Depression taxometric analysis

Haslam, N., Beck, A. T. (1994). Subtyping major depression A taxometric analysis. Journal of Abnormal Psychology, 103, 686-692. 

Ruscio, J., St Ruscio, A. M. (2000). Informing the continuity controversy A taxometric analysis of depression. Journal of Abnormal Psychology, 109, 473-487. 

The results were not completely consistent, but these findings seem to favor a dimensional model of depression. However, this may reflect inadequate indicator selection. Taxometric power analysis suggests this is not the case, but the power analyses may have presented an overly optimistic view of indicator quality. In addition, the construct validity of the indicators used in this study is unknown. The validity of the BDI and the MMPI Scale 2 are well established, but the authors used indicators derived from these instruments, not the scales themselves. We cannot assume that the indicators assessed depression as accurately as the original scales. In fact, we don t know whether the derived scales are reliable. It is possible that the indicators actually did not tap syndromal depression, but instead they tapped a closely related factor such as negative affect, and thus are largely irrelevant to the question about the taxonicity of depression per se. 

It also seems likely that some mental disorders (perhaps major depressive disorder) in their present form will fail to show evidence of taxonicity, but definitional refinement would help elucidate underlying taxa (e.g., melancholia). Thus, taxometrics may be able to serve as an impetus and a guide for revising the diagnostic system. Of course, taxometric methods alone are not sufficient to tackle this task and should be used in conjunction with dimensional methods, such as exploratory factor analysis. Dimensions provide the building blocks for construction of taxa, and research on the structure of psychopathology should integrate dimensional and taxometric methods. 

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