The trait‐state distinction between schizotypy and clinical high risk: results from a one‐year follow‐up
Authors: Chantal Michel, Rahel Flückiger, Jochen Kindler, Daniela Hubl, Michael Kaess, Frauke Schultze‐Lutter
Journal: World Psychiatry (2019)

Psychoses are severe, yet heterogeneous psychiatric conditions of multifactorial etiology. Both a clinical high-risk (CHR) condition and trait anhedonia (as part of the schizotypy construct) have recently been reported in an umbrella review published in this journal1 as promising clinical risk factors for early detection of psychosis. These results reflect the two main lines of phenomenological research in the field of early detection of psychosis prior to its first episode2: the clinical high-risk approach3 and the schizotypy approach4, 5. With few exceptions2, 6, these two approaches were so far examined for their psychosis predictive value independent of each other, as well as by different means in different populations: schizotypy by means of self-report scales in mostly non-clinical samples, and CHR criteria by means of clinical interviews in mostly clinical samples2. Schizotypy is regarded as a latent trait or personality organization, frequently assessed by the Wisconsin Schizotypy Scales (WSS)2, 7 (physical anhedonia, social anhedonia, perceptual aberration and magical ideation). The latter two scales were reported to load on the same factor as attenuated and transient positive symptoms as well as perceptive basic symptoms8, that, next to cognitive basic symptoms, are commonly used to define a symptomatic CHR state3. Supporting the assumption of the trait character of schizotypy, results from non-clinical samples showed relatively good stability of the WSS scores across short time periods9. In contrast, and supporting their conceptualization as state factors, CHR criteria and symptoms are rarely stable over time in clinical samples10. Yet, it is so far unknown whether CHR symptoms influence the report on WSS, especially with regard to the partly overlapping (attenuated) positive symptoms and the positive WSS2, 6, in clinical samples. To shed first light on this question, we examined the temporal stability as well as the interrelation of potential temporal changes of WSS and CHR symptoms over one year in 29 patients recruited at the Bern Early Detection and Intervention Centre for Mental Crises. At baseline, patients were 18±5 years of age on average (range: 9-27 years) and 41% were male. One patient (3%) already had a psychotic disorder, 22 (76%) fulfilled CHR criteria, and six (21%) received diagnoses unrelated to the psychotic spectrum. The Schizophrenia Proneness Instruments were used to assess the 14 basic symptoms included in the two basic symptom criteria3. The Structured Interview for Psychosis-Risk Syndromes was used to assess the five positive symptoms included in the symptomatic UHR criteria3. Schizotypy was assessed by the WSS. As required by the local ethics committee, patients and, if minors, their legal guardians gave informed consent for their anonymized clinical data to be used in scientific analyses and publications. Using SPSS 24, differences between baseline and follow-up (delta) of the mostly normally distributed sum scores were analyzed through dependent t-tests with bootstrapping to test for effects of potential outliers and reliability of results. These revealed significant temporal differences in basic symptoms (mean delta=3.45, t(28)=2.38, p=0.024) and positive symptoms sum scores (mean delta=2.00, t(28)=2.48, p=0.021). In contrast, differences in WSS scores remained non-significant: physical anhedonia (mean delta=1.55, t(28)=1.79, p=0.106), social anhedonia (mean delta=1.35, t(28)=1.68, p=0.107), magical ideation (mean delta=0.28, t(28)=0.40, p=0.691), and perceptual aberration (mean delta=0.62, t(28)=0.92, p=0.360). Furthermore, examining Pearson's correlations between the scales difference scores, we found a significant strong correlation only between magical ideation and perceptual aberration (r=0.506, p=0.005), and trend-level moderate correlations between physical anhedonia and both magical ideation (r=0.337, p=0.091) and perceptual aberration (r=0.319, p=0.073), as well as between the two CHR symptoms difference scores (r=0.328, p=0.083). Difference scores of WSS and CHR symptoms never correlated (r=0.012 to 0.306; p=0.969 to 0.106). In linear regression analyses, WSS difference scores were not predictive of CHR symptom difference scores, which, in turn, did not predict WSS difference scores. Our results strengthen the distinction between CHR symptoms and schizotypy in terms of independent state and trait factors and, thus, the notion that CHR symptoms occur on top of a heightened schizotypy, as suggested by the model by Debbané et al2. Furthermore, their independence support notions that the prediction of psychosis might be improved by their combination6. To this aim, physical anhedonia and social anhedonia, that constitute the negative schizotypy dimension, might be especially promising candidates. Negative schizotypy might be able to detect those people most likely to progress to a severe mental disorder among those at an already increased risk to experience psychotic or psychotic-like symptoms – detected by CHR criteria. This might explain why both anhedonia scales showed greater, though still non-significant, variation over time. Future studies on larger samples with longer follow-up and more assessment times are needed to explore the reliability of our findings, the potential specific relationships between trait and state factors, the potential patterns related to conversion to psychosis, and, ultimately, the role of these likely important risk factors of psychoses in their aetiology1.