In the previous issue, Muneer and Mazommi systematically reviewed clinical staging models of major mood disorders and their associated clinical and neurobiological correlates [3]. Several assumptions must be made to create a useful staging model for a particular disease. First, the natural history of the disorder must be predictable. Second, stage-appropriate treatment must be capable of influencing disease progression. Third, earlier diagnosis and management must afford a favorable prognosis. Last, early intervention can change stage development over time. A great deal of research has allowed us to understand the natural history and pathogenetic mechanisms of many major psychiatric disorders; various novel treatments improve long-term prognoses. Moreover, studies on the premorbid and prodrome stages of psychiatric disorders have shed light on useful preventative approaches. Based on these efforts, the clinical staging of major psychiatric disorders has improved greatly [1,2].

However, the basis of clinical staging remains of concern. The boundaries of psychiatric disorders shift because of heterogeneity within single diagnostic entities, such that both the clinical course and outcome are unpredictable. Transdiagnostic similarities are also prevalent. As the early stage clinical phenotypes of many mental disorders overlap substantially, lumping rather than splitting during staging has been suggested [4]. In the bipolar disorder staging model, the phenotypes of chronic disabilities based on the neuroprogression model related to allostatic load [5,6] overlap with those of chronic severe schizophrenia [7,8]. The chronic refractory states of several psychiatric disorders show similarity in such transdiagnostic features [7,8].

The categorical diagnostic system has gradually been superseded by the spectrum model of psychiatric disorders. The bipolar spectrum is a widely accepted concept [9]. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) introduced the spectral representation of autism and substance abuse [10]. The spectrum approach facilitates a dimensional understanding of psychiatric disorders. Single diagnostic entities could be supplanted by a more flexible continuum that considers multiple factors. A staging system provides a heuristic framework for research on psychiatric disorders and appropriate clinical practice; use of an integrated dimensional spectral approach toward psychiatric disorders could assist the construction of appropriate staging systems [11].