Schizotypal Signs Research Articles

Brain structural correlates of schizotypal signs and subclinical schizophrenia nuclear symptoms in healthy individuals.

Subclinical psychotic-like experiences (PLE), resembling key symptoms of psychotic disorders, are common throughout the general population and possibly associated with psychosis risk. There is evidence that such symptoms are also associated with structural brain changes. In 672 healthy individuals, we assessed PLE and associated distress with the symptom-checklist-90R (SCL-90R) scales 'schizotypal signs' (STS) and 'schizophrenia nuclear symptoms' (SNS) and analysed associations with voxel- and surfaced-based brain structural parameters derived from structural magnetic resonance imaging at 3 T with CAT12. For SNS, we found a positive correlation with the volume in the left superior parietal lobule and the precuneus, and a negative correlation with the volume in the right inferior temporal gyrus [p < 0.05 cluster-level Family Wise Error (FWE-corrected]. For STS, we found a negative correlation with the volume of the left and right precentral gyrus (p < 0.05 cluster-level FWE-corrected). Surface-based analyses did not detect any significant clusters with the chosen statistical threshold of p < 0.05. However, in exploratory analyses (p < 0.001, uncorrected), we found a positive correlation of SNS with gyrification in the left insula and rostral middle frontal gyrus and of STS with the left precuneus and insula, as well as a negative correlation of STS with gyrification in the left temporal pole. Our results show that brain structures in areas implicated in schizophrenia are also related to PLE and its associated distress in healthy individuals. This pattern supports a dimensional model of the neural correlates of symptoms of the psychotic spectrum.

Caffeine and Stress Promote a More Liberal Bias on Tasks Assessing Hallucination-Like Experiences and False Memory in a Nonclinical Sample

Psychosis is often thought of as existing on a continuum with clinically diagnosed patients representing the pathological extreme. Subclinical psychosis-like experiences and schizotypal signs, including persecutory beliefs and hallucinations, are not uncommon in the general population. Both stress and levels of caffeine consumption have been demonstrated to exacerbate psychotic phenomena. In this study, reported caffeine consumption, perceived stress, and predisposition to hallucinate were measured in 129 healthy volunteers. The White Christmas Task (WCT) and the Deese–Roediger–McDermott (DRM) paradigm were used as measures of false perception and memory. Reported caffeine consumption was found to be a predictor of liberal bias on the WCT, and stress was found to be a predictor of liberal bias and reduced discriminability on the DRM. Finally, participants high on schizotypy were found to be insensitive to emotional valence on the DRM. It was theorized that these findings may be due to the assignment of undue adaptive importance resulting from elevated dopamine transmission in the striatum.

Impact of childhood adversity on the onset and course of subclinical psychosis symptoms — Results from a 30-year prospective community study

The study objective was to examine childhood adversity in association with intra-individual changes and inter-individual differences in subclinical psychosis in a representative community cohort over a 30-year period of observation.We analyzed two psychosis syndromes derived from the SCL-90-R – schizotypal signs and schizophrenia nuclear symptoms – in 335 participants. Participants were repeatedly assessed between 1978 (around age 20) and 2008 (around age 50). We focused specifically on inter-individual differences and intra-individual changes over time by applying structural equation modeling, generalized linear models, and generalized estimating equations.Several weak inter-individual differences revealed that increased schizotypal signs are related to various childhood adversities, such as being repeatedly involved in fights and parents having severe conflicts among themselves. We also found a significant positive association between schizotypal signs and the total number of adversities a subject experienced. This pointed toward a modest dose–response relationship. The intra-individual change in schizotypal signs over time was rather weak, although some adjustment did occur. In contrast, inter-individual schizophrenia nuclear symptoms were mainly unrelated to childhood adversity. However, some striking intra-individual changes in distress were noted over time, especially those linked with severe punishment and the total adversity score.In conclusion, we have confirmed previous positive findings about the association between childhood adversity and subsequent subclinical psychosis symptoms: An increase in adversity is weakly related to an increase of the psychosis symptom load. However, depending on the kind of adversity experienced the psychosis symptom load decreases gradually in adult life.

Subclinical psychosis syndromes in the general population: results from a large-scale epidemiological survey among residents of the canton of Zurich, Switzerland.

Aims. Prevalence and covariates of subclinical psychosis have gained increased interest in the context of early identification and treatment of persons at risk for psychosis. Methods. We analysed 9829 adults representative of the general population within the canton of Zurich, Switzerland. Two psychosis syndromes, derived from the SCL-90-R, were applied: 'schizotypal signs' and 'schizophrenia nuclear symptoms'. Results. Only a few subjects (13.2%) reported no schizotypal signs. While 33.2% of subjects indicated mild signs, only a small proportion (3.7%) reported severe signs. A very common outcome was no 'schizophrenia nuclear symptoms' (70.6%). Although 13.5% of the participants reported mild symptoms, severe nuclear symptoms were very rare (0.5%). Because these two syndromes were only moderately correlated (r=0.43), we were able to establish sufficiently distinct symptom clusters. Schizotypal signs were more closely connected to distress than was schizophrenia nuclear symptoms, even though their distribution types were similar. Both syndromes were associated with several covariates, such as alcohol and tobacco use, being unmarried, low education level, psychopathological distress and low subjective well-being. Conclusions. Subclinical psychosis symptoms are quite frequent in the general population but, for the most part, are not very pronounced. In particular, our data support the notion of a continuous Wald distribution of psychotic symptoms in the general population. Our findings have enabled us to confirm the usefulness of these syndromes as previously assessed in other independent community samples. Both can appropriately be associated with well-known risk factors of schizophrenia.

Deconstructing sub-clinical psychosis into latent-state and trait variables over a 30-year time span

BackgroundOur aim was to deconstruct the variance underlying the expression of sub-clinical psychosis symptoms into portions associated with latent time-dependent states and time-invariant traits. MethodsWe analyzed data of 335 subjects from the general population of Zurich, Switzerland, who had been repeatedly measured between 1979 (age 20/21) and 2008 (age 49/50). We applied two measures of sub-clinical psychosis derived from the SCL-90-R, namely schizotypal signs (STS) and schizophrenia nuclear symptoms (SNS). Variance was decomposed with latent state–trait analysis and associations with covariates were examined with generalized linear models. ResultsAt ages 19/20 and 49/50, the latent states underlying STS accounted for 48% and 51% of variance, whereas for SNS those estimates were 62% and 50%. Between those age classes, however, expression of sub-clinical psychosis was strongly associated with stable traits (75% and 89% of total variance in STS and SNS, respectively, at age 27/28). Latent states underlying variance in STS and SNS were particularly related to partnership problems over almost the entire observation period. STS was additionally related to employment problems, whereas drug-use was a strong predictor of states underlying both syndromes at age 19/20. The latent trait underlying expression of STS and SNS was particularly related to low sense of mastery and self-esteem and to high depressiveness. ConclusionsAlthough most psychosis symptoms are transient and episodic in nature, the variability in their expression is predominantly caused by stable traits. Those time-invariant and rather consistent effects are particularly influential around age 30, whereas the occasion-specific states appear to be particularly influential at ages 20 and 50.

Negative correlation between leftward bias in line bisection and schizotypal features in healthy subjects

Introduction: Recent studies have found a lack of normal pseudoneglect in schizophrenia patients and in their first degree relatives. Similarly, several contributions have reported that measures of schizotypy in the healthy population may be related to signs of right-sided lateralization, but most of these studies differ greatly in methodology (sample size, choice of schizotypy scales, and laterality tasks) and, consequently, the results cannot be compared and so definitive conclusion cannot be drawn. In this study, our purpose is to investigate whether some tasks of spatial attention may be related to different dimensions of schizotypy not only in a larger sample of healthy subjects (HS), but testing the same people with several supposedly related measures several times.Materials and Methods: In the first part of the study (Part I), the performance on “paper and pencil” line bisection (LB) tasks in 205 HS was investigated. Each task was repeated three times. In the second part of the study (Part II), a subgroup of 80 subjects performed a computerized version of the LB test and of the mental number line bisection (MNL) test. In both parts of the study, every subject completed the 74-item version of the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI).Results: In both parts of the study, high scores on the subscale “magical thinking” of SPQ have resulted in being closely linked to a decreased pseudoneglect as assessed by the LB task. On the contrary, right handedness is related to an increased leftward bias at the same task. No association was found between MNL and the other variables.Discussion: The main finding of this study is that a decreased spatial leftward bias at the LB task correlates with positive schizotypy in the healthy population. This finding supports the hypothesis that a deviation from leftward hemispatial visual preference may be related to the degree of psychosis-like schizotypal signs in non-clinical population and should be investigated as a possible marker of psychosis.

Sex differences in sub-clinical psychosis—Results from a community study over 30 years

Sex differences in schizophrenia have long been reported. They are found within almost all aspects of the disease, from incidence and prevalence, age of onset, symptomatology, and course to its psycho-social outcome. Many sex-related hypotheses have been developed about the biology, psychology, or sociology of that disease. A further approach to study sex differences would be to examine such differences in sub-clinical psychotic states as well. If factors related to full-blown psychosis were equally meaningful over the entire psychosis continuum, we should expect that “true” sex differences could also be identified in sub-clinical psychosis. Here, we studied sex differences in sub-clinical psychosis within a community cohort in Zurich, Switzerland. This population was followed for over 30years and included males and females between the ages of 20/21 and 49/50. We applied two different measures of sub-clinical psychosis representing schizotypal signs and schizophrenia nuclear symptoms. Using cross-sectional and longitudinal analyses, we found no significant sex differences in sub-clinical psychosis over time with respect to age of onset, symptomatology, course, or psycho-social outcome. Thus it appears that sex differences in psychosis manifest themselves at the high end of the continuum (full-blown schizophrenia) rather than within the sub-threshold range. Possibly males and females have separate thresholds for certain symptoms because they are differently vulnerable or exposed to various risk factors.

Linking substance use with symptoms of subclinical psychosis in a community cohort over 30 years

The aim of the study was to examine the temporal associations between substance use and subclinical psychosis symptoms. Data from a prospective community study sampled within a single cohort over 30 years (1978-2008) were analysed with discrete-time hazard models. General population-based sample. At initial sampling in 1978 males (n = 292) were 19 and females (n = 299) were 20 years old. Two psychosis syndromes representing 'schizotypal signs' and 'schizophrenia nuclear symptoms' and various substance use variables including cannabis, alcohol, tobacco and multiple-drug use (i.e. cannabis combined with other drugs). In bivariate analyses, schizotypal signs were predominantly associated with regular cannabis use in adolescence (OR = 2.29, 95% CI 1.32-3.97). Schizophrenia nuclear symptoms were mainly related to alcohol (OR = 1.84, 95% CI 1.00-3.38) and multiple-drug use (OR = 2.35, 95% CI 1.38-4.02) during adolescence. Multivariate analyses showed that, in particular, regular cannabis use during adolescence was associated with the occurrence of subsequent schizotypal symptoms over a 30-year period (OR = 2.60, 95% CI; 1.59-4.23), whereas multiple-drug use in adolescence was associated predominantly with schizophrenia nuclear symptoms (OR = 1.75, 95% CI 1.01-3.03). Alcohol misuse was only slightly associated with the onset of such symptoms. A significant portion of the occurrence of subclinical psychosis symptoms in adulthood can be attributed to excessive cannabis and multiple-drug use during adolescence. This is in line with the hypothesis that long-term sensitization of dopaminergic brain receptors plays a role in developing psychotic symptoms.

Sub-clinical psychosis symptoms in young adults are risk factors for subsequent common mental disorders

Background Not all persons identified in the early stages to be at risk for psychosis eventually cross the threshold for a psychotic illness. However, sub-clinical symptoms may not only indicate a specific risk but also suggest a more general, underlying psychopathology that predisposes one to various common mental disorders. Methods Analyzing data from the prospective Zurich Cohort Study, we used two psychosis subscales – “schizotypal signs” and “schizophrenia nuclear symptoms” – derived from the SCL-90-R checklist that measured sub-clinical psychosis symptoms in 1979. We also assessed 10 different diagnoses of common mental disorders through seven interview waves between 1979 and 2008. This 30-year span, covering participant ages of 19/20 to 49/50, encompasses the period of highest risk for the occurrence of such disorders. Results Both psychosis scales from 1979, but especially “schizotypal signs”, were significantly correlated with most mental disorders over the subsequent test period. Higher values on both subscales were associated with an increasing number of co-occurring disorders. Conclusions Our data demonstrate that sub-clinical psychosis generally represents a risk factor for the development of common mental disorders and a liability for co-occurring disorders. This refers in particular to dysthymia, bipolar disorder, social phobia, and obsessive–compulsive disorder. Proneness to psychosis could signal a fundamental tendency toward common mental disorders.

Risk factors at the low end of the psychosis continuum: Much the same as at the upper end?

We investigated risk factors for subclinical symptoms of psychosis, and focused on two psychosis dimensions previously identified in the Zurich Study, namely “schizophrenia nuclear symptoms” and “schizotypal signs”. We examined the data from 9814 Swiss conscripts from 2003. The psychosis symptom dimensions were derived from the Symptom-Checklist-90-R (SCL-90-R), and were regressed on a broad range of known risk factors for psychosis. Risk factors typically assigned to schizophrenia and other psychotic disorders – cannabis use, childhood adversity, reading and writing difficulties, attention deficit hyperactivity disorder (ADHD), psychiatric disorders and addiction in parents and the extended family – are relevant also at subclinical levels. Our analyses suggested that specific risk factors may be assigned to distinct psychosis dimensions, as previously determined in an analysis from the Zurich Study. If there are different pathways to psychosis characterized by specific symptom dimensions and risk factors, they mostly co-exist and interact at different symptom load levels.

Prevalence and risk factors of psychotic symptoms: in the city of Izmir, Turkey

Psychotic symptoms, psychotic-like experiences and schizotypal signs can emerge in different socio-cultural circumstances and cause clinical or non-clinical pictures. Transient or self-limiting psychotic-like experiences are more prevalent than clinical psychotic disorders. The aim of this study is to determine the prevalence and sociodemographic correlates of psychotic symptoms in an urban area. A cross-sectional study was conducted among the residents of two districts in the urban area of Izmir, Turkey. Among the systematically selected 1,500 residents of 85,212-study population, a total of 1,268 individuals (response rate: 84.5%) were screened for any lifetime psychotic symptoms. Composite International Diagnostic Interview (CIDI) was used to assess psychotic symptoms. CIDI (+) psychotic symptoms were found in 3.6% of the screened sample. Logistic regression analysis showed that being a female (OR=2.4, 95% CI=1.2-5.1), having a first degree family history of any mental disorders (OR=13.9, 95% CI=5.7-34.3), lack of social support (OR=4.5, 95% CI=2.3-8.6) and alcohol use (OR=4.9, 95% CI=2.3-10.6) were all related to psychotic symptoms. Prevalence of any psychotic symptom is lower compared to European studies. Alcohol might be considered as a risk factor for developing psychotic symptoms in the Turkish cultural setting.

Attachment dimensions and schizotypy in a non-clinical sample

Attachment has been proposed to relate to adult psychopathology, although strong evidence for this relation has not been documented. This study investigated peer attachment and parental bonding in relation to schizotypy in healthy adults ( N = 154). Paranoia was the only positive schizotypal sign found to relate to peer attachment, being predicted by attachment anxiety, but not avoidance. Negative schizotypal signs were predicted by levels of both attachment anxiety and avoidance. In addition, paranoia and negative schizotypal traits were predicted by perceived parental care. Implications for theories of schizotypy and future research are discussed.

Psychotic experiences in the general population: A twenty-year prospective community study

Purpose Recent work suggested that psychosis might be expressed at subclinical levels. However, the determinants of subclinical psychotic symptoms, the degree of continuity over the life span, and the impact on functioning remain unclear. Thus we analyzed the prevalence, determinants, patterns and impact of subclinical psychotic symptoms in a community cohort over a 20-year period. Methods The Zurich Study – a longitudinal community study – started in 1979 with a sample of 591 participants aged 20/21 years. Follow-up interviews were conducted at age 23, 28, 30, 35 and 41. Symptoms were assessed with a semi-structured interview and the SCL90-R. In this analysis, items of the SCL90-R symptom dimensions “paranoid ideation” and “psychoticism” were examined. Results Two distinct symptom dimensions of subclinical psychosis became evident, one representing schizophrenia nuclear symptoms, the other representing schizotypal signs. Cannabis use in adolescence was associated specifically with schizophrenia nuclear symptoms, whereas childhood adversity as well as chronic physical or mental disorders in parents contributed to schizotypal signs. Individuals with a persistently high level of either of the two identified symptom dimensions over 20 years experienced significant deficiencies in social achievement and functioning. Conclusions Expression of psychotic symptoms in populations is continuous and characterized by differing levels of severity and persistence. A small group of individuals displays persistence of subclinical psychotic symptoms over a period of 20 years. The causes of and pathways to clinical psychotic disorder can be studied long before the disorder becomes clinically relevant.

Emotional processing in a non-clinical psychosis-prone sample

Symptoms of psychosis have been proposed to form part of a continuous distribution of experiences in the general population rather than being an all-or-nothing phenomenon. Indeed, schizotypal signs have been reported in subjects from non-clinical samples. Emotional processing has been documented to be deficient in schizophrenia. In the present study, we tested the hypothesis whether putatively psychosis-prone subjects would show abnormalities in emotion processing. Based on the extremes of Launay–Slade Hallucination Scale (LSHS) ratings of 200 undergraduate students, two groups of subjects (total N=40) were selected. All 40 participants filled in the Schizotypal Personality Questionnaire (SPQ). We compared both groups on an alexithymia questionnaire and on four behavioral emotional information processing tasks. Hallucination-proneness was associated with an increased subjective emotional arousal and fantasy-proneness. Although no differences between the high and low group were observed on three behavioral emotion processing tasks, on the affective word-priming task presentation of emotional stimuli was associated with longer reactions times to neutral words in high schizotypal subjects. Also, SPQ scores correlated with several emotion processing tasks. We conclude that these findings lend partial support to the hypothesis of continuity between symptoms characteristic of schizophrenia and psychosis-related phenomena in the normal population.

Developmental changes in cortisol secretion in normal and at-risk youth.

Adolescence is associated with an increase in the rate of certain psychiatric symptoms, and it is typically the developmental period when prodromal features of the major psychiatric disorders emerge. This is especially true of schizophrenia, with the majority of patients showing a marked postpubertal rise in schizotypal signs that predates the onset of clinical symptoms in early adulthood. Cross-sectional studies of youth have revealed a positive correlation between age and saliva cortisol level, suggesting a normative maturational increase in activity of the hypothalamic-pituitary-adrenal (HPA) axis. It has been hypothesized that this increase may trigger the expression of symptoms in vulnerable individuals. The present longitudinal study measured cortisol secretion and its relation with symptom development in samples of youth with schizotypal personality disorder (SPD), other personality disorders, or no Axis II disorder. The findings indicate moderate stability in cortisol levels across a 2-year period, with a longitudinal increase in cortisol levels over time. Cortisol levels at the first and second assessments were correlated with the severity of SPD symptoms at follow-up. The results are consistent with the notion that the HPA axis undergoes a postpubertal maturational process that moderates the expression of psychiatric symptoms.

Creativity in Offspring of Schizophrenic and Control Parents: An Adoption Study

Previous studies (Heston & Denney, 1968; Karlsson, 1970; Kauffman, Grunebaum, Cohler, & Gamer, 1979) have reported that psychologically healthier biological relatives of persons with schizophrenia had unusually creative jobs and hobbies. These studies, however, examined only eminent levels of creativity in a few professions, involved serendipitous post hoc findings, assessed creativity, or both, while aware of diagnosis. We studied 36 index adult adoptees of biological parents with schizophrenia and 36 demographically matched control adoptees with no biological family history of psychiatric hospitalization. Adoptees were diagnosed with the Diagnostic and Statistical Manual of Mental Disorders (3rd ed.; American Psychiatric Association, 1980) criteria by investigators blind to creativity assessments. Adoptees' real-life creativity was rated by other investigators blind to personal and family psychopathology with scales of demonstrated reliability and validity applied to descriptions of vocational and avocational activities obtained from interviews. It was hypothesized that adoptees with genetic liability for schizophrenia (and thus potentially unconventional modes of thinking and perceiving)-although not schizophrenia itself-would be more creative. In fact, nonschizophrenics with either schizotypal or schizoid personality disorder or multiple schizotypal signs (which other research has linked with genetic liability for schizophrenia) had significantly higher creativity than other participants. Interestingly, some control adoptees also fit these criteria and were included in analyses. Results have implications for relations of creativity to personal symptoms and familial risk for schizophrenia.

The reliability of the structured interview for schizotypy-revised.

We investigated the reliability of the Structured Interview for Schizotypy-Revised (SIS-R). The original interview (SIS) was developed by Kendler. We revised the SIS, primarily by standardizing the rating procedures. Operational definitions and explicit criteria for rating were given. We introduced a four-point scale and provided clear criteria for rating severity of symptoms and signs (frequency, duration, and level of conviction) to operationalize schizotypal features. We divided schizotypal signs of global affect and global organization of speech into three separate signs of affect and five separate signs of thinking and speech. The main goal of this study was the assessment of test-retest reliability of the SIS-R. A robust test-retest design using different interviewers at both times, with a mean interval of 19 days, was used. The sample consisted of 42 psychiatric patients, almost all with personality disorders. The strong linear-weighted kappa statistic was used to evaluate reliability. The first conclusion is that most schizotypal symptoms can be reliably assessed with the SIS-R. The second conclusion is that most schizotypal signs do not reach sufficient levels of reliability. After unreliable items are excluded, the shortened SIS-R is a reliable research instrument for measuring schizotypal features (as far as it concerns our mixed samples). It covers all three dimensions of schizotypy.

Nightmares and Schizotypy

In order to explore the proposed relationship between nightmare occurrence and schizotypy, 30 frequent-nightmare subjects (at least one occurrence per week) and 30 low-nightmare controls, all of whom were female college students, were compared on several converging measures of schizotypal signs and behaviors. Consistent with previous research, frequent nightmare subjects demonstrated greater deviance on psychometric scales of schizotypy, and reported significantly greater schizotypal symptomatology on a structured clinical interview, than controls did. In addition, nightmare subjects produced similar electrodermal habituation patterns to auditory orienting stimuli as those that have been documented in schizophrenia-spectrum disorders. The results suggest that nightmare experience may be a useful conjoint behavioral indicator for the early detection of schizophrenia-spectrum psychopathology.

Schizotypal symptoms and signs in the Roscommon Family Study. Their factor structure and familial relationship with psychotic and affective disorders.

Although schizotypal personality disorder aggregates in relatives of schizophrenic probands, the criteria for this disorder may not be optimal either in describing the dimensions of schizotypal phenomena or in identifying those with a high familial liability to schizophrenia. In the Roscommon Family Study, an epidemiologically based family study of major psychiatric disorders conducted in the west of Ireland, we examined 25 individual schizotypal symptoms and signs, assessed by structured personal interview, in 1544 first-degree relatives (without chronic psychosis or mental retardation) of five proband groups: schizophrenia; other nonaffective psychoses; psychotic affective illness; nonpsychotic affective illness; and matched, unscreened controls. We obtained seven meaningful schizotypal factors: negative schizotypy, positive schizotypy, borderline symptoms, social dysfunction, avoidant symptoms, odd speech, and suspicious behavior. Taken individually, all of these factors, except borderline symptoms, significantly discriminated relatives of schizophrenic probands from relatives of controls; in descending order of the odds ratios, they were odd speech, social dysfunction, suspicious behavior, negative schizotypy, avoidant symptoms, and positive schizotypy. In a multivariate analysis, four of these factors remained significant: odd speech, negative symptoms, social dysfunction, and avoidant symptoms. These schizotypal factors differed in their specificity. Three of the four most predictive schizotypal factors also significantly discriminated relatives of probands with other nonaffective psychoses from relatives of controls. "Schizotypy" is a complex, multidimensional clinical construct, whose various dimensions differ widely both in the degree and specificity with which they reflect the familial liability to schizophrenia. Subpsychotic thought disorder; negative schizotypal signs, such as poor rapport and odd behavior; deficient occupational functioning; and social isolation/avoidance best characterized relatives of schizophrenic probands compared with relatives of matched controls.

The Structured Interview for Schizotypy (SIS): a preliminary report.

This article presents a new interview-based research instrument for assessing schizotypal symptoms and signs. The Structured Interview for Schizotypy (SIS), which was developed from experience gained in a large, controlled family study of schizophrenia in the west of Ireland and has been field-tested in three other locations, differs from previously available interviews in that it includes: (1) built-in contextual assessments of the pathological nature of certain symptoms (e.g., suspiciousness or ideas of reference); (2) multiple independently scored items, most with closed response options, per symptom scale; (3) extensive assessment of schizotypal signs; (4) symptom probes designed to make responding positively appear nondeviant; and (5) coverage of potentially relevant symptoms and signs not required in current criteria for schizotypal personality disorder. Schizotypal symptoms can be assessed with high reliability by the SIS. When sufficient variability is present, schizotypal signs are also reliably assessed by the SIS, although the reliability is generally lower than that found for symptoms. In three independent pilot studies, schizotypal symptoms and signs assessed by the SIS appear to discriminate significantly the relatives of schizophrenic patients from relatives of controls.