Are Negative Symptoms Dimensional or Categorical? Detection and Validation of Deficit Schizophrenia With Taxometric and Latent Variable Mixture Models.
Studies have supported the validity of the deficit form of schizophrenia (ie, people with primary and enduring negative symptoms). A test of whether that group is a true taxon-that is, a distinct, discontinuous group-has yet to be conducted and the underlying structure of negative symptoms as categorical or dimensional remains undetermined. The present study examined the latent structure of negative and deficit symptoms to determine if a nonarbitrary boundary distinguishes deficit from nondeficit forms of schizophrenia (ie, whether these symptoms reflect a continuous or categorical variable). Schedule for the Deficit Syndrome ratings of 789 individuals with a psychotic disorder were submitted to taxometric and latent variable mixture analyses to test categorical vs dimensional hypotheses of negative symptoms and deficit schizophrenia. Analytic models favored a taxonic structure of negative symptoms and the validity of the deficit/nondeficit classification scheme. Taxometric classification outperformed clinician-based deficit/nondeficit classification in its association with summer birth, male sex, premorbid adjustment, neurocognition, and psychosocial functioning. Within taxon and complement classes, severity scores remained significant predictors of premorbid adjustment, neurocognition, and psychosocial functioning. Thus, although a categorical approach is validated, a hybrid categorical-dimensional conceptualization of negative symptoms also has validity for the prediction of external variables.
Department of Psychiatry, Weill Cornell Medical College, White Plains, NY; Department of Psychiatry and Health Behavior, Medical College of Georgia, Georgia Regents University, Augusta, GA; aoa9001@med.cornell.edu.
Anthony O
AO
Ahmed
Department of Psychology, Binghamton University, Binghamton, NY;
Gregory P
GP
Strauss
Department of Psychiatry; Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD;
Robert W
RW
Buchanan
Department of Psychiatry, University of Nevada School of Medicine, Reno, NV.
Brian
B
Kirkpatrick
Department of Psychiatry; Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD;
William T
WT
Carpenter
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data*; D011618:Psychotic Disorders / Q000145:classification* / Q000175:diagnosis; D012559:Schizophrenia / Q000145:classification* / Q000175:diagnosis; D012720:Severity of Illness Index
classification; deficit/negative symptoms taxon; hybrid categorical-dimensional model; schedule for the deficit syndrome