A Taxometric Investigation of Unipolar Depression in the National Comorbidity Survey.

Ongoing debate has questioned whether unipolar depression is a dimensional or categorical phenomenon. Although past studies using taxometric methods have supported a dimensional interpretation, each has suffered from methodological limitations. The present study was designed to overcome these limitations through reanalysis of the National Comorbidity Survey. Two indicator sets were constructed from the depression-relevant questions of the Composite International Diagnostic Interview. Participants who endorsed the lifetime occurrence of significant depressed mood or anhedonia (n=4,577) were submitted to 2 nonredundant taxometric procedures (maximum eigenvalue and means above minus below a cut), additional consistency tests, and recently developed simulation techniques. All results converged on a dimensional solution. The implications of these findings on assessment, treatment, and research design are discussed.