Categories to Continuums: The Transdiagnostic Approach to Psychiatric Diagnosis

By: Lamisa Nubayaat, Biology and Society ‘2024

Sarah lived in fear of her own mind. She spent nights restlessly pacing around her room, mind racing with a million thoughts. A constant sense of worry consumed her, and she began to pull away from activities and people she once loved, weighed down by a deep sense of hopelessness. As days turned to weeks, the cycle persisted, pushing Sarah to seek help. Instead of receiving clarity, her diagnoses only made her more confused. Her symptoms were assessed separately, leading to a fragmented understanding of her overall mental state. Each professional told her something different, and overlooked the interconnected nature of her comorbid anxiety and depression. As she stared at the various scales asking her to rank and rate her symptoms, she couldn’t help but feel that they didn’t capture the depth of her suffering.

Sarah’s experience reflects the historical trend of making sense of psychological suffering through categorization, characterized by an attempt to distill complexities of the human psyche into neatly compartmentalized categories. From Hippocrates to Kraepelin, physicians have long theorized about fitting mental illnesses into distinct groupings [1]. Even the modern tool for diagnosis, the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5), is based on separating conditions into taxonomic categories based on symptoms [2]. As our knowledge expands, it's crucial to question the clinical utility of these traditional methods.

This popularized theory, known as the categorical approach, treats psychiatric conditions similarly to physical illnesses by using the presence of symptoms to determine if a person has a disorder. This understanding is concrete and posits that a disorder is present or absent with no in-between, implying two distinct states: normalcy and disorder [1, 3]. By providing a uniform and organized framework to discuss abnormal psychology, this model has become widely accepted and given medical legitimacy to the field. Despite the undeniable benefits, there is growing apprehension due to its inherent limitations. One major issue is its use of binary perspectives, categorizing symptoms as present or absent, disorder or no disorder, ultimately neglecting the nuanced ways symptoms may manifest. Furthermore, the considerable overlap between symptoms of different disorders poses challenges in accurate diagnosis and the identification of comorbidities [2]. 

Skepticism about this construct has resulted in increased endorsement for an alternative perspective: the transdiagnostic approach. This mechanistic framework emphasizes commonalities in underlying cognitive, emotional, and behavioral processes across various disorders, rather than focusing on individual conditions. Instead of viewing conditions as distinct entities, this method identifies dimensions, or shared processes that contribute to numerous disorders [4]. Notably, dimensions are normative, meaning they exist within all people at all times, ranging from normal to severely ill [1]. Examples include rumination, co-rumination, rejection sensitivity, negative urgency, perfectionism, etc [4]. This viewpoint is supported by evidence that mental disorders are better understood as existing along a continuum rather than in rigid categories [2]. 

This perspective offers a number of benefits, as it adeptly addresses many of the constraints of the traditional approach [2]. This approach revolutionizes psychiatric diagnosis by promoting a holistic, nuanced understanding. It is specifically useful in deciphering complex cases of co-occurring disorders, as it focuses on patterns rather than seeking to fit symptoms into discrete boxes [2, 5]. The framework is flexible, allowing for the recognition of evolving symptom trajectories and fluctuations over time, thus acknowledging the fluid nature of one’s mental state [2]. It is unique in that it is instrumental in identifying individuals experiencing distress that doesn’t align with traditional diagnostic criteria, allowing for a preemptive system of assessing the risk of developing a significant condition [3].

To treat underlying dimensions, a therapeutic framework, known as the Unified Protocol for Transdiagnostic Treatment of Emotional Disorders (UP), was developed in conjunction with this approach. Deviating from conventional disorder-specific methodologies, the UP is an emotion-centered, cognitive-behavioral intervention comprising five core modules that strategically focuses on temperamental traits and the emotion dysregulation underlying mental disorders [6]. Studies have found UP to be extremely successful in treating a wide range of disorders, showing improvements for both the primary diagnosis and comorbidities [6].

The public health implications of adopting this novel approach are profound. By offering a streamlined and cost-effective care plan, this approach will significantly reduce overall treatment length and cost for patients [7]. The clinical practicability and simplified training associated with interventions further enhance their accessibility in routine care settings and reduce training burden. By knowing just a singular protocol, mental health professionals can deliver evidence-based treatments for many disorders [4]. Most notably, the capacity to address multiple diagnoses within a single treatment is advantageous for individuals with comorbidities. Rather than prioritizing one disorder, this approach allows for the comprehensive treatment of all symptoms through a holistic therapeutic strategy [6]. 

While the transdiagnostic approach and the Unified Protocol mark strides in psychiatric care, their advancement brings forth inevitable challenges. The model prompts questions about whether a universal set of dimensions can effectively encapsulate the diversity of mental distress. There is uncertainty when deciding how many and how severe dimensions have to be to constitute a “disorder” and at what point on the continuum intervention is required [3]. Some suggest a hybrid approach, blending categorical and dimensional elements to harness the unique strengths of both [1]. As we navigate this dynamic landscape, scientists, mental health practitioners, and patients are tasked with evaluating the advantages and drawbacks. These debates are essential in deciding how to effectively integrate diverse perspectives and hopefully help patients like Sarah feel fully understood.

References

1. Avasthi, A., Sarkar, S., & Grover, S. (2014). Approaches to psychiatric nosology: A viewpoint. Indian Journal of Psychiatry, 56(3), 301. https://doi.org/10.4103/0019-5545.120560.

2. Dalgleish, T., Black, M., Johnston, D., & Bevan, A. (2020). Transdiagnostic Approaches to Mental Health Problems: Current Status and Future Directions. Journal of Consulting and Clinical Psychology, 88(3), 179–195. https://doi.org/10.1037/ccp0000482.

3. Suzuki, T. (2021, August 13). The Transdiagnostic Dimensional Approach: Another Way of Understanding Mental Illness. National Alliance on Mental Illness. https://www.nami.org/mental-health-systems/the-transdiagnostic-dimensional-approach-another-way-of-understanding-mental-illness. 

4. Sauer-Zavala, S., Gutner, C. A., Farchione, T. J., Boettcher, H. T., Bullis, J. R., & Barlow, D. H. (2017). Current Definitions of “Transdiagnostic” in Treatment Development: A Search for Consensus. Behavior Therapy, 48(1), 128–138. https://doi.org/10.1016/j.beth.2016.09.004. 

5. Bruno, A., Iannuzzo, F., & Muscatello, M. R. A. (2023). Comorbidity from a Categorical to a Transdiagnostic-Dimensional Approach: New Perspectives for Researchers and Clinicians. Clinical neuropsychiatry, 20(1), 7–8. https://doi.org/10.36131/cnfioritieditore20230101.

6. Barlow, D. H., Farchione, T. J., Bullis, J. R., Gallagher, M. W., Murray-Latin, H., Sauer-Zavala, S., Bentley, K. H., Thompson-Hollands, J., Conklin, L. R., Boswell, J. F., Ametaj, A., Carl, J. R., Boettcher, H. T., & Cassiello-Robbins, C. (2017). The Unified Protocol for Transdiagnostic Treatment of Emotional Disorders Compared With Diagnosis-Specific Protocols for Anxiety Disorders: A Randomized Clinical Trial. JAMA psychiatry, 74(9), 875–884. https://doi.org/10.1001/jamapsychiatry.2017.2164. 

7. Schaeuffele, C., Schulz, A., Knaevelsrud, C., Renneberg, B., & Boettcher, J. (2020). CBT at the Crossroads: The Rise of Transdiagnostic Treatments. International Journal of Cognitive Therapy, 14(14). https://doi.org/10.1007/s41811-020-00095-2.