In my previous post on American psychiatry’s new and fifth edition of its “diagnostic manual” for mental conditions, I covered the history of the previous four editions of the “DSM” which stands for Diagnostic and Statistical Manual.
I will talk of two topics in this post; first as understandable explanation of the ‘sorting science’ that lies behind how psychiatric diagnostic categories are arrived at, and, second some of the misses and one correct addition in DSM-5.
The statistical science behind the DSM from its 3rd edition onward, is called “factor symptoms cluster analysis.” Quite a mouthful but simple concept once it is parsed and enumerated, element by element.
1. symptoms: these are the cardinal signs of an illness e.g., rash bumps and fever of chicken pox for instance. For sake of explanation I will grossly simplify all this and not get into such controversies as only a few symptoms in the world of medicine are truly unique and totally specific to an illness, which is called “pathogonomonic.”
2. all the symptoms that are clinically observed to appear in someone with the illness being considered are grouped together (clustered);
3. many cases and aggregated together, the more the better as in statistical sampling, it is a basic precept that the larger the sample size, i.e., the more people that are surveyed in a public opinion poll, the more accurate the groupings will be;
4. many clinicians, psychiatrists, are involved in pooling all these cases together as no one psychiatrist could have thousands of cases active of the same kind of symptom bearing patient illness;
5. a sorting process takes place in which it is determined, often in the early days before true computerized high speed sorting, counting and grouping could be performed, by manually grouping together cases that shared the same symptoms sets;
6. a name was discussed and commonly agreed to; its more specific subtypes were worked out with the addition of ‘qualifier’ description terms such as acute, subacute or chronic to give a simplest example (but one no longer used nowadays…);
7. confirmatory field trials were the performed utlizing the resulting description diagnostic criteria sets so generated and the members of the large working DSM edition task force would meet periodically, present cases they had found within their own worlds of practice and case by case debates would ensue whether the offered case “fit.”