FROM SCHIZOTYPAL PERSONALITY TO SCHIZOTYPAL DIMENSIONS: A TWO-STEP TAXOMETRIC STUDY

Objective: Various studies have explored the latent structure of schizotypy as conceptualized by Meehl, using Chapman scales. Conversely, a few studies have examined the latent structure of schizotypal personality as described by the nine DSM diagnostic criteria (unchanged from DSM-III-R to DSM-IV-TR). Therefore, it is not clear if this construct has to be considered as categorical or dimensional. Method: A taxometric analysis (MAMBAC, MAXCOV) was performed in a sample of 400 undergraduate students using the Schizotypal Personality Questionnaire (SPQ), a DSM-based self-report. This procedure represents one of the most powerful techniques to examine the latent structure of a construct. In a second research phase, we separately analyzed the latent structure of different schizotypal personality dimensions, detected by an item-level factor analysis. Results: The first finding of this study was that schizotypal personality, as assessed by the SPQ, is best conceptualized as a dimensional, not categorical, construct. Taxometric analyses, performed on three of the four SPQ factors (Unusual Beliefs and Experiences, Mistrust, Social Anhedonia, and Eccentric/Odd Behavior), yielded taxonic findings only for the Unusual Beliefs and Experiences construct, with a MAXCOV base rate of.11. Instead, the other two examined construct (Mistrust and Social Anhedonia) were more consistent with a dimensional underlying structure. Finally, we found that the taxonic group membership increased significantly the probability of having a first-degree relative with a diagnosis of schizophrenia. Conclusions: Our results suggest that positive schizotypy (as assessed by the SPQ subscales Magical Thinking and Unusual Perceptual Experiences) may be a phenotype for genetic investigation of schizophrenia. Our results emphasize the central role of positive schizotypy in comprehending etiopathogenetic mechanisms underlying schizophrenia