Some suggestions for the DSM-5 schizotypal personality disorder construct

Abstract

This study relates to the schizotypal personality disorder (SPD) proposal of the upcoming fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) by investigating the construct validity of SPD as defined by DSM-IV in a large sample of patients from the Norwegian Network of Personality-Focused Treatment Programs (N = 2619), assessed by structured diagnostic interviews and the Longitudinal, Expert All Data standard. We investigated factor structure and psychometric properties of the SPD criteria, as well as co-occurrence patterns between SPD and other PDs. Thirty-six patients were diagnosed with SPD and 513 patients (21%) endorsed at least 2 schizotypal criteria. We found that 2 factors were specific for SPD, a cognitive-perceptual factor (ideas of reference, magical thinking, and unusual perceptual experiences) and an oddness factor (odd thinking and speech, constricted affect, and odd appearance or behavior). The criteria belonging to these factors had appropriate psychometric properties. The criteria of the cognitive-perceptual factor were more strongly associated with borderline personality disorder (PD) than with the other PDs. We did not find support for a consistent factor that reflected interpersonal problems. The criteria that used to be part of this factor (suspiciousness, lack of friends or confidants, and excessive social anxiety) performed poorly as specific SPD criteria. SPD was more strongly associated with antisocial PD and paranoid PD than with the other PDs. We suggest that ideas of reference should be included explicitly under the schizotypal facet of cognitive dysregulation in DSM-5, with less emphasis on the social phobic aspects of this feature. Furthermore, there should be more emphasis on the cognitive aspects of suspiciousness in SPD, and it should be considered to split up the affectivity criterion into constricted affect and inappropriate affect, with the latter type of affect being the expression of problems with intersubjective regulation. Finally, it is suggested that interpersonal dysfunction is secondary to the 2 primary SPD factors. Therefore, the SPD narrative should start by describing eccentricity and cognitive-perceptual aberrations rather than interpersonal difficulties.