Why is transdiagnostic psychiatry necessary?

Psychiatric diagnoses not only overlap in their clinical features, for instance in terms of sleep, appetite, interest, activity, cognition, mood, delusions, and self-harm, but many patients with a psychiatric diagnosis have psychiatric comorbidities,¹ said Professor Ole Andreasson, Oslo, Norway.

Any concept that is transdiagnostic must cut across diagnostic boundaries

In addition, common genetic variants are shared across mental traits and disorders, which suggests that the current diagnostic boundaries do not reflect distinct underlying pathogenic processes on a genetic level and that psychiatric disorders are interconnected.²

The transdiagnostic approach has, therefore, been developed to cut across the existing diagnostic boundaries of current psychiatric classification systems to provide a better classification system for psychiatric disorders and guide more effective prevention and treatment.

Overall, the quality of transdiagnostic studies so far has been poor

What has been achieved so far using the transdiagnostic approach?

Professor Marco Solmi, Ottawa, Canada, presented the results of a systematic review of transdiagnostic psychiatric research (based on the word transdiagnostic in the title) he carried out with colleagues to analyze the quality and findings of transdiagnostic studies.³

The study revealed that most of the 111 transdiagnostic studies analyzed had focused on depressive and anxiety disorders, and that 20% of the studies analyzed were not actually transdiagnostic. Overall, the quality of the studies was low.

TRANSDiagnostic research recommendations have been developed to improve future transdiagnostic psychiatric research

To guide and improve future transdiagnostic psychiatric research on prevention, treatment and diagnostic and clinical characterization, Professor Solmi and his colleagues therefore propose practical TRANSDiagnostic research recommendations as follows:³

• Transparent definition of the existing gold standard diagnosis
• Report the study design and primary outcome, and define the transdiagnostic construct in the abstract and main text
• Appraise the conceptual framework of the transdiagnostic approach, for instance across diagnoses or beyond diagnoses
• Numerate the diagnostic categories in which the transdiagnostic construct is being tested and then validated
• Show through comparative analyses the degree of improvement of the transdiagnostic approach against the specific diagnostic approach
• Demonstrate the generalizability of the transdiagnostic approach through external validation studies

Transdiagnostic research should not neglect individual diagnoses

Use of the transdiagnostic approach for prevention

Professor Solmi presented a meta-umbrella systematic synthesis of umbrella reviews (systematic reviews of meta-analyses of individual studies) he had carried out on non-genetic risk or protective factors for any diagnosed mental disorders. The TRANSD criteria were applied to test the transdiagnosticity of factors.⁴

Many transdiagnostic risk factors occur during childhood, the perinatal period or gestation⁴

The study revealed many transdiagnostic risk factors for mental disorders, many of which occur during childhood, the perinatal period or gestation.⁴

Universal prevention might be more likely to be evaluated using transdiagnostic approaches in the future, but the cost-effectiveness of transdiagnostic approaches should be evaluated before discontinuing effective diagnostic categories-based paradigms, concluded Professor Solmi.