People who study the classification of psychiatric disorders are often grouped into lumpers and splitters. The lumpers tend to see just a few broad categories of mental illness while the splitters try to subdivide psychopathology into smaller and more specific entities. Both sides have some research evidence to support their view. The fact that the number of official psychiatric disorders has risen to about 300 suggests that the splitters have had the advantage. At the same time, trying to find just about anything (genes, brain regions, causes, treatments, etc.) that are specific to just one disorder or even type of disorder has proven to be extremely challenging, becoming easy fodder for the folks who still deny that many disorders even exist.
A new study, however, scores big for the lumpers. Using data from the well-known Dunedin Multidisciplinary Health and Development Study, the authors argue for the existence of a single general dimension of psychiatric illness. They arrived at this conclusion by interviewing adults ages 18 to 38 at multiple time points about many types of emotional-behavioral symptoms and then testing various classification structures using statistical models called confirmatory factor analyses to see which model actually fit the data best. They also examined how different classification structures performed in terms of other factors such as personality, life impairment, developmental history, and brain integrity.
[For more of this story, written by David Rettew, go to http://www.psychologytoday.com...nsion-mental-illness]
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