Introduction: The “Lumpers” and the “Splitters”


In this Special Report we offer articles that address the interplay of psychiatric and infectious disease.

interplay of psychiatric and infectious disease



During my fellowship training, an esteemed mentor distilled the chief philosophical difference between those of us in the specialty of psychiatry and our cousins in the specialty of neurology as the dichotomy of “lumpers” and “splitters.” He clarified that we psychiatrists see a group of symptoms (like hallucinations, delusions, social withdrawal) and lump them into a diagnosis (ie, schizophrenia). Neurologists, on the other hand, tend to take a group of patients with similar symptoms and divide them among a multitude of diagnoses based on the order that the symptoms presented, the most predominant symptom, or other such criteria.

From a theoretical standpoint, he offered no judgment as to which was the most appropriate of these approaches. Pragmatically, though, he did underscore that the problem we face on the lumping side is that our bailiwick is constantly being whittled down by our splitting counterparts. There is no clearer illustration of this issue than the interplay between mental illness and infectious disease.

The history of psychiatry is littered with examples of groups of patients considered mentally ill who were later found to have an infectious cause of their symptoms. Perhaps the chief landmark of this type of diagnostic transition is now well over a century old as the term general paralysis of the insane gave way to the diagnosis of neurosyphilis.

We have seen groups of patients cross the theoretical bridge from what many of us were taught to call primary mental illness to organic brain disease as the tools available to medicine allowed us to split off a specific causative mechanism for their symptoms. Some benefited from treatment directed at their pathogen, others endured the provision of an explanation without hope of improvement. Many found themselves outside the reach of psychiatric care regardless of whether their symptoms had changed.

We are now in an era where the acceleration of our ability to identify in vivo pathology of the central nervous system has birthed entire new diagnostic entities (see the burgeoning number of antibody-specific subtypes of autoimmune encephalitis). To avoid psychiatry being left as “the specialty of emotional or behavioral symptoms that we do not have an explanation for (yet),” it behooves us to expand our diagnostic repertoire beyond the lumping constructs of symptom groupings.

To that end, in this Special Report we offer articles that address the interplay of psychiatric and infectious disease. The articles address the potential infectious causes of neuropsychiatric symptoms, the potential neuropsychiatric adverse effects of drugs used in the treatment of infectious diseases, and the role of psychiatry in the management of pandemics. All include information vital to maintaining our ability to provide timely diagnoses and effective treatment to the patients we serve.


Dr Caplan is Chair of Psychiatry, St Joseph’s Hospital and Medical Center, Phoenix, AZ. He reports no conflicts fo interest concerning the subject matter of this Special Report.

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