When you get a referral, you are presented with a great deal of information, and it isn’t clear which information will be relevant to your eventual understanding of the patient’s health problems. Some of the material that is contained in the referral will be explicit, some implied, details may be inaccurate, and surely, much will be left out.
Now consider that once you greet a patient in the waiting room, you will have even more information. You will notice how the patient is dressed and what he’s been doing while waiting; you will observe his facial expression, level of social comfort, his gestures and gait. And, before you even hear the patient’s voice or ask a single question, all of these experiences will affect you and have an influence on how you are inclined to think about the diagnosis.
Diagnostic problem solving is extremely engaging for physicians, but it is not the defined type of problem solving one encounters with something like a crossword or Sudoku puzzle in which there are 26 letters or 9 numbers that are manipulated to form one unique solution. Making a diagnosis is complex problem solving in an uncertain domain. Any particular information or observation might be relevant; and any particular information or observation might be irrelevant (noise). The patient might leave out crucial parts of the illness story, perhaps not realizing that they are important. Or the physician–problem-solver may have insufficient knowledge, perhaps never having heard of the diagnosis that actually explains the patient’s symptoms. There also could be more than one diagnosis; and these diagnoses might be interacting with one another.
System 1 and/or system 2 cognition
The reigning theory about diagnostic problem solving is that it involves two interacting cognitive systems—system 1 and system 2.3
System 1 cognition is illustrated by the experience of seeing a patient for the first time and “knowing” immediately that the patient has, for example, schizophrenia. System 1 is based on mental pattern-recognition; it is intuitive, but honed and refined by experience; it is fast, effortless, and operates outside of awareness. While this system is extraordinarily efficient, processing large amounts of information very rapidly, it is also highly error-prone and open to biases (predispositions to think and act a certain way) of which the clinician is generally not aware.
System 2 cognition is exemplified by the generation of a differential diagnosis list and examining the evidence for and against each diagnosis. System 2 utilizes explicit rules of logic; it is slow, effortful, entirely conscious, and analytical. Clinicians naturally favor the use of system 1 cognition because it is effortless. But the most effective clinical reasoning involves going back and forth iteratively between system 1 and system 2 cognition.
Dr Schildkrout is Assistant Professor of Psychiatry, part time, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA. She is the author of two books: Unmasking Psychological Symptoms: How Therapists Can Learn to Recognize the Psychological Presentation of Medical Disorders and Masquerading Symptoms: Uncovering Physical Illnesses That Present as Psychological Problems.
1. Ball J, Balogh E, Miller BT, Eds. Improving Diagnosis in Health Care. Washington, DC: National Academies Press; 2015.
2. Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med. 2003;78:75-780.
3. Croskerry P. Clinical cognition and diagnostic error: applications of a dual process model of reasoning. Adv Health Sci Ed. 2009;14:27-35.
4. Yates BL, Koran LM. Epidemiology and recognition of neuropsychiatric disorders in mental health settings. Ovsiew F, Ed. Neuropsychiatry and Mental Health Services. Washington, DC: American Psychiatric Press; 1999: 23-67.
5. Koranyi EK. Morbidity and rate of undiagnosed physical illness in a psychiatric clinic population. Arch Gen Psychiatry. 1979;36:414.
6. Schildkrout B. Complexities of the diagnostic process. J Nervous Mental Dis. 2018;206:488-490.
7. Schildkrout B. Masquerading Symptoms: Uncovering Physical Illnesses That Present as Psychological Problems. New York: John Wiley & Sons; 2014.