The Structure of Common Mental Disorders

Abstract
COMORBIDITY among mental disorders is commonly observed in both clinical and epidemiological samples.1-5 The robustness of this observation is rarely questioned; however, what is at issue is its meaning. Is comorbidity "noise"—nuisance covariance that researchers should eliminate by seeking "pure" cases for their studies—or a "signal"—an indication that current diagnostic systems are lacking in parsimony and are not "carving nature at its joints?"