Here, we have utilised the concept of fuzzy logic and Karl Popper’s notion of verisimilitude to advocate navigating the complexity of psychiatric nosology, emphasising that psychiatric disorders defy Boolean logic. We underscore the importance of embracing imprecision and collecting extensive data for a more nuanced understanding of psychiatric disorders, asserting that falsifiability is crucial for scientific progress. We encourage the advancement of personalised psychiatric taxonomy, urging the continual accumulation of data to inform emerging advancements like artificial intelligence in reshaping current psychiatric nosology.

More than 10 years prior to the anticipated 2013 publication of DSM-5, processes were set in motion to assess the research and clinical issues that would best inform future diagnostic classification of mental disorders. These efforts intended to identify the clinical and research needs within various populations, examine the current state of the science to determine the empirical evidence for improving criteria within and across disorders, and stimulate research in areas that could potentially provide evidence for change. In the second phase of the revision process, the American Psychiatric Institute for Research and Education (APIRE) recently completed the 5-year international series of 13 diagnostic conferences convened by APA/APIRE in collaboration with the World Health Organization and the National Institutes of Health (NIH), under a cooperative grant funded by the NIH. From these conferences, the DSM-5 Task Force and Work Groups have developed plans for potential revisions for DSM-5, including the incorporation of dimensional approaches within and across diagnostic groups to clarify heterogeneity, improve diagnostic validity, and enhance clinical case conceptualization. Use of dimensions for measurement-based care has been shown to be feasible in psychiatric and primary care settings and may inform monitoring of disorder threshold, severity, and treatment outcomes. The integration of dimensions with diagnostic categories represents an exciting and potentially transformative approach for DSM-5 to simultaneously address DSM-IV's clinical short-comings and create novel pathways for research in neurobiology, genetics, and psychiatric epidemiology.

This review seeks to determine the degree to which modern operationalized diagnostic criteria for mania reflect the clinical features of mania described historically by expert textbook authors. Clinical descriptions of mania appearing in 18 textbooks published between 1899 and 1956 were reviewed and compared to the criteria for mania from six modern operationalized diagnostic systems. Twenty-two prominent symptoms and signs were reported by five or more authors. Two symptoms (elevated mood and grandiosity) and four signs (hyperactivity, pressured speech, irritability, and new activities with painful consequences) were reported by every author. A strong relationship was seen between the frequency with which the clinical features were reported and the likelihood of their inclusion in modern diagnostic systems. However, many symptoms and signs including impulsivity, hypersexuality, mood lability, altered moral standards, increased humor, hypergraphia, and a vigorous physical appearance were not included in any modern criteria. Indeed, DSM-5 contains only eight of the historically noted clinical features. We conclude that modern operationalized criteria for mania well reflect symptoms and signs frequently reported by historical experts. This suggests that the clinical construct of mania has been relatively stable in western Psychiatry since the turn of the 20th century. However, many useful clinical features of mania described in these textbooks are missing from these criteria thereby illustrating the limitations of clinical evaluations restricted to the assessment of only current diagnostic criteria. The disorders we study and treat are considerably richer clinically than is reflected in the DSM criteria which we use to diagnose them.

Much has changed since the two dominant mental health nosological systems, the International Classification of Diseases (ICD) and the Diagnostic and Statistical Manual of Mental Disorders (DSM), were first published in 1900 and 1952, respectively. Despite numerous modifications to stay up to date with scientific and cultural changes (eg, exclusion of homosexuality as a disorder) and to improve the cultural sensitivity of psychiatric diagnoses, the ICD and DSM have only recently renewed attempts at harmonization. Previous nosological iterations demonstrate the oscillation in the importance placed on the biological focus, highlighting the tension between a gender- and culture-free nosology (solely biological) and a contextually relevant understanding of mental illness. In light of the release of the DSM 5, future nosological systems, such as the ICD 11, scheduled for release in 2017, and the Research Development Criteria (RDoC), can learn from history and apply critiques. This article aims to critically consider gender and culture in previous editions of the ICD and DSM to inform forthcoming classifications.

A fundamental debate in the philosophy of science is whether our central concepts are true or only useful instruments to help predict and manipulate the world. The first position is termed ‘realism’ and the second ‘instrumentalism’. Strong support for the instrumentalist position comes from the ‘pessimistic induction’ (PI) argument. Given that many key scientific concepts once considered true (e.g. humors, ether, epicycles, phlogiston) are now considered false, how, the argument goes, can we assert that our current concepts are true? The PI argument applies strongly to psychiatric diagnoses. Given our long history of abandoned diagnoses, arguments that we have finally ‘gotten it right’ and developed definitive psychiatric categories that correspond to observer-independent reality are difficult to defend. For our current diagnostic categories, we should settle for a less ambitious vision of truth. For this, the coherence theory, which postulates that something is true when it fits well with the other things we confidently know about the world, can serve us well. Using the coherence theory, a diagnosis is real to the extent that it is well integrated into our accumulating scientific data base. Furthermore, the coherence theory establishes a framework for us to evaluate our diagnostic categories and can provide a set of criteria, closely related to our concept of validators, for deciding when they are getting better. Finally, we need be much less skeptical about the truth status of the aggregate concept of psychiatric illness than we are regarding the specific categories in our current nosology.

This article describes the history of the Scientific Review Committee (SRC) for DSM-5 and reviews its background, procedures and deliberative processes, and conceptual/philosophical framework. The results of its work and the most important and contentious issues that arose in its efforts are reviewed. The central role of the SRC was to provide external review for all proposals for diagnostic change in DSM-5, evaluate them on their level of empirical support using objectively structured rules of evidence agreed upon in advance and make appropriate recommendations to the leadership of the American Psychiatric Association. While the creation of the SRC necessitated a great deal of additional work on the part of the SRC, the workgroups and the DSM-5 Task Force, the SRC succeeded in increasing the focus on empirical standards for nosologic change and providing a greater degree of consistency and objectivity in the DSM review process. The article concludes with recommendations, based on lessons learned, for similar efforts that might be included in future iterations of our psychiatric nosology.

This essay, which seeks to provide an historical framework for our efforts to develop a scientific psychiatric nosology, begins by reviewing the classificatory approaches that arose in the early history of biological taxonomy. Initial attempts at species definition used top-down approaches advocated by experts and based on a few essential features of the organism chosen a priori. This approach was subsequently rejected on both conceptual and practical grounds and replaced by bottom-up approaches making use of a much wider array of features. Multiple parallels exist between the beginnings of biological taxonomy and psychiatric nosology. Like biological taxonomy, psychiatric nosology largely began with ‘expert’ classifications, typically influenced by a few essential features, articulated by one or more great 19th-century diagnosticians. Like biology, psychiatry is struggling toward more soundly based bottom-up approaches using diverse illness characteristics. The underemphasized historically contingent nature of our current psychiatric classification is illustrated by recounting the history of how ‘Schneiderian’ symptoms of schizophrenia entered into DSM-III. Given these historical contingencies, it is vital that our psychiatric nosologic enterprise be cumulative. This can be best achieved through a process of epistemic iteration. If we can develop a stable consensus in our theoretical orientation toward psychiatric illness, we can apply this approach, which has one crucial virtue. Regardless of the starting point, if each iteration (or revision) improves the performance of the nosology, the eventual success of the nosologic process, to optimally reflect the complex reality of psychiatric illness, is assured.