Article summary of A review of approaches and models in psychopathology conceptualization research by Eaton a.o. - 2023

What is nosology?

Nosology is the classification of (mental) diseases. Mental disorder classifications provide frameworks that underlie applied clinical treatments and scientific research in order to understand, assess, predict, prevent, and treat psychopathology. There are different classification frameworks, each with their own unique position on how mental disorders should be diagnosed, classified, and assessed.

What are negative aspects of ¨official¨ classification systems, such as the DSM-5?

Classification systems such as the DSM-5 are composed almost exclusively of large sets of dichotomous diagnoses which are themselves composed of a set of diagnostic criteria. They define disorders as independent of one another. The limitations of these nosologies are:

• High comorbidity rates of distinct mental disorders that cannot be explained.
• Symptom overlap obscures distinctions between categorical diagnoses. Two people with the same diagnosis may only have one symptom in common.
• Symptoms are of a dynamic nature and a checklist-approach (present/absent) does not account for this.
• They hinder progress in identifying biomarkers of mental illness and improving treatment outcomes.

What are polythetic criterion sets?

Polythetic criterion sets mean that if a person exhibits a pre-defined number of criteria and experiences related distress or impairment, that that person is assigned a certain diagnosis.

What are three leading alternative approaches in psychopathology classification?

There are attempts to overcome above mentioned limitations. Three leading alternative approaches are: 

• Transdiagnostic dimensional approaches
• Network psychometric approaches
• Clinical staging approaches

What are transdiagnostic dimensional approaches?

Transdiagnostic dimensional approaches use continuous dimensions which represent unbroken spectra that range from very low to very high levels. These dimensions reflect core building blocks of variation that characterize multiple disorders. In this way, one transdiagnostic dimension (for example internalizing) can include psychiatric phenomena from different diagnoses of the same type as well as from different groupings of disorders.

What are the pros of transdiagnostic dimensional approaches compared to official nosologies?

Three pros of transdiagnostic dimensional approaches compared to official nosologies are:

• The dimensionality offers a more realistic picture of the world. Individuals show very different levels of psychopathology that range widely and have no clear points of discontinuity across severity levels.
• They embrace comorbidity by modeling the relationships among mental health variables. 
• Dimensionality overcomes the need for largely arbitrary diagnostic criterion thresholds (e.g. with 5 criteria you are diagnosed, but with 4 criteria you are not). Such thresholds obscure important similarities and differences, and transdiagnostic dimensions don´t have thresholds. The (dis)similarity between two individuals is characterized by their levels on the underlying dimensions.

How did transdiagnostic dimensional approaches arise?

To overcome problems with official personality disorder diagnoses, personality disorder researchers moved toward dimensional models. They then began applying similar methodologies to broader types and numbers of disorders. They were able to build upon existing research and outperformed models from official nosologies with regard to superior model fit to observed data and structural validity.

What is the Five-Factor Model (FFM)?

The FFM is a set of five broad trait dimensions that was developed to represent as much of the variability in individuals´ personalities as possible, using only a small set of trait dimensions. The five dimensions are extraversion, agreeableness, conscientiousness, neuroticism, and openness. 

What is the Hierarchical Taxonomy of Psychopathology (HiTOP)?

The HiTOP is a framework that organizes dimensions based on empirical patterns of covariation into a hierarchy. It has six core spectra at its center: internalizing, detachment, thought disorder, antagonistic externalizing, disinhibited externalizing and somatoform. Individual symptoms cohere into higher-level syndromes, then broader subfactors, then the spectra and ultimately super-spectra. 

What are network psychometric approaches?

Network psychometric approaches view mental health as a complex, dynamic biopsychosocial system. Psychopathology symptoms influence each other and mental disorders emerge from the relations among these symptoms. Mental disorders are conceptualized as within-person systems that unfold over time and have distinct healthy and disordered states. Transitions between states may be abrupt or gradual. This is what distinguishes network psychometric approaches from dimensional models.

What are the three notable key findings from network approaches?

Three notable key findings from network approaches are:

• The idea of mental disorder as a dynamical system has inspired other scientific disciplines, like meteorology and ecology. They have applied the same idea to their fields and developed statistical tools for forecasting system transitions to different states. Variable-specific and system-level early warning signals might forecast transitions from healthy to disordered states.
• Bridging the gap between theoretical and statistical models via formal theories. Formal theories sidestep ambiguities of language by requiring mathematical notation and allow researchers to generate data to investigate what theory-implied data would look like. The generated data can then be compared to observed data, leading to theory building and testing.
• Tools of social network analysis have been used to investigate the predictive utility of network approaches.

What are some of the negatives of network approaches?

Some negatives of network approaches are:

• Cross-sectional networks do not lend themselves to causal inference.
• Network theories often presuppose feedback loops, abrupt phase transitions, systems with multiple states, and asymmetric relations among nodes. Some of these phenomena can only come out of non-linear relationships. Therefore it is still a question how to best interpret the model output.
• Network graphs are easily over-interpreted because they usually don´t provide information about the accuracy of parameter estimates.
• It is not clear which model features are suited to assess replicability, therefore there are questions about the empirical replicability of network models.

What are clinical staging approaches?

Clinical staging approaches identify where someone is along a continuum of illness which is divided into stages. They facilitate the selection of preventive or pre-emptive treatment and the prediction of prognosis. In psychiatry they identify six stages:

• Stage 0: At-risk
• Stage 1a: Help-seeking with distress
• Stage 1b: Attenuated syndromes
• Stage 2: Full-threshold disorder
• Stage 3: Recurrence or persistence
• Stage 4: Treatment resistance

These stages can be applied to any disorder that tends to or might progress. The transition between the stages corresponds to an increase in severity, symptom specificity and functional impairment.

What is the importance of studying within-person psychopathology for psychopathology conceptualization?

Studying within-person changes can provide insights about how symptoms cluster over time, how comorbidity develops, and inform diagnostic and psychotherapeutic processes. Within-person studies can show how individuals differ from their own average instead of the between-person average. Changes in within-person symptom dynamics can help to discover why individuals at risk for psychopathology transition into pathological states.