Psychotic disorders and schizophrenia-spectrum personality disorders (PD) with psychotic/psychotic-like symptoms are considerably linked both historically and phenomenologically. In particular with regard to schizotypal and schizotypal personality disorder (SPD), this is evidenced by their placement in a joint diagnostic category of non-affective psychoses in the InternationaI Classification of Diseases 10th Revision, (CD-10) and, half-heartedly, the fifth edition of Diagnostic and Statistical Manual of Mental Disorders, (DSM-5). Historically, this close link resulted from observations of peculiarities that resembled subthreshold features of psychosis in the (premorbid) personality of schizophrenia patients and their biological relatives. These personality organizations were therefore called "borderline (schizophrenia)" in the first half of the 20th century. In the 1970s, they were renamed to "schizotypal" and separated from psychotic disorders on axis-I and from other PD on axis-II, including modern borderline PD, in the DSM. The phenomenological and historical overlap, however, has led to the common assumption that the main difference between psychotic disorders and SPD in particular was mainly one of severity or trajectory, with SPD representing a latent form of schizophrenia and/or a precursor of psychosis. Thus, psychosis proneness and schizotypy are often assessed using SPD questionnaires. In this perspective-piece, we revisit these assumptions in light of recent evidence. We conclude that schizotypy, SPD (and other schizophrenia-spectrum PD) and psychotic disorder are not merely states of different severity on one common but on qualitatively different dimensions, with the negative dimension being predictive of SPD and the positive of psychosis. Consequently, in light of the merits of early diagnosis, the differential early detection of incipient psychosis and schizophrenia-spectrum PD should be guided by the assessment of different schizotypy dimensions.
Keywords: disorganized dimension; negative dimension; positive dimension; prediction; psychosis; schizotypal personality disorder; schizotypy.
The psychoses: cluster 3 of the proposed meta-structure for DSM-V and ICD-11.Psychol Med. 2009 Dec;39(12):2025-42. doi: 10.1017/S0033291709990286. Epub 2009 Oct 1. Psychol Med. 2009. PMID: 19796428 Review.
Schizotypal personality traits in nonpsychotic relatives are associated with positive symptoms in psychotic probands.Schizophr Bull. 2003;29(2):273-83. doi: 10.1093/oxfordjournals.schbul.a007004. Schizophr Bull. 2003. PMID: 14552503
Psychosis-predictive value of self-reported schizotypy in a clinical high-risk sample.J Abnorm Psychol. 2016 Oct;125(7):923-932. doi: 10.1037/abn0000192. Epub 2016 Sep 1. J Abnorm Psychol. 2016. PMID: 27583768
Schizotypal personality disorder.J Pers Disord. 2013 Oct;27(5):652-79. doi: 10.1521/pedi_2012_26_053. Epub 2012 Aug 28. J Pers Disord. 2013. PMID: 22928856
The role of schizotypy in the study of the etiology of schizophrenia spectrum disorders.Schizophr Bull. 2015 Mar;41 Suppl 2(Suppl 2):S408-16. doi: 10.1093/schbul/sbu191. Schizophr Bull. 2015. PMID: 25810055 Free PMC article. Review.