Introduction

Emotional impairments have been considered to be core features of schizophrenia [1], [2]. These impairments include both the reduced ability to experience pleasure (e.g., anhedonia) and to express emotion (e.g. affect) [3], [4], [5], [6]. However, most recent findings suggest that patients with schizophrenia often show a relatively intact ability to experience pleasure in response to positive laboratory stimuli [7], [8] regardless the impairment of hedonic capacity generated from clinical observations and self-reports studies [5], [6]. Empirical findings also suggest that ambivalent experiences of pleasure in schizophrenia may result from cognitive and motivational impairments [9], [10], [11], [12].

Deficits in the ability to experience pleasure in schizophrenia may also be divided into anticipatory (feeling of wanting) and consummatory (feeling of liking) dimensions [13]. Based on this framework, individuals with schizophrenia have been shown with intact consummatory pleasure but impaired anticipatory pleasure [13], [14], [15]. However, most of these studies were limited to patients with schizophrenia. Recent empirical findings from at-risk individuals for psychosis such as schizotypal personality disorder (SPD) traits or schizotypy [16], [17], [18], [19] also suggest that deficits in hedonic capacity may even be manifested in a subtle dysfunction even before the development of full-blown psychosis [20], [21], [22].

Studies of emotional processing often emphasize negative or positive aspects of SPD. Individuals with negative SPD (which is similar conceptually to negative schizophrenia symptoms), for example, often attend less than controls to their emotional states, while individuals with positive SPD (which is similar conceptually to positive schizophrenia symptoms), often attend more than controls to their emotional states [23]. Furthermore, depression and anxiety seem to be associated with more positive SPD than negative SPD [24], [25]. However, very little is known about the experience of pleasure and emotional expression in individuals with SPD.

Therefore, despite that a relatively substantial work on anhedonia has been done on schizophrenia spectrum disorders, most of them were limited to individuals who have developed a full-blown psychosis. Very little is known whether anhedonia has been demonstrated at-risk individuals with SPD features. The current study attempts to bridge the gap by exploring the experience of pleasure and emotional expression in individuals with SPD features. Given the heterogeneity of SPD, cluster analysis was used to identify different SPD subtypes. Cluster analysis is an empirical method used to group individuals based on their similarities/differences on selected variables, so that within-group differences are minimized and between-group differences are maximized [26], [27]. Previous studies have supported the existence of “negative SPD” and “positive SPD” clusters in non-clinical college students [28], [29].

We hypothesize that clusters of negative and positive SPD will be identified in a sample of college students who show elevated levels of SPD. We hypothesize further that individuals in the negative SPD cluster will show deficits in anticipatory pleasure, but will demonstrate intact consummatory pleasure and reduced emotional expressivity. By contrast, we expect that individuals with positive SPD will show a lesser extent of impairments as compared to the negative SPD in anticipatory and consummatory pleasure, and intact emotional expression.

Methods

Participants and procedure

Participants were screened out from a sample of 1039 college students aged 16–23 years old in four universities in Beijing, according to their scores on the Schizotypal Personality Questionnaire (SPQ) [30]. Subjects who scored in the top 10th percentile (SPQ score≥36) and the bottom 10th percentile (SPQ score≤10) of the screening sample served as the SPD and the comparison control groups, respectively. Consequently, 117 SPD (mean age = 18.44 years, standard deviation (SD = 0.83) and 116 control (mean age = 18.56 years, SD = 0.79) subjects were enrolled in the study. The groups did not differ significantly in age, years of education or gender (see Table 1).

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Table 1. Characteristics of participants.

https://doi.org/10.1371/journal.pone.0034147.t001

Results

Cluster analysis

Ward's hierarchical cluster analysis confirmed a two-cluster solution in the SPD group. Subsequent K-means cluster analysis further refined the clustering solution. The solution demonstrated one subgroup with prominent interpersonal difficulties that best corresponded to negative SPD, and a second group with prominent cognitive-perceptual problems that best corresponded to positive SPD. The two SPD groups and the comparison control group did not differ significantly in age, years of education, or gender ratio (see Table 2).

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Table 2. Comparisons among groups.

https://doi.org/10.1371/journal.pone.0034147.t002

Discussion

The current study showed that negative and positive SPD groups differ in their experience of pleasure and in their expression of emotion. Consistent with our hypothesis, the negative SPD group showed impaired anticipatory pleasure but relatively intact consummatory pleasure compared to controls. They also showed the least emotional expression among three groups, and reported the highest levels of problems with memory, depressive symptoms and trait-anxiety. The positive SPD group showed heightened pleasure experiences compared to controls, and similar total emotional expression, which provides partial support for our initial hypothesis. They also reported significantly greater problems with everyday memory, depressive symptoms and trait-anxiety than the control group, but significantly lower levels than the negative SPD group.

Findings of reduced anticipatory pleasure but intact consummatory pleasure in the negative SPD group are consistent with findings obtained in patients with schizophrenia [14]. Based on the view that deficits in anticipatory pleasure are related to deficits in motivation in schizophrenia [14], [15], our results raise the possibility that deficits in anticipatory pleasure may be related to deficits in motivation in negative SPD, too. Deficits in anticipatory pleasure in negative SPD may involve similar mechanisms to those that have been proposed for schizophrenia, such as difficulties in initiating approach behavior or in coupling the subjective experience of pleasure to the initiation or maintenance of goal-directed behaviors [42], [43].

In contrast to negative SPD, some of our findings concerning the experience of pleasure in positive SPD were unexpected. We hypothesized that the positive SPD group would show intact anticipatory and consummatory pleasure, and intact emotional expression. Interestingly, they showed a significantly heightened experience of overall, anticipatory and consummatory pleasure, compared to the control group. This may relate to previous findings of heightened emotionality and excessive attention to emotions in positive SPD [23], [44]. In one undergraduate sample, for example, higher levels of hallucinations (a positive symptom) were related to greater emotional arousal and fantasy-proneness [45].

The two SPD groups demonstrated distinct patterns of emotion expressivity with each other. The negative SPD group expressed the l lowest levels of emotions, while the positive SPD group did not differ from the controls in the total amount of emotional expression. However, after examining the scores of each factor of EES, findings showed that on the factor of expression, the negative SPD group scored lowest among the three groups, while the positive SPD group scored higher than controls. On the factor of suppression, both SPD groups displayed less emotional expressivity than the controls. Studies in SPD also show that during lab-based assessment of emotional processing, patients with schizophrenia demonstrated less emotional expression when watching sequentially-presented positive, neutral, and negative valence emotional stimuli. The decreased emotional expression in schizophrenia may be related to a decreased ability to amplify emotional expression. For example, Henry et al. [46] found that patients with schizophrenia demonstrated difficulty in amplifying their emotional expression behavior but did not show difficulty in suppressing it when they were asked to regulate their emotional expression when they watched amusing film clips. In another study, Henry et al. [47] also showed there was a similar decreased amplification of emotional expression, but not suppression in individuals with SPD. The current findings thus appear to be consistent with previous studies and demonstrate that negative SPD may have significant similarities to emotional expression with schizophrenia.

Findings from high risk groups suggest that high scores on anhedonia (negative feature) are related to high risk for schizophrenia [21], [22], [48] while high scorers on the Perceptual Aberration and Magical Ideation Scales (positive features) are at increased risk for future psychosis [49]. Our findings lend support on this view, although the connection between different high risk subtypes and schizophrenia remains unclear. The issue of whether individuals with prominent negative SPD features are more likely to develop schizophrenia, for example, or show poorer prognoses generally, requires additional research. Similarly, the issue of whether individuals with prominent positive SPD features are more likely to develop psychosis or to show better prognoses generally also requires additional study.

There are several limitations in our study. First, all of our participants were college students. Further study with more representative samples in the general population or in samples with clinically diagnosed SPD are needed to validate the current findings. Second, this study only used a series of self-reported scales to assess emotional processing and other dimensions of clinical and cognitive function. More objective experimental methods testing anticipatory and consummatory aspects of pleasure, emotional expression, and relationships between emotional processing and other relevant variables are needed, such as those involving specific anticipatory and motivational components of emotion experience [42], [50]. Future studies should also examine the underlying neural bases of emotional processing in SPD. Third, therapeutic intervention to SPD subjects would affect on their psychological performances. Although this study was not longitudinally-designed one, it would be possible that the individuals with SPD have been recommended to meet school counselors or psychologists previously. However, we did not officially count for this information. Nevertheless, we attempted to refer the SPD cases to the school counselors of their own colleges in order to take proactive action as much as possible. Last but not least, the current study did not administer a comprehensive battery or scales to either record socio-economic status of the participants or further differentiate subtyping of at-risk individuals such as schizoid personality who would potentially have the tendency of anhedonia. Future study should adopt a more systematic approach to get rid of any other personality subtypes that may confound the findings.

Nevertheless, the current findings demonstrate important differences between non-clinical individuals with negative and positive SPD traits. In particular, individuals with negative SPD showed more emotional and behavioral manifestations similar to patients with schizophrenia, while individuals with positive SPD tended to perform closer to controls in several, though not all, dimensions assessed.