Longitudinal Development of Symptoms and Staging in Psychiatry and Clinical Psychology: A Tribute to Giovanni Fava.

The introduction of diagnostic manuals, such as the first mention of mental disorders in the International Classification of Diseases (ICD-6) in 1948 [1] and the Diagnostic and Statistical Manual of Mental Disorders in 1952 [2], was a big step forward in the fields of psychiatry and clinical psychology. The operationalization of diagnostic criteria for mental disorders such as depression or schizophrenia, which lacked characteristic morphological features or laboratory biomarkers, greatly increased the reliability of clinicians’ diagnoses and their capacity to communicate with one another. However, those classifications were based on a cross-sectional view and informed clinicians, researchers, patients, and their relatives only little about the expected longitudinal course and development of a mental disorder. More specifically, cross-sectional diagnostics did not inform about trajectories of symptom severity over time, individual characteristics and combinations of symptoms, or comorbidities. Such elements are important when it comes to developing a sequential treatment plan and adjusting it as illness characteristics and symptom levels change over time. As early as 1967, Feinstein encouraged clinicians to develop their own “basic science” to use clinical phenomena and data to generate classification systems and to ultimately analyze the clinical process quantitatively [3]. Feinstein appears to have been a lone voice calling in the wilderness at that time though.