Pathognomonic Symptoms: Why Multiple Personality is a More Definite Condition than Schizophrenia or Bipolar Disorder

In my December 8, 2014 post, I pointed out that of three psychiatric diagnoses—schizophrenia, bipolar disorder, and multiple personality—multiple personality is the most definite and specific condition, and is, in that regard, the least controversial.

There is no symptom of schizophrenia that is found only in schizophrenia. There is no symptom of bipolar disorder that is found only in bipolar disorder. But there are symptoms of multiple personality that are found only in multiple personality.

In other words, of the three conditions, multiple personality is the only one with any symptoms that are “pathognomonic,” defined as follows:

“Pathognomonic (often misspelled as pathognomic and sometimes as pathomnemonic) is a term, often used in medicine, that means characteristic for a particular disease. A pathognomonic sign is a particular sign whose presence means that a particular disease is present beyond any doubt. Labelling a sign or symptom "pathognomonic" represents a marked intensification of a "diagnostic" sign or symptom.

“While some findings may be classic, typical or highly suggestive in a certain condition, they may not occur uniquely in this condition and therefore may not directly imply a specific diagnosis. A pathognomonic sign or symptom has very high specificity but does not need to have high sensitivity: for example it can sometimes be absent in a certain disease, since the term only implies that, when it is present, the doctor instantly knows the patient's illness. The presence of a pathognomonic finding allows immediate diagnosis, since there are no other conditions in the differential diagnosis.” —Wikipedia

So if someone says that multiple personality is the most controversial psychiatric diagnosis, ask them, “Compared to what?” And if they say schizophrenia, bipolar disorder, or most other psychiatric diagnoses, ask them, “Does it have any symptoms that are pathognomonic?" Multiple personality does.