Descriptive Psychopathology: The Signs and Symptoms of ...

101 Chapter 4: Principles of descriptive psychopathology“bizarre” delusion (e.g. of control), or a hallucination of a continuous voice orvoices. But hallucinated voices and delusions identified as “bizarre” occur inother conditions, including mood disorder, and are not sufficient for a validdiagnosis of schizophrenia. For major depression, one of five features must be“depressed mood” or “anhedonia”, but anhedonia without other features of anabnormal mood is insufficient for the diagnosis of depressive illness.Attributing special weight to a feature would also undermine the simplicity of thelist system, requiring complicating subgroups or giving the feature the status of anindependent required criterion. Nevertheless, the presence of some features substantiallychanges the differential diagnosis. These are discussed throughout the text.Principles of diagnosisDiagnosis is difficult. If the checklist approach is applied and the patient fails tohave enough features, or has features not listed in the criteria, the “NOS” suffix isapplied. Understanding the principles of diagnosis can provide better diagnosticresolution. These principles begin with The Duck Principle, Sutton’s Law, andThe Rule of Parsimony. To be applied, the clinician must be able to recognizetypical syndromes, know the prevalence rates and other epidemiologic data ofdiseases, and know variations in disease presentation.The Duck Principle“If it looks, walks, and quacks like a duck, it’s a duck!” Appling the DuckPrinciple to diagnosis recognizes that many diseases are “typical” in their presentationmost of the time. If the patient’s pattern of features is quickly recognizableas representing disease A, the Duck Principle indicates that the patient will likelyhave disease A.Patient 4.12A 63-year-old woman greeted the psychiatry inpatient unit director at the frontdoor with a barrage of loud, rapid-fire demands. Despite his protestations thathe first had to check-in, she persisted, following him to the nurses’ station. Evenwith the door shut, she continued her comments through the glass.Later that morning, she stood for some time with her hands up against thewall opposite the nurses’ station as if holding it up. While doing this sheloudly, but in good humor, rapidly spoke to each passer-by.Recognized as the “Duck” of acute mania with catatonic features, lithiummonotherapy was prescribed, and the patient, who for years had been diagnosedas schizophrenic, remitted and for the first time did not require anantipsychotic agent.