Descriptive Psychopathology: The Signs and Symptoms of ...

102 Section 2: The neuropsychiatric evaluationSutton’s Law“Go where the money is.” Sutton’s Law is applied when the Duck Principle cannotquickly lead to the diagnosis. It derives from an interview with the famous NorthAmerican bank robber of the 1950s, Willie Sutton, who when asked why herobbed banks, responded incredulously, “Because that’s where the money is.”Sutton’s Law applied to diagnosis instructs that under most circumstances, thepatient will have a common rather than a rare disease. The Zebra Principle is acorollary of Sutton’s Law. It states that outside of sub-Saharan Africa, if you hearhoof beats it will likely be horses, not zebras. Again, common diseases are morelikely than rare ones. Among patients 60–70 years of age who develop cognitiveimpairment over several months, depression is four times more likely to bethe cause than Alzheimer’s disease. 22 Patient 4.13 illustrates a tragic violation ofboth The Duck Principle and Sutton’s Law.Patient 4.13 23A 42-year-old woman became depressed. She was unable to sleep, became withdrawn,and refused to eat. She initially improved with tricyclic antidepressanttreatment, but two weeks into therapy she became “confused”, wandered aimlesslyaround her house, and fully withdrew from family and friends. CT-scanrevealed cortical atrophy. A neurologist diagnosed Alzheimer’s disease andrecommended long-term care as he concluded that her condition was “hopeless”.Rather than confining her to a nursing home, her family cared for her athome for the next seven years. During that period she was mostly mute,stared, rarely moved, postured, and was incontinent of urine and feces. Aftermany years, the illness was finally recognized as a mood disorder withcatatonia and stupor. ECT resolved both and she resumed her role as ahomemaker. But seven years of her life were “lost”.Severe depression can be confused with dementia from degenerative brain diseaseand when a depressed patient’s cognitive functioning is markedly impaired, theterm “pseudodementia” is applied. 24 Patient 4.13’s initial depressive features andlater catatonia, however, is a classic “duck” signifying a mood disorder. Even ifmissed, however, applying Sutton’s Law will lead to the same diagnostic conclusion.Depression is many times more common than Alzheimer’s disease in personsunder 60 years of age. The most common cause of catatonia is mood disorder. 25The Rule of Parsimony“The simplest explanation is usually the best explanation.” The Rule of Parsimonytries to bring order to clinical chaos. When the patient exhibits several syndromessimultaneously, the rule encourages the clinician to search for a common process