Mental health disorders are typically assessed using a broadly defined classification, through diagnostic manuals such as the DSM or ICD. However, this approach has recently been criticised due to its repetitional nature, low descriptive power of patient heterogeneity, and inability to map on to the underlying cognitive mechanisms. In this post I briefly discuss the historical origins of the diagnostic manual, summarise recent alternative frameworks.

A (very) brief history of psychiatry

In antiquity, one of the key philosophical questions pertained to how the human body functioned. There were two main schools of thought. The first was the ‘Cardiocentric view’ popularised by Aristotle and endorsed by other prominent Greek thinkers including Diocles and Praxagoras. This view was substantiated by Aristotle on a number of points including ‘the lack of sense organs’ within the brain, as well as it’s plain visual appearance and inability of feeling (Frampton, 1991). The second view was the ‘Cephalocentric view’ which posited the brain was instead the primary source of human behaviour and emotion. Interestingly this correct interpretation predates the cardiocentric view, with Alcmaeon of Croton in the 5th century B.C. being the initial proponent. It is for this reason that he is often called the ‘Father of Neuroscience’. By extension, he may also be dubbed the ‘Father of Psychiatry’ in that he also was the first to distinguish a neurological condition as having a non-divine cause. He did so with reference to epilepsy (Debernardi et al., 2010), a view which would influence other prominent Greek physicans including Hippocrates.

Moving to the 18th century, a different figurehead, Benjamin Rush (‘The Father of American Psychiatry’) was an initial supporter of patient-centric treatment of mental health conditions (Farr, 1944). The period encompassing the 17th and 18th centuries often represents a negative viewpoint of mental health, with patients committed to insane asylums, chained to their beds and not quizzed regarding their condition. Rush instead sought to engage with patients, as this would give a more detailed overview of their condition. Wilhelm Griseinger then built upon this further by introducing the concept of a ‘pathophysiology’ where mental disorders were the product of physiological changes in the body and brain. He also suggested that symptoms at different time points may in fact be caused by time-varying effects of the same condition (Marx, 1972). And finally, it was Emil Kraepelin who was the first to practically develop and introduce the concept of ‘diagnostic classification’ (at least in the conventional categorical sense). This stems from his work with psychosis, to which his opinion differed from popular opinion at the time. Namely, Kraepelin did not believe that certain symptoms were characteristic for specific illnesses, rather that that specific combinations of symptoms and the time-course could be used to identify them instead (Ebert & Bar, 2010).

The development of modern classification systems

It is important to understand the historical origins of psychiatry because they have directly influenced the modern systems that we use. For example, the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) is the primary diagnostic manual used in the diagnosis of mental disorders in North America. It is developed in an iterative process from earlier versions, which they themselves are influenced by earlier-still diagnostic manuals. For example, the Schneideran First Rank symptoms for schizophrenia developed by Kurt Schnieder in 1950, subsequently influenced Spitzer’s initial classification in the DSM-III three decades later (Kendler, 2009).

There are additional limitations based in history. The developers of such classification systems were in a relative state of ignorance regarding the (as we now understand) incredibly complex etiology of mental health disorders. This was reflected in the ‘essentialist view’ a now-challenged framework, viewing mental health disorders are being caused by some shared essential criterion (Kendler, 2010; Adriens and De Block, 2013). In addition, there is the tendency to project a priori beliefs about the things they are classifying, and the nature and goals of those classifications (Kendler, 2009).

Current treatments for mental health disorders demonstrate a success rate far behind what is necessary to keep up with the concurrent increase in prevalence. This lack of efficacy is partly a consequence of the current methods used to classify, diagnose and treat mental health disorders, primarily diagnostic manuals such as the DSM and ICD, which have been the subject of scrutiny in recent years due to its repetitional nature (Forbes et al., 2023), low descriptive power of patient heterogeneity, and inability to map on to the underlying cognitive mechanisms. Subsequently, there are a number of alternative approaches, more strongly rooted in modern definitions of symptomatology. These include the Research Domain Criteria (RDoC, Insel et al., 2010), the Network Theory of Mental Disorders (Borsboom, 2017) and the Hierarchical Taxonomy of Psychopathology (Kotov, 2017). Each of these, whilst slightly different in their approach, aim to incorporate multiple ‘layers’ of influence when considering the etiology and development on mental health conditions, and appreciates their transdiagnostic nature.

The RDoC for example uses a core of five domains each capturing a distinct range of cognitive and behavioural processes, including: Negative Valence Systems (fear, anxiety, frustration), Positive Valence Systems (motivation, reward, pleasure), Cognitive Systems (Attention, perception, learning), Social Processes (Communication, interpersonal interactions, attachment) and Arousal and Regulatory Systems (Sleep, wakefulness, stress response).

Within each of these domains, specific dimensions, called constructs, capture key aspects of functioning. For example, “reward anticipation” is a construct within the Positive Valence Systems domain. These constructs are importantly assessed through various units of analysis at different levels, such as neuroimaging (systems), cognitive tests (behavioural), or self-report surveys (social).

Somewhat similarly, The HiTOP framework, aims to re-classify mental health classification by introducing a hierarchical organization of symptoms and behaviours. It does this by organizing symptoms into increasingly broader “spectra”. It also focuses on the idea of a continuous rather than discrete framework of classification. Instead of discrete categories like “bipolar disorder,” HiTOP uses continuous dimensions like “internalizing distress” or “externalizing disinhibition” to describe an individual’s profile. This is reflected in its transdiagnostic approach, where it recognizes that symptoms often overlap across traditional diagnoses. This reflects how similar symptoms can have different underlying causes in different people, blurring the lines between categories. Finally, also similar to RDoC, HiTOP considers evidence from various levels, including genes, brain circuits, behaviors, and subjective experiences, to create a comprehensive picture of mental health.

The network theory is different from the HiTOP and RDoC, in that it also proposes a statistical framework. It does this by virtue of proposing that mental disorders are best represented by complex webs of interacting symptoms, which constitute individual nodes in a network. Subsequently, various nodes and networks influence each other more or less based upon their properties as dictated by graph theory, such as distance and complexity. Consequently, complex networks encompassing both symptomatic and social influences can describe how certain symptoms and factors affect one another.

Conclusion

Mental health has always been a difficult concept to classify, due to the underlying complexity and heterogeneity across individuals. In addition, unlike conventional diseases which you can see, and perform a range of viable biological tests, mental disorders are not so easily tested, nor is there an universal objective measure in assessment. Understanding the historical origins of diagnostic classification is an important topic for neuroscientists interested in psychiatry to consider, as whilst we may be relatively educated to test scientific theories, we should also understand the nature of what we are ultimately looking to treat. Whilst the ICD and DSM are still the primary method of diagnosis, stemming from its practicality, from a scientific perspective, taking a complex approach is becoming more and more influential. Only by understanding mental health in all its complexity, can we subsequently develop effective treatments.

References

Adriaens, P. R., & De Block, A. (2013). Why we essentialize mental disorders. Journal of Medicine and Philosophy, 38(2), 107-127.

Borsboom, D. (2017). A network theory of mental disorders. World psychiatry, 16(1), 5-13.

Debernardi, A., Sala, E., D’Aliberti, G., Talamonti, G., Franchini, A. F., & Collice, M. (2010). Alcmaeon of croton. Neurosurgery, 66(2), 247-252.

Ebert, A., & BĂ€r, K. J. (2010). Emil Kraepelin: A pioneer of scientific understanding of psychiatry and psychopharmacology. Indian journal of psychiatry, 52(2), 191-192.

Farr, C. B. (1944). Benjamin Rush and American psychiatry. American Journal of Psychiatry, 100(6), 2-2.

Forbes, M. K., Neo, B., Nezami, O. M., Fried, E. I., Faure, K., Michelsen, B., 
 & Dras, M. (2023). Elemental psychopathology: Distilling constituent symptoms and patterns of repetition in the diagnostic criteria of the DSM-5.

Frampton, M. F. (1991). Aristotle’s cardiocentric model of animal locomotion. Journal of the History of Biology, 291-330.

Insel, T., Cuthbert, B., Garvey, M., Heinssen, R., Pine, D. S., Quinn, K., 
 & Wang, P. (2010). Research domain criteria (RDoC): toward a new classification framework for research on mental disorders. American Journal of psychiatry, 167(7), 748-751.

Kendler, K. S. (2009). An historical framework for psychiatric nosology. Psychological medicine, 39(12), 1935-1941.

Kendler, K. S., Zachar, P., & Craver, C. (2011). What kinds of things are psychiatric disorders?. Psychological medicine, 41(6), 1143-1150.

Kotov, R., Krueger, R. F., Watson, D., Achenbach, T. M., Althoff, R. R., Bagby, R. M., 
 & Zimmerman, M. (2017). The Hierarchical Taxonomy of Psychopathology (HiTOP): A dimensional alternative to traditional nosologies. Journal of abnormal psychology, 126(4), 454.

Marx, O. M. (1972). Wilhelm Griesinger and the history of psychiatry: a reassessment. Bulletin of the History of Medicine, 46(6), 519-544.