Positive and negative schizotypy in a student sample: neurocognitive and clinical correlates

Abstract

Positive and negative schizotypy may represent discrete factors or dimensions. To determine if distinct neurocognitive profiles are associated with these dimensions or factors, we classified university students on the basis of positive and negative schizotypal symptoms and conducted separate analyses. Following prior work in the neuropsychiatric literature, we predicted that subtle prefrontal deficits would be selectively associated with negative schizotypal personality features in a nonclinical student sample. We also investigated the relationship between positive/negative schizotypy and associated clinical states or personality dimensions including antisocial personality disorder, obsessive–compulsive personality traits, generalized and social anxiety, empathy, and impulsivity. Classification of subjects into positive and negative schizotypy groups revealed distinct neurocognitive and clinical profiles. We observed a positive relation between measures of temporolimbic dysfunction, impulsivity, antisocial behavior, and positive schizotypal phenomena. Negative schizotypy was associated with subtle performance deficits on measures of frontal executive function, increased social anxiety, and obsessive–compulsive phenomena. Findings are consistent with the contention that positive and negative schizotypy represent discrete factors.

Introduction

Schizotypal personality disorder (SPD) has been conceptualized as an attenuated form or phenotypic variant of schizophrenia. Diagnostic criteria for SPD include ideas of reference, magical ideation, unusual perceptual experiences, odd thinking and speech, suspiciousness, inappropriate or constricted affect, eccentric behavior, lack of close friends, and excessive social anxiety (American Psychiatric Association, 1994).

Subtle prefrontal deficits are associated with schizotypal personality. Individuals receiving a SPD diagnosis demonstrate a greater degree of impairment on tests assessing frontal executive function including the Wisconsin Card Sorting Test (Diforio et al., 2000, Trestman et al., 1995, Voglmaier et al., 1997), California Verbal Learning Test (Bergman et al., 1998, Voglmaier et al., 1997), and the Trail-Making Test (Trestman et al., 1995). Schizotypic subjects also exhibit performance deficits on visuospatial working memory tasks (Farmer et al., 2000, Park and McTigue, 1997, Roitman et al., 2000). Moreover, schizotypic subjects manifest volumetric abnormalities (i.e. volume reduction) in temporal and prefrontal regions (Dickey et al., 1999, Buchsbaum et al., 1997, Raine et al., 1992a).

University students psychometrically defined as schizotypic or ‘psychosis-prone’ also exhibit performance deficits on tasks assessing frontal executive function including the Wisconsin Card Sorting Test (Lenzenweger and Korfine, 1994, Lyons et al., 1991, Poreh et al., 1995, Suhr, 1997), Trail-Making Test (Poreh et al., 1995), and the Booklet Category Test (Poreh et al., 1995).

Schizotypy is not invariably associated with impaired performance on tasks assessing frontal executive function. Lenzenweger and Gold (2000) found that students psychometrically identified as schizotypic did not demonstrate performance deficits on verbal and auditory working memory tasks in comparison to controls. How can we account for these conflicting results?

One possibility is that students psychometrically defined as schizotypic present with a less severe form of schizotypal personality relative to subjects diagnosed with SPD. However, several studies found that subjects diagnosed with SPD did not demonstrate performance deficits on tests assessing frontal executive functioning (i.e. the WCST) (Raine et al., 1992b, Condray and Steinhauer, 1992).

A second possibility is that neurocognitive deficits are selectively associated with negative, rather than positive, symptoms. A discussion of the two-factor model (or two-syndrome construct) of schizotypy may clarify this issue. A two-factor model of schizotypy is based on Crow's two-syndrome concept of schizophrenia (i.e. Type I — positive symptoms and Type II — negative symptoms) (Crow, 1980, Crow, 1985). Variations in dopaminergic activity are associated with both positive and negative schizotypy (Siever, 1995). Hypodopaminergia in prefrontal cortex is associated with negative symptoms such as affective flattening, avolition and apathy, asociality, and cognitive impairment. Hyperdopaminergia in subcortical mesolimbic structures may generate positive schizotypal symptoms including magical ideation, ideas of reference, and unusual perceptual experiences. Several researchers suggest that positive and negative schizotypy represent distinct factors or dimensions. Siever (1995) noted that these dimensions or factors are independently heritable and speculated that distinct pathophysiologies underlie each dimension.

To determine if distinct neurocognitive profiles are associated with these factors, we classified subjects on the basis of positive and negative schizotypal symptoms and conducted separate analyses of neurocognitive test performance.

Negative schizotypy may be selectively associated with executive dysfunction. Diforio et al. (2000) reported that adolescents with SPD demonstrated performance deficits on the modified WCST. Moreover, impaired performance on the WCST was associated with negative, rather than positive, symptoms. As noted previously, Lenzenweger and Gold (2000) found that students psychometrically identified as schizotypic did not exhibit performance deficits on working memory tasks relative to controls. It is important to note that Lenzenweger and Gold employed the Perceptual Aberration Scale to classify subjects. The Perceptual Aberration Scale taps positive schizotypal symptoms (e.g. perceptual distortions). However, Lyons et al. (1991) recruited schizotypal subjects via newspaper advertisements which highlighted positive symptoms (i.e. advertisements seeking individuals who had experienced paranormal phenomena such as ESP and telepathy) and found that individuals with positive symptom schizotypy demonstrated performance decrements on the WCST relative to control subjects.

The present study uses a student sample to investigate whether subtle prefrontal deficits are selectively associated with negative schizotypal personality features. Following prior work in the neuropsychiatric literature, we predicted that negative schizotypy would be associated with impaired performance on tests assessing frontal executive function.

We also investigated the relationship between positive/negative schizotypy and associated clinical states or personality dimensions including antisocial personality disorder (APD), obsessive–compulsive personality traits, generalized and social anxiety, empathy, and impulsivity. In prior work, we observed an association between schizotypal personality features, obsessive–compulsive personality traits, and excessive social anxiety. Are these clinical states selectively associated with positive or negative schizotypy?

Meehl (1989) suggested that a significant subset of psychopathic subjects are schizotaxic. Siever et al. (1990) found that approximately 20% of SPD patients also met diagnostic criteria for APD. We predicted that individuals psychometrically defined as schizotypic would achieve significantly higher scores on a measure of antisocial personality relative to comparison subjects. Although schizotypy may be associated with antisocial personality, it has not been determined whether antisocial behavior is selectively associated with positive or negative schizotypal personality features and we make no a priori predictions.

In prior unpublished work, we observed an association between measures of impulsivity, empathy, and schizotypal personality. We found that subjects psychometrically defined as schizotypic obtained significantly higher scores on measures of impulsivity and significantly lower scores on measures of empathy relative to matched controls. In the present study, we included self-report measures of impulsivity and empathy.

In prior work, we observed an association between schizotypal personality features and obsessive–compulsive personality traits (OCPTs). Moreover, both OCPTs and schizotypal personality features were associated with performance deficits on tests assessing frontal executive function (Aycicegi et al., 2001, Dinn et al., 2001a, Dinn et al., 2001b). We suggested that the preoccupation with rules and organization, perfectionism, and inflexibility displayed by subjects exhibiting OCPTs may represent behavioral strategies which evolve in response to executive function deficits.

Why would OCPD and schizotypal personality covary? As noted previously, negative symptoms are associated with cognitive deficits (i.e. performance deficits on tests of frontal executive functioning). OCPTs may represent adaptive or compensatory strategies which develop in response to executive function deficits. That is, OC symptoms may represent adaptations to subtle prefrontal deficits associated with negative schizotypy. In the present study, we predict that students obtaining high scores on a measure of negative schizotypal symptoms will also achieve clinically significant scores on a measure of obsessive–compulsive personality.

However, in prior work, we also observed a strong relation between social anxiety and obsessive–compulsive phenomena. Thus, OC symptoms, such as compulsive rituals and checking behaviors, may represent compensatory mechanisms for reducing anxiety. Given that both OCD and SPD are associated with social anxiety, it is important to understand the relation between schizotypy and anxiety states, and separately examine social vs. generalized anxiety. Indeed, excessive social anxiety is a characteristic clinical feature of SPD (American Psychiatric Association, 1994).

Our principal research objectives were:

• an exploration of the relationship between positive and negative schizotypy, and neuropsychological test performance in a student sample;

• an investigation of the relation between schizotypy and associated clinical states or personality dimensions including antisocial behavior, obsessive–compulsive phenomena, generalized and social anxiety, empathy, and impulsivity.