treatment strategies, ultimately improving patient outcomes.