Diagnosing Major Depressive Disorder XI: A Taxometric Investigation of the Structure Underlying DSM-IV Symptoms

Psychopathologists have long debated the latent structure of mental disorders, and a number of researchers have suggested that depression may be best characterized as a continuous, rather than categorical, phenomenon. Nonetheless, attention has been drawn to limitations permeating existing research and the need for studies using more appropriate statistical methods developed expressly to tease apart taxonic (categorical) and dimensional (continuous) structural models. The present study examined the structure underlying the DSM-IV symptoms of major depressive disorder in a large outpatient sample rigorously assessed using semistructured clinical interviews. The results of a series of taxometric procedures and consistency tests supported a taxonic structural model, consistent with the only previous taxometric study of DSM-IV symptoms in an adult outpatient sample. In addition to the need for further replication and clarification, these results have implications for the assessment and diagnosis of major depressive disorder. Suggestions for several additional avenues of research are discussed.