This is the third in our discussion of psychiatry’s diagnostic bible, the DSM. In May this year, an updated edition - the DSM-5 - will replace the current DSM-IV, which has been the last word since 1994. How influential is the DSM? In response to last week’s piece, Psychiatric Incompetence and the DSM, Tabby, who works in a clinic, reports that the manual is regularly consulted by the therapists and psychiatrist who work there. When they can’t seem to put a finger on the condition, she reports, she finds them “pouring through ‘the book,’ or huddle, two or three of them, in a circle discussing and arguing what each other thinks it is.”

There is one catch: Using the DSM to arrive at a precise diagnosis is like relying on Apple Maps to arrive at your destination. As I pointed out in my previous post, the DSM-IV has no way, practical or impractical, of differentiating bipolar depression from unipolar depression. Why it is critical to do so is that an antidepressant, which may work just fine for treating unipolar depression, may possibly be the worst drug a doctor can prescribe to someone in the bipolar spectrum (where the risk of the pill inducing a switch into mania or in speeding up the cycle is very high).

Another way of phrasing this: If an antidepressant worked the same for both bipolar depression and unipolar depression, diagnostic mistakes would not have the major consequences they do now.

So, imagine Tabby’s clinicians huddling over their office copy of the DSM-IV. Under “Major Depressive Disorder,” they are referred to “Major Depressive Episode,” where they mull over the nine-symptom checklist. First, one of two symptoms must be checked off: “Feeling depressed” (which we can loosely interpret as feeling sad) or “Loss of pleasure” (which is another way of saying you don’t necessarily have to feel sad to have depression). Then we have an additional seven symptoms to choose from. In all, at least five of nine symptoms need to be checked off.

Fine, Jim Dandy. But what if one of the clinicians suspects bipolar? The catch is the patient is presenting as depressed, with no sign of mania. Indeed, the patient in her depressive state might not even recall feeling good at any time in her life. I am guessing that Tabby’s clinicians know better than to look up what bipolar depression involves. This is because DSM-IV bipolar depression is an exact cut and paste of unipolar depression.

But are the two the same? Let’s think this through: The same antidepressant that may be beneficial for one condition may do a serious number on your brain for the other. Clearly, there is a different biological basis to the two depressions. On my website, mcmanweb, I quote Alan Swann of the University of Texas, Houston in support:

The differing biological properties of unipolar and bipolar depression suggest that treatments that were originally intended for unipolar depression may not be optimal for bipolar depression.