Psychiatry Research 227 (2015) 283–289

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Ten-year stability of self-reported schizotypal personality features in patients with psychosis and their healthy siblings Lucía Moreno-Izco a, Ana M. Sánchez-Torres a, Ruth Lorente-Omeñaca a, Lourdes Fañanás b,c, Araceli Rosa b,c, Paola Salvatore d,e, Victor Peralta a, Manuel J. Cuesta a,n a

Psychiatric Unit B, Complejo Hospitalario de Navarra, Pamplona, Spain Unitat d’Antropologia, Departament Biologia Animal, Facultat de Biologia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain c Centro de Investigacion Biomedica en Red de Salud Mental (CIBERSAM), Universitat de Barcelona, Barcelona, Spain d International Consortium for Bipolar and Psychotic Disorders Research, Department of Psychiatry, McLean Hospital-Harvard Medical School, Belmont, MA, United States e Section of Psychiatry, Department of Neuroscience, University of Parma, Parma, Italy b

art ic l e i nf o

a b s t r a c t

Article history: Received 4 June 2014 Received in revised form 5 February 2015 Accepted 22 February 2015 Available online 31 March 2015

Schizotypal personality disorder (SPD) symptoms or features are common in patients with psychosis and their healthy relatives. However, the long-term stability of these SPD features and therefore their constituting enduring traits underlying vulnerability to psychosis remain to be clarified. Thirty-two patients with psychotic disorders and 29 of their healthy siblings were included from the long-term follow-up study of 89 nuclear families. Participants were clinically assessed by means of a semistructured diagnostic interview, whereas the Schizotypal Personality Questionnaire-Brief (SPQ-B) was applied for the self-assessment of SPD symptoms. The assessments were carried out upon admission to the study and at follow-up, about 10 years later. The patients had higher scores than their siblings on the SPQ-B both at baseline and follow-up. In addition, self-reported SPD symptoms remained stable over time in total scores and in all the SPQ-B subscores, except for the SPQ-B Disorganization subscale. Selfreported SPD symptoms were stable over the long term among patients with psychotic disorders and their healthy siblings. This finding provides new support for including the SPD construct as a trait measure for studies addressing both vulnerability to psychosis in first-degree relatives of patients with psychosis and long-term persistence of symptoms in patients suffering from psychosis. & 2015 Elsevier Ireland Ltd. All rights reserved.

Keywords: Psychosis Schizophrenia Relatives Personality disorders

1. Introduction The finding of prevalent psychotic-like experiences in the general population seems to support the validity of the continuum hypothesis of psychosis (Fonseca-Pedrero et al., 2009; Nelson and Yung, 2009). On the other hand, the concept of schizotypal personality structure, originally stemmed from the classic framework of schizotaxia and schizotypy (Meehl, 1989; Rado, 1953), and later incorporated as a personality disorder in contemporary psychiatric taxonomy, rather appears to corroborate the hypothesis of a distinctive psychopathological deviation from healthy conditions in first-lifetime emerging psychosis. In addition, Meehl's schizotaxia– schizotypy model paved the way to the conceptualization of “psychosis proneness” by Chapman and Chapman (1985). Despite the fact that schizotypy has been considered taxonic in North American tradition, the European view has mainly favored a fully dimensional

n

Corresponding author. Tel./fax: þ 34 848 422488. E-mail address: [email protected] (M.J. Cuesta).

http://dx.doi.org/10.1016/j.psychres.2015.02.020 0165-1781/& 2015 Elsevier Ireland Ltd. All rights reserved.

approach to this construct (Kwapil and Barrantes-Vidal, 2012). Therefore, while schizotypy has come to imply a multidimensional neurodevelopmental and psychopathological vulnerability to schizophrenia, schizotypal personality disorder reflects a nosological category of an Axis II diagnosis within the schizophrenia spectrum disorders (Kwapil and Barrantes-Vidal, 2012). Assuming that schizotypal personality disorder might represent not only a categorical diagnostic realm but also a key multidimensional psychopathological construct, schizotypal personality features may be potential vulnerability indicators for schizophrenia and psychosis (Horan et al., 2008). In this regard, several studies have provided interesting data on schizotypal phenomenology complex relationship with psychosis. Schizotypal personality disorder features have been associated with the risk of developing schizophrenia (Compton et al., 2009; Miller et al., 2002), as well as with neurocognitive and psychosocial impairment in schizophrenia patients (Compton et al., 2009; Gooding et al., 2006), and schizotypal personality disorder symptoms have been found to be more common in relatives of patients with psychosis (Compton et al., 2009; Kendler et al., 1995).

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Following Nuechterlein and Dawson (1984) a valid and reliable candidate indicator of vulnerability to psychotic disorders should show evidence of a clear abnormality as compared to the general population, and that the abnormality itself be an enduring feature regardless of patients clinical status. In addition, the pattern of variation in severity of the abnormality in relation to the level of variation in symptoms over the course of the psychotic illness is essential to differentiate between stable, mediating and episoderelated vulnerability markers (independent, partially dependent and dependent on the acute symptomatology, respectively) (Horan et al., 2008). In addition, a significant number of self-report rating scales have been developed to define the concept of schizotypal personality structure with a purely dimensional approach including the Physical and Social Anhedonia Scales (Chapman et al., 1976), the Perceptual Aberration Scale (Chapman et al., 1978) and the Magical Ideation Scale (Eckblad and Chapman, 1983), among others (Compton et al., 2007). However, the use of these scales may have some drawbacks such as their length and the fact that they do not represent the nine features of SPD described in DSM-III-R (Raine, 1991) while exploring the classic psychopathological construct of schizotypy and schizotaxic-derived vulnerability to schizophrenia. To solve the latter limitation, Raine developed the Schizotypal Personality Questionnaire (SPQ), a 74-item self-report instrument, based on DSM-III-R criteria for Schizotypal personality disorder (SPD) and including nine subscales to evaluate the nine features of SPD listed in DSM-III-R (Raine, 1991; Raine and Benishay, 1995). This questionnaire has shown to have a three-factor structure, namely Cognitive-Perceptual Deficits (Ideas of Reference, Magical Thinking, Unusual Perceptual Experiences and Paranoid Ideation), Interpersonal Deficits (Social Anxiety, No Close Friends, Blunted Affect, Paranoid Ideation), and Disorganization (Odd Behavior, Odd Speech) (Axelrod et al., 2001). A confirmatory factor analysis of the nine subscales demonstrated that these three factors best represent schizotypal personality construct, and seem to be equivalent to the three factors (positive, negative and disorganized) that have been identified for schizophrenic symptomatology (Arndt et al., 1991; Raine and Benishay, 1995). Despite there is a consensus in that schizotypy is a multidimensional construct and that the Raine's three-factor model is the most replicated, not all studies confirmed it and there are other studies supporting a four-factor model in the SPQ (Fonseca-Pedrero et al., 2014; Stefanis et al., 2004) as well as a five-factor model at an item-level of the SPQ in a large sample of undergraduate students (Chmielewski and Watson, 2008). Furthermore, Raine and Benishay (1995) developed a shorter instrument, the Schizotypal Personality Questionnaire-Brief (SPQB) that may be used when the time for evaluation is limited or to screen a large number of individuals for predisposition to SPD. This is a self-report scale, based on the SPQ, containing 22 items and subscales for the same three factors. It has a good criterion validity (mean r ¼0.62) and the internal and test–retest reliability appear to be reasonable (r ¼0.72–0.95) (Raine and Benishay, 1995). The dimensional structure of the SPQ-B has been addressed in different studies in non-clinical populations reporting different solutions ranging from two (Aycicegi et al., 2005), and three (Axelrod et al., 2001; Compton et al., 2007, 2009; Mata et al., 2005) to four factors (Cohen et al., 2010; Fonseca-Pedrero et al., 2010). Despite the SPQ-B is widely used to identify schizotypy that hypothetically may increase the vulnerability to schizophrenia in non-patient individuals, little is known about whether patients with psychosis show either stable or changing scores on these scales across different clinical states. This approach has been used with the Chapman's and colleagues Psychosis Proneness Scales to clarify the extent to which their psychometric vulnerability indicators (positive and negative schizotypy) represent state or trait phenomena (Horan et al., 2008).

Moreover, there are few studies on schizotypal personality symptoms that include patients with schizophrenia. Vollema and Postma (2002) found support for the positive dimension of the SPQ as a vulnerability marker of the disease by examining schizophrenia patients, siblings of schizophrenia probands and healthy controls. Also, Horan et al. (2008) examined the longitudinal patterns of the Chapman's and colleagues scales in recentonset schizophrenia patients to test specifically their changes over time and across clinical states. As positive and negative symptoms vary diachronically from the acute episode to the remission state, and providing that schizotypal symptoms are defined on the basis of diminished forms of the symptoms of psychosis, it could be relevant to evaluate whether these self-reported schizotypal symptoms are stable over time from the acute episodes throughout long-term follow-up phases. To the best of our knowledge, the stability of SPD features over time has been explored in a few studies (Ericson et al., 2011; Meyer and Hautzinger, 1999; Squires-Wheeler et al., 1991) and never evaluated using SPQ-B. The aim of the current study was to evaluate the SPQ-B stability in a sample of patients with psychotic disorders and their healthy siblings over 10 years of follow-up. We hypothesized that patients with psychosis would have higher scores than their healthy siblings on the SPQ-B and that, based on SPD being an enduring trait, scores would remain stable over time in both groups.

2. Methods 2.1. Participants The initial sample population included 89 nuclear families recruited in Virgen del Camino Hospital in Pamplona, Spain. These nuclear families comprised one member with a psychotic disorder, who was recruited from consecutive admissions to the Acute Psychiatric Unit for psychotic exacerbations, between 1999 and 2001, one healthy sibling and both parents. Patients underwent a comprehensive evaluation using a semi-structured diagnostic interview (The Comprehensive Assessment of Symptoms and History, CASH) (Andreasen, 1992). The CASH interview includes the positive and negative symptoms rating scales, and in this study was combined with other instruments for the assessment of motor and psychopathological dimensions and cognitive phenomena, as described in detail elsewhere (Rosa et al., 2004). Parents and healthy siblings of patients were screened using an abbreviated version of the CASH to evaluate and rule out a history of psychiatric disorders in proband's parents and siblings respectively. For this study, we included only those patients and their siblings who agreed to undergo a second evaluation in 2009. This sample comprised 42 patients and 35 of their siblings (43% of the initial sample). Reasons for discontinuation of participants included death (8 pairs; 7 patients and 1 sibling), traumatic brain injury (1 patient), change of residence and failure to contact them (11 pairs), and declining to participate to the follow-up assessments (27 patients and 34 siblings). For the present research report, we analyzed data gathered from 32 patients and 29 of their siblings, who completed the clinical assessments required for this study including SPQ-B at baseline and follow-up. The average time between initial and final evaluation was 9 years and 6 months (range: 7–11 years). Demographic data and diagnostic categorization of study subjects are shown in Table 1. All patients suffered from a psychotic episode and they did not fulfill Schizotypal personality disorder diagnostic criteria. Those patients with a mood disorder diagnosis (n¼ 4) had mood-incongruent psychotic affective symptoms. All subjects gave written informed consent to participation in the research project and the study protocol was approved by the local ethics committee.

2.2. Procedures Participants were evaluated using the Schizotypal Personality Questionnaire-Brief (SPQ-B) (Raine and Benishay, 1995) at baseline and at 10-year follow-up. As we mentioned previously, SPQ-B is a brief, 22-item self-report screening instrument, its estimated administration time being only 2 min. This questionnaire is based on the SPQ and results are a total scale score and scores for three subscales (Cognitive-Perceptual Deficits, Interpersonal Deficits, and Disorganization). We used a Spanish version that has previously been validated in adolescents (Fonseca-Pedrero et al., 2010, 2009).

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of age (26.84 7 5.63 vs. 26.81 75.86; t¼0.03, p ¼0.78), years since illness onset (5.5 75.93 vs. 4.54 75.09; t¼ 0.81, p ¼0.42), years of education (12.29 73.03 vs. 11.30 73.56; t ¼1.32, p ¼0.80), Global Assessment of Functioning Scale (GAF; APA, 2000) score (87.06 710.35 vs. 83.667 11.83; t¼1.35, p ¼0.79), or gender distribution (χ2 ¼4.05, p ¼0.44). In the siblings group, there were no significant differences between those who participated in 2009 and those who did not, in terms of age (29.07 75.72 vs. 26.91 76.99; t¼ 1.45, p¼ 0.12), years of education (13.09 73.53 vs. 12.25 74.15; t¼0.83, p ¼0.35), GAF score (95.94 77.40 vs. 92.637 7.89, t¼ 1.47, p ¼0.21), or gender distribution (χ2 ¼0.17, p¼ 0.67). Patients showed significantly higher scores than their healthy siblings on all SPQ-B scores, namely SPQ-B total and for the three subscales (Cognitive-Perceptual [cp], Interpersonal [int], and Disorganization [dis]). Repeated measures ANOVA demonstrated a significant effect based on groups for SPQ-B total and the three subscales. Time, however, did not have a significant effect, except on the SPQ-B Disorganization subscale, for which scores were higher at baseline. Furthermore, interactions between time and group were not significant. Overall effect sizes for these interactions were small (Table 2). When applying linear fixed models to the SPQ-B total scores and cognitive perceptual and interpersonal dimensions, the results did not change with respect to the ones obtained with the ANOVAs. SPQ-B total scores and cognitive-perceptual and interpersonal deficits dimensions did not show significant group-bytime interaction, and only significant differences regarding group but not time after controlling for the effect of membership to a family. Disorganization SPQ-B scores showed significant differences in group and time, but not in the group-by-time interaction (Supplementary Table 1). In Table 3, we report the results of Cronbach's Alpha coefficients including SPQ-total t0  t1 0.57 for patients and 0.67 for siblings, as well as SPQ-cp t0–t1 0.51 and 0.75, SPQ-int t0–t1 0.52 and 0.47, and SPQ-dis t0–t1 0.74 and  0.10, for patients and siblings respectively. Pearson coefficient correlations between lifetime psychopathological dimensions and SPQ-B dimensions for patients and their siblings were carried out (Supplementary Table 2). There was a relative independence of SPQ-B scores in relation to lifetime positive, negative and disorganization dimensions except for significant associations between lifetime positive symptomatology and SPQ-B cognitive-perceptual dimension in the follow up of patients (r ¼0.54, p r0.001) (p Value after Bonferroni correction for multiple test 3  8 was set at p r0.001).

In addition, positive, negative and disorganization dimensions were calculated for patients and their healthy siblings by means of the resulting scores in the CASH interview.

2.3. Data analysis Comparisons of demographic characteristics between groups were made by means of the Mann–Whitney U and chi-squared tests. Repeated measures analysis of variance (ANOVA) was performed to assess time and group effects as a function of SPQ-B total and subscale scores. The assessment time point was the within-subject factor-baseline (t0) and follow-up (t1)- and the group membership was the between-subject factor (patients and siblings). Effects sizes were measured by partial Eta square indexes. To examine the stability of the symptoms measured by SPQ-B scale, we used Cronbach's Alpha coefficients. To investigate the relationship between SPQ-B scores and diagnostic group (patients and siblings) and its evaluation over time, linear mixed models were fitted, one per each SPQ-B score (total score and 3 subscales). Each model had, as response variable, the SPQ-B score at each evaluation time (baseline and follow-up) and, as fixed effects, both the corresponding evaluation time and the SPQ-B scores at that time. A random effect to account for within family association was also included. The interaction term between the SPQ-B scores and evaluation time was added to assess whether the association between SPQ-B scores and diagnostic group changed over time. Influence of lifetime psychopathological dimensions on the SPQ-B scores of patients and siblings were accounted for by Pearson coefficient correlations.

3. Results Patients and healthy siblings did not significantly differ in terms of age, gender distribution or years of education (Table 1). There were no significant differences between patients who participated in the study in 2009 and those who did not in terms Table 1 Socio-demographic, clinical and diagnostic variables of patients and unaffected siblings at follow-up.

Age Gender (%men/women) Years of education Age at onset Years since illness onset Number of episodes Hospitalizations DSM-IV diagnoses n (%) Schizophrenia Schizoaffective disorder Bipolar disorder Brief psychotic disorder

Patients (n ¼32)

Healthy siblings (n¼ 29)

P. vs. S.

36.47 (5.46) 65.6/34.4 13.28 (4.1) 21.34 (5.72) 5.50 (5.93) 3.31 (2.63) 2.75 (2.36)

38.48 (6.01) 41.4/58.6 13.62 (3.59)

p¼ 0.175 p¼ 0.058 p¼ 0.733

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19 (59.4) 8 (25) 4 (12.5) 1 (3.1)

CASH lifetime dimensions Positive dimension 2.7071.20 Negative dimension 2.46 7 1.35 Disorganization 1.417 0.92 dimension

4. Discussion Our results support two main findings. First, patients with psychosis did have higher scores than their healthy siblings, both

P.¼ patients; S. ¼siblings.

Table 2 Means and standard deviations (SD) of SPQ-B at baseline and follow-up. Repeated measures ANOVA between patients and siblings.

SPQtotal SPQcp SPQint SPQdes n

Patients (n¼ 32)

Siblings (n ¼29)

ANOVAnn (time effect)

Baseline

Follow-up

Baseline

Follow-up

F (p Value)

Effect size (η2)

F (p Value)

9.56 2.68 4.34 2.56

8.37 2.68 4.18 1.50

3.83 1.06 1.82 0.93

3.10 0.68 2.10 0.31

2.59 0.65 0.03 17.82

0.042 0.011 0.001 0.232

34.22 26.04 24.61 18.17

(5.14) (2.05) (2.33) (1.96)

Significant at po 0.05. d.f. ¼ 1, 59.

nn

(5.32) (2.08) (2.64) (1.74)

(3.47) (1.13) (1.85) (1.19)

(2.56) (0.89) (1.83) (0.71)

(0.11) (0.42) (0.85) ( o 0.001)n

ANOVAnn (group effect)

( o 0.001)n ( o 0.001)n ( o 0.001)n ( o 0.001)n

ANOVAnn (time x group effect)

Effect size (η2)

F (p Value)

Effect size (η2)

0.367 0.306 0.294 0.235

0.15 0.65 0.43 1.22

0.003 0.011 0.007 0.020

(0.69) (0.42) (0.51) (0.27)

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Table 3 Cronbach's Alpha coefficients of the SPQ-B and dimensions in the three-factor solution (Raine and Benishay, 1995) and in the two-factor solution (Aycicegi et al., 2005). a. SPQ-B dimensions of Raine and Benishay (1975) three factor solution

SPQtotal t0–t1 SPQcp t0–t1 SPQint t0–t1 SPQdis t0–t1

Patients (n¼32)

Siblings (n¼ 29)

0.57 0.51 0.52 0.74

0.67 0.75 0.47  0.10

b. SPQ-B dimensions of Aycicegi et al. (2005) two factor solution

SPQpos t0–t1 SPQneg t0–t1

Patients (n¼32)

Siblings (n¼ 29)

0.54 0.58

0.50 0.0

SPQcp ¼ SPQ cognitive-perceptual dimension; SPQint ¼SPQ interpersonal dimension; SPQdis¼ SPQ disorganization dimension; t0¼ baseline; t1¼ follow-up. SPQpos ¼ SPQ positive dimension; SPQneg: SPQ negative dimension.

on the SPQ-B total scale score and on the three subscales (Cognitive-Perceptual, Interpersonal, and Disorganization), as we hypothesized at the outset. This was an expected finding which could only be related to the fact that schizotypal symptoms may represent attenuated expressions of the psychotic symptoms. However, SPQ-B scores at baseline were obtained close to an acute episode, which usually shows high severity of positive, negative and disorganization symptoms that decreases during follow-up. Yet, this was not the pattern of SPQ-B ratings that showed similar scores in the follow-up even among patients. Moreover, lifetime psychopathological dimensions showed only one significant association with SPQ-B scores, namely, between lifetime positive dimension and cognitive perceptual dimension but not with the SPQ-B interpersonal and disorganization dimensions in the followup in the patients group (Supplementary Table 2). These results are in agreement with previous research that has shown that the construct of SPD is genetically related to schizophrenia (Compton et al., 2007; Kendler et al., 1993), and therefore individuals who have high scores for SPD features have a higher risk of developing the illness (Catts et al., 2000; Compton et al., 2007; Fanous et al., 2001; Vollema and Postma, 2002). On the other hand, unaffected first-degree relatives of schizophrenia patients show greater prevalence of these quantitative SPD abnormalities than the general population, which suggests that they could constitute intermediate phenotypes of psychotic diathesis (Compton et al., 2007). Second, SPQ-B total score and Cognitive-Perceptual and Interpersonal subscales scores remained stable over time in both groups, whereas this was not the case for SPQ-B Disorganization subscale, for which scores were higher at baseline. The stability of SPQ-B scores and their relative independence of psychopathological dimensions throughout the follow-up period suggested that schizotypal personality disorder symptoms may be stable vulnerability indicators for psychotic disorders (Horan et al., 2008). The lack of stability of the Disorganization subscale scores reported in this study might be related to the still controversial independence of the disorganization dimension within the intrinsic dimensional structure underlying the SPQ-B. The factor structure of the SPQ-B has been widely investigated with exploratory factor analysis of the 22 items of the SPQ-B being conducted in several studies (Compton et al., 2009). Axelrod et al. (2001), investigating samples of adolescent psychiatric inpatients, have pointed to the possibility that only two factors be sufficiently represented in the SPQ-B because of the limited convergent and discriminant validity of the SPQ-B Disorganization subscale. This is in agreement with other studies reporting a two-factor structure

comprising schizotypal positive and negative symptoms with the disorganization symptoms loading on these two factors (Aycicegi et al., 2005). Therefore, the reported inconsistency in the Disorganization subscale led us to both explore whether it could be related to the three-factor structure of the SPQ-B, as well as test the two-factor solution in our data. Nevertheless, the examination of the results of the two-factor solution did not improve the internal consistency coefficients of SPQ-B dimensions of both patients and siblings. Although most studies reporting a two-factor structure have been carried out in samples of undergraduate students, there is one study conducted in a similar population which found the three core symptom dimensions of Cognitive-Perceptual, Interpersonal deficits, and Disorganization (Mata et al., 2005). On the other hand, Compton et al. (2007) examining relatives of patients with schizophrenia-spectrum disorders and non-psychiatric controls by confirmatory factor analysis, found a three-factor solution with reasonably good fit indices even though also the one-factor solution provided an equally good fit. However, at least 14 studies on varied and independent samples of patients have confirmed a three-factor solution to be the best (Ericson et al., 2011), and this was the rationale for using this instrument in our study. In addition, the three-factor solution is in agreement with the original description of the SPQ by Raine and Benishay. In their study, however, the criterion validity for the disorganization factor was lower than for the other subfactors (Cognitive-Perceptual and Interpersonal) and this might explain our inconsistent results regarding this subscale. The authors recommended completing the evaluation using all disorganization items from the SPQ, because of the weaker conceptual and empirical basis of the disorganization factor (Raine and Benishay, 1995). Moreover, Chmielewski and Watson (2008) raised several questions concerning the low external validity of the three-factor model of the full SPQ in relation to other personality and symptomatology measures, and found that the short-term test re-test was lower than expected in their sample of undergraduate students. Also, the lack of stability of Disorganization subscale scores, that we found, could be interpreted in light of phenomenological psychopathology as the indication that oddness of behaviors and speech conveyed by the Disorganization dimension of the SPQ-B might constitute an epiphenomenal and, therefore, not nuclear quality of subjective expressions of conduct and language. On the other hand, the truly core schizotypal personality abnormalities which concern the self- and reality awareness (Parnas et al., 2005) would factor-load on the other two subscales (Cognitive-Perceptual and Interpersonal). In particular, as Sass (2011) has interestingly

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pointed out eccentricity and oddness marking schizophrenic “infrastructure” of action and experience might secondarily originate from what Blankenburg (1971), (2001) had defined as the core schizophrenic disturbance that is a loss of common sense and natural selfevidence in grasping the self and reality (Sass, 2011). The self-assessment procedures for SPD symptoms or signs may entail methodological problems related to the difficulty of ascertaining those features, as well as accounting for discrepancies with clinician-assessed scales. Compton et al. (2007) examined the association of the SPQ-B and the nine researcher-assessed items of the SPD module of the Structured Clinical Interview for DSM-IV Axis II Personality disorders (First et al., 1997) and concluded that, although correlations between the two scales were moderate, the findings suggested adequate criterion validity. The SPQ has shown to be an appropriate instrument for the evaluation of SPD features in patients' relatives and general population (Bergman et al., 2000; Cochrane et al., 2012; Mata et al., 2000; Siever and Davis, 2004; Torti et al., 2013). Moreover, the SPQ-B is a brief selfreport scale modeled on DSM-III-R criteria for SPD and its use in patient population is not exceptional (Rossi and Daneluzzo, 2002; Schurhoff et al., 2005; Vollema and Postma, 2002). However, in the case of patients the psychopathological features that are being explored by the questionnaire might not easily be disentangled from schizophrenic symptoms. In this regard, the relationship between SPD features and schizophrenic symptoms and its evaluation in subjects with a stable diagnosis of schizophrenia still remains a challenging theoretical question that should be addressed by means of the study of patients longitudinally across different clinical stages (Horan et al., 2008). This theoretical issue is particularly difficult to address because none of the three fundamental conceptualizations of the relationship between schizophrenia and pre-schizophrenic constitutions/temperaments, personality structures, or vulnerability constellations, including Kraepelin' and Bumke's identity model, Kretschmer' and Bleuler's continuity/transition model, and Ewald', Jaspers' and Schneider's transformation/discontinuity model, has proven to be more reliable and valid than the others. Nevertheless, following Bleuler' and Kretschmer's continuity/ transition perspective, many researchers more recently hypothesized that schizophrenia symptoms are the exaggeration of SPD features (Raine, 1991). In addition, a resemblance between SPD symptoms and psychotic phenomenology was also found in the factor structure of both SPD phenomenology and psychotic symptomatology as the three identifiable factors underlying SPD construct broadly correspond to the positive, negative and disorganized dimensions of schizophrenia psychopathology (Fonseca-Pedrero et al., 2011; Wuthrich and Bates, 2006). It is interesting to emphasize that patients suffering from schizophrenia and other psychoses can reliably describe or report with an accurate level of clarity subtle subjective experiences even after long years of illness and during chronic states. Research on basic symptoms and basic stages, as well as on anomalous subjective phenomena of the self has been carried out since the 60's (Chapman, 1966; Freedman and Chapman, 1973; Gross and Huber, 1985, 1986; Huber and Gross, 1989; Huber et al., 1975; Klosterkotter et al., 2011; Parnas et al., 2003). Overall, these studies have shown that schizophrenia patients are not psychotic for most of the time of their illness course, and instead are often able to perceive, communicate and cope with a broad range of subjective disturbances and deficits of thought, perception, mood, emotional resonance, vital drive, language, psychomotor activity, volition, and bodily sensations which represent their fundamental psychopathological vulnerability susceptible to transitions toward first-rank symptoms and other full-blown psychotic phenomena. The application of instruments like the SPQ-B is far less complex to grasp by the individual than an interview with the Bonn Scale for the Assessment of Basic Symptoms (BSABS) (Gross et al., 1987) or the EASE

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(Examination of Anomalous Self-experience) (Freedman and Chapman, 1973; Parnas et al., 2005) which are usually successfully administered in schizophrenia patients even over several years of follow up of their illness course. Therefore, schizophrenia patients are also expected to provide highly reliable and insightful self-reports of SPD features as assessed with the SPQ-B. There are few studies addressing the stability of SPD symptoms over the long term. Squires-Wheeler et al. (1991) assessed SPD features at two points in time for three groups of offspring defined by the psychiatric diagnosis of their parents as schizophrenic disorders, affective disorders, and healthy controls. The aim of the study was to confirm that the SPD features, especially in those cases with a familial relationship with schizophrenia, were more severe on an initial, cross-sectional assessment, and stable over time. The authors showed that greater numbers of SPD features at the initial time were associated with an increasing probability of identifying a stable case. However, this stability was not only specific to offspring of parents with schizophrenic disorders (Squires-Wheeler et al., 1991). Further support to the longitudinal stability of SPD features was reported by Ericson et al. (2011) in a sample of adolescent twins. These authors examined the longitudinal genetic and environmental stability of SPD symptoms between the ages of 11 and 16 years using the Schizotypal Personality Questionnaire-Child version (SPQ-C). SPD features had been examined previously in the short-term using scores of Physical Anhedonia, Magical Ideation, and Perceptual Aberration scales in a two-year follow-up study conducted by Meyer and Hautzinger (1999) in a non-collegestudent sample. The authors showed that stability was relatively high for Physical Anhedonia, but not for Magical Ideation and Perceptual Aberration. The correlation of the psychosis proneness scales with SPD features was stronger than that with the other personality disorders symptoms. Prospectively, only Magical Ideation was observed to be a significant predictor of schizotypal and paranoid personality disorders features, and therefore able to serve as a sensitive and specific indicator for assessment of psychosis proneness in spite of its potentially inherent instability (Meyer and Hautzinger, 1999). In the research conducted by Ericson few years later, all SPQ-C subscales (Cognitive-Perceptual, Interpersonal-Affective and Disorganization) within assessment points were significantly correlated with each other, giving a first indication of longitudinal stability. Moreover, according to the results of a multivariate model, SPD features appeared to be notably stable over the course of development whereas other later genetic and environmental processes seemed to play an important role in the developmental phases. In line with this finding, the authors concluded that SPD construct, a potential vulnerability marker for schizophrenic psychosis, might be primarily influenced by genetic and non-shared environmental factors (Ericson et al., 2011). Several limitations need to be considered when interpreting the results of the present study. Firstly, ideally SPD features in patients with psychosis should be assessed, as any other premorbid characteristics, before illness onset and in a longitudinal prospective fashion. Thus influence of schizophrenic symptoms on the SPQ-B could not be discarded. However, the aim of this study was focused more on the comparative stability of the selfreported scores of schizotypal personality features in patients with psychosis and their siblings than on the specific assessment of schizotypal personality symptoms. Moreover, lifetime psychopathological dimensions showed a relative independence of SPQB dimensions in both patients and their siblings. Secondly, when considering the assessment of schizotypal personality features it is clearly stated that self-reported measures seem to be less effective, particularly in describing and defining those signs and psychopathological phenomena that necessarily require direct

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examination, such as disturbances of affect, behavior and cognitive slippage, than those measures derived from clinicianadministered interviews (Kendler et al., 1996; Vollema and Postma, 2002). However, what it is relevant here is that selfperceptions about schizotypal personality features in patients with psychosis and their siblings can be not only reliably assessed in cross-sectional assessments but also appear to be stable over the long term. And finally, as regards thorough design of future research studies, the inclusion of families that are not affected by psychotic disorders could support better investigation and comparison of SPQ-B scores of healthy siblings of patients with psychosis and those in the general population. In conclusion, self-assessed SPD features remained stable over the long term in patients with psychotic disorders and their healthy first-degree relatives. Specifically, both groups showed high stability on the SPQ-B, total and Cognitive-Perceptual and Interpersonal subscale scores, though not on the SPQ-B Disorganization subscale score. Our results suggest that self-assessed SPD symptoms are stable over time, and add evidence to support the theory of an enduring schizotypal personality trait underlying vulnerability to schizophrenic psychosis. Ultimately, the thorough examination and measurement of self-reported core dimensions of schizotypal personality traits could be useful for the identification and definition of reliable and valid endophenotypes in the early assessment of psychosis proneness.

Contributors Manuel J. Cuesta, Victor Peralta and Lourdes Fañanas designed the study and supervised the draft completion. Manuel J. Cuesta, Victor Peralta and Araceli Rosa collected the clinical data. Lucia Moreno managed the literature searches, analyzed the data and wrote the first draft of the manuscript. Ana M. Sánchez-Torres and Ruth Lorente-Omeñaca contributed to literature searches and data analyses. Araceli Rosa and Paola Salvatore cooperated in comments to the definitive version of the manuscript. All authors contributed to and approved the final draft of the paper.

Conflict of interest None.

Acknowledgment This study was partly funded by the Plan Nacional sobre Drogas (Grant 2008/I/030), the Department of Health of the Government of Navarra (Grant 101/11) and the Carlos III Health Institute of the Spanish Economic Affairs and Competitiveness (ERDF Funds) (Grants PI08/1026; PI11/02831). We thank to the Comission at per a Universitats i Recerca del DIUE (2009SGR827), Carlos III Health Institute and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM). We also thank the subjects who took part in this study.

Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.psychres. 2015.02.020.

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