Dr. B's Blog

4 vs. 5. What's the difference?

[Part one of this series of blog posts (because it has to be a series or I'm never going to get any of is published) will be a quick orientation to the concept of psychiatric diagnosis. Future parts will be much more extensive and go into the ongoing discussion regarding categories vs. dimensions in the DSM-5.] If you answered “1” to the question posed in the title of this article, you’d be right and wrong depending on what the units were measuring. When it comes to mental health diagnoses, it’s all in what is being measured. It could be a difference this >< large or one quite a bit bigger.

The debate about the "correct" way to make a diagnosis is at least as old as the Diagnostic and Statistical Manual and its categorical definition of mental illness. A quick lit search for the terms "categorical" "dimensional" and "diagnosis" reveals a discussion going back over 25 years.(1, 2, 3, 4 ).

Why the ongoing debate? The question essentially boils down to whether psychopathology is different in kind or merely in degree from typical emotional experience. That is, do people who experience what is considered a diagnosable mental illness have a qualitatively different experience of emotion than others?

Is sadness in Major Depressive Disorder a different kind of sadness? Or is it just a difference in how intense it is?

Is the anxiety someone with Generalized Anxiety Disorder experiences a different kind of anxiety? Or is it just more intense or pervasive?

How does a psychologist make a diagnosis?

The "right" way to make a diagnosis is to ascertain the level of severity of one's symptoms through either a structured or unstructured interview or questionnaire or other form of assessment. Using the information gleaned from this assessment, symptoms are compared to what's listed in the DSM to see if enough symptoms have been endorsed to be given a particular diagnosis. A thorough psychologist/assessor would make sure that there are no rule-outs or disorders that supercede the one being considered. 5

The decision after an assessment is a binary one: does the person meet enough criteria to be given this diagnosis? Take the diagnosis of Major Depressive Disorder. There are 9 criteria that can be considered. Five of those nine criteria must be met, with one of them being the first criteria. If a person meets 5, they can be given the diagnosis. If a person meets 4 of them, they cannot. That person would be considered to have "subthreshold" depression.

What's the difference between those two people? It could be just a matter of 1 fewer day of sadness or it could be a lack of something more substantive like hopelessness. The former is much less of an actual difference than the latter, obviously, and can make a significant difference in presentation and outlook.

(More to come on this topic in a future post, probably next week.)

  1. A recent article in Wired Magazine talks about this debate.
  2. Some more discussion of the Wired article can be found on mindhack. These articles are just a couple of the many on the subject.
  3. Thomas Widiger’s classic article on Axis II and categories back in 1993.↩
  4. Lorna Smith Benjamin’s response to Widiger.
  5. For example, if a person has ever had a manic episode, future diagnoses of Major Depressive Disorder are ruled-out because Bipolar Disorder would supercede the diagnosis due to the history of a manic episode.