I hadn’t spent more than a couple months in the world of psychiatry, before I realized that having more than one diagnosis was common. But a recent news item actually backs up this intuition with hard data:

A new study discovers a majority of psychiatry outpatients have more than one disorder, and more than one-third have at least three disorders. Researchers found major depression as the most common diagnosis followed by social phobia….

Most patients had more than one diagnosis; on average, patients had 1.9 current diagnoses. Patients with principal diagnoses of posttraumatic stress disorder (PTSD) and bipolar disorder had the highest number of diagnoses.

This is significant for a number of reasons, one of which the story points out:

Most treatment studies exclude patients with multiple disorders. The authors said, “We hope that by documenting the high frequency of comorbidity in clinical practice, this will provide the impetus for modifying how treatment studies are conducted to allow patients with multiple disorders to be included and to determine the outcome of comorbid disorders as well as the primary disorder that is being treated.”

What makes this consideration compelling is because clinical trials are often a way for patients with severe problems — which have not successfully been dealt with — to find additional treatment venues; but most these people who so need new treatments, are automatically disqualified, since they have more than one diagnosis.

Comorbidity is not really all that new; in fact, the current DSM-IV uses a multi-axial system, wherein personality disorders have been shunted into their own “slot” if you will (called Axis II). What this study shows is that there is a lot of comorbidity among what are Axis I disorders.

It’s nice to see my own intuition confirmed; it will be another thing entirely to see what psychiatry does with this information. Perhaps the current diagnosis system should be rethought, taking this tendency into account? They’re years away, yet, from releasing the DSM-V; perhaps it’s time to account for comorbidity in a more comprehensive way?