Are Disturbances in Mentalization Ability Similar Between Schizophrenic Patients and Borderline Personality Disorder Patients?

Abstract

There is a growing interest in ToM performance among individuals with psychiatric disorders. However, the difference and the performance level between different diagnoses are unclear. Here, we compared the ToM abilities of schizophrenia (SZ), schizoaffective (SZaff), and borderline personality individuals (BPD) with healthy individuals. Individuals with SZ (n = 44), SZaff (n = 11), BPD (n = 11), and healthy individuals (n = 18) were recruited from Mazor Mental Health Center. All groups underwent the Reading Mind in the Eyes (RME) and the Faux Pas recognition test (FB) to assess TOM ability and completed empathy and autism questionnaires. The current results show that the three diagnostic groups performed worse in the RME and FB test compared to healthy individuals. However, women with BPD performed significantly better in ToM tasks than women with SZ and SZaff. Individuals with schizophrenia and BPD scored higher on the autism spectrum questionnaire, while all the diagnostic groups scored lower on the empathy quotient scale than healthy individuals. Finally, a positive correlation was found between ToM ability and empathy. Strikingly, our findings challenge the ability to use ToM as a differential clinical diagnostic tool, especially among men, and strengthen the correlation between decreased empathy and impaired ToM.

1. Introduction

Schizophrenia is associated with a deficit in social functioning and social cognition. Individuals with schizophrenia exhibit substantial and persistent impairments in identifying emotions, social perceptions, and emotion processing [1,2]. One of the critical components in the functional impairment of social cognition in schizophrenia is the ability to attribute another person’s mental states, such as thoughts, beliefs, and intentions. Unsurprisingly, individuals with schizophrenia performed worse in different tasks that assay the individual ability to evaluate and judge the mental state of another [3,4,5]. Previous studies reported a large magnitude of deficits in understanding that another person has beliefs different from one’s own and in decoding another’s complex mental states [6,7]. Notably, individuals with schizophrenia showed deficits in recognizing social Faux Pas [8], and it was demonstrated that individuals with schizophrenia performed worse in the “Reading the Mind in the Eyes” (eyes) test (a simple, well-defined task to infer the mental state of others) than healthy individuals [9]. These findings suggest that understanding another person’s mental state may serve as a trait marker of the disorder, and is not dependent on the current state of the illness. Impairments in social functioning and cognition in individuals with schizophrenia may stem from abnormal activity in brain regions collectively referred to as the “social brain”, including the prefrontal cortex, orbitofrontal cortex, anterior cingulate cortex, premotor cortex, and inferior parietal cortex [10]. Interestingly, a previous study has shown that schizoaffective individuals might differ in their ability to decode other people’s mental states from people with schizophrenia and first-episode individuals [9]. However, whether schizophrenia and schizoaffective individuals differ in their ability to decode the mental state of others and other social cognitive is still unclear.

Studies examining mentalization have also been conducted among other mental health disorders diagnostic groups [11], including borderline personality disorder (BPD). Borderline personality disorder (BPD) is a debilitating psychiatric condition in about 1–2% of the general population, 6% of primary care patients, and up to 20% of patients in psychiatric hospitals and outpatient clinics. A meta-analysis found that BPD patients underperformed in mental state reasoning and cognitive ToM, but not in decoding the mental state of others [12,13]. On the other hand, a recent study found that PBD patients tend to hypermentalize when they misinterpret social information [14]. However, the similarity and the difference in the level of performance between the different diagnostic groups are less studied. Previous evidence suggests that dysfunction in ToM tasks among individuals with BPD is likely related to impairments in the social brain. These include structural changes in the limbic region, such as the hippocampus and amygdala, as well as a reduction in frontal lobe volume, which may contribute to decreased inhibitory function [14,15].

The relationship between decoding the mental state of others and autistic symptoms was suggested before [16,17]. Notably, it was demonstrated that performance in the eyes test is inversely correlated with performance in the Autism Spectrum Quotient (AQ), a self-report questionnaire that estimates the degree of autistic-related traits in healthy and non-healthy individuals [16,17]. Consequently, a high score on the AQ questionnaire (more autistic traits) is strongly correlated with impaired eye test performance. Indeed, individuals with autism characterized by impaired social and communicative functioning displayed poor performance on the eyes task. Furthermore, an eye test–AQ correlation was found in females, but not males, with autism. On the other hand, an inverse eyes test–AQ correlation was found only in healthy men, but not in women [18]. However, whether this eyes test–AQ correlation occurs in other psychiatric disorders associated with social withdrawal, communication impairment, and social cognition deficit is unknown. Here, we compared the mentalization abilities of patients diagnosed with schizophrenia with and without an affective component, patients with borderline personality disorder (BPD), and healthy individuals, focusing on both the affective and cognitive components of ToM. Additionally, we examined correlations between ToM, autistic traits, and empathy.

2. Materials and Methods

2.1. Subjects

The Mazor Mental Health Center Helsinki committee approved the study, and all participants gave informed consent to participate. Forty-four clinically stable individuals with schizophrenia (SZ), eleven individuals with schizoaffective (SZaff), and eleven individuals with borderline personality disorder (BPD) meeting the DSM-5 criteria were recruited from the open and closed wards of Mazor Mental Health Center, Acre. Inclusion criteria were: (1) males and females 18–60, and (2) sufficient knowledge of the Hebrew language. The exclusion criteria were: (1) drug or alcohol abuse, (2) intellectual disability, and (3) organic brain pathology. Clinical and sociodemographic data were collected from the participant’s electronic medical records and included age, sex, education, ethnicity, age of onset, number of hospitalizations, duration of the illness, and family history. Eighteen healthy individuals without psychiatric history and drug or alcohol abuse served as controls. Sociodemographic information was collected from a self-reported questionnaire, including age, sex, education, and ethnicity.

2.2. Reading the Mind in the Eyes Test

The “Reading the Mind in the Eyes” (eyes test) test was developed by Baron-Cohen [18] as a tool to evaluate the ability to infer the mental state of another person. In this task, participants are presented with 36 still pictures of the eye region of faces illustrating emotionally charged or neutral mental states. They were then asked to choose which of the four words best described what the person in the picture was thinking or feeling. This task is considered an advanced ToM test, since the participants need to imagine themselves in the mind of the person shown in the picture. One limitation of the test is that the participants only decode the relevant mental state without predicting or explaining the other person’s action. The score on the eyes test is calculated as the total number of correctly identified mental states.

2.3. Faux Pas Recognition Test (FP-T)

“Faux Pas” is a term that originated from French, and is used to describe words or behaviors that are not socially acceptable or impolite. The test is based on Gregory et al. [19]. In brief, the test includes 20 short stories in random order: 10 Faux Pas stories, and 10 without Faux Pas motives that served as control. The stories were read out loud, and the subject was asked six questions to identify the “Faux Pas” motif and two-story comprehension questions. For each story containing a Faux Pas, the subject receives 1 point for each question answered correctly. If the subject answer “no” to the first question, “if anyone said something that they should not have said”, they will receive 0 points for that whole story. Sixty points can be scored in the Faux Pas stories test. The subject also scores 2 points if they recognize that the story did not include a Faux Pas motive (20 points can be achieved on the stories without Faux Pas). In addition, the subject receives 1 point for each story comprehension question answered correctly (overall, a total of 40 points). The Z-normalization methodology was used in the current study to obtain comprehensive and integrated performance measures in the Faux Pas recognition test. Briefly, for the Faux Pas stories and the Non-Faux Pas stories, the Z-score for an individual was calculated using the following equation:

$$Z={\displaystyle \frac{\mathrm{X}-\mu }{\sigma }}$$

The Z-score indicates how many standard deviations (SD) an observation (X) is above or below the mean of a control group (µ) from the same sex. X represents the individual data point for the observed parameter. µ and σ represent the control group’s mean and standard deviation. The current study calculated Z-score values for test parameters measuring ToM ability. The directionality of the scores was adjusted so that decreased negative Z-score values reflected a weak ToM ability.

ToM ability Z-score (Z_ToM) was calculated for each subject using normalization of the Faux Pas stories score (FP) and Non-Faux Pas stories (NFB),

$${\mathrm{Z}}_{\mathrm{ToM}}={\displaystyle \frac{FP\left(\frac{\mathrm{X}-\mu }{\sigma }\right)+NFB\left(\frac{\mathrm{X}-\mu }{\sigma }\right)}{Number of parameters}}$$

2.4. The Empathy Quotient Scale (EQ Scale)

EQ scale was used to study the subject’s ability to empathize. This questionnaire is intended to measure how easily the subject notices other people’s feelings, and how strongly the subject is affected by other people’s feelings. It includes 40 questions related to empathy, and 20 control questions. For each of the statements, the subject must choose one of these options: “Totally agree”, “Some agree”, “Some disagree”, or “Do not agree at all”. The average scores on this test are 47 for women and 42 for men [20].

2.5. Autism Spectrum Quotient (AQ)

The questionnaire consists of 50 sentences in random order related to autism traits (social skills, routine, switching, imagination, and numbers/patterns). In brief, participants are asked to indicate whether they “strongly agree”, “slightly agree”, “slightly disagree”, or “strongly disagree” with each statement. A score is calculated by summing across items [21]. Each item scores zero or one. One point is scored if the participant chooses the ’autistic trait’ response.

2.6. Statistical Analysis

Statistical analyses were performed using IBM SPSS statistics version 26 and GraphPad Prism 8.2. Differences between groups were assessed using one-way and two-way ANOVAs. Significant main effects and interactions were further pursued using Post hoc by Tukey’s test and independent sample t-test. The Kruskal–Wallis test was performed for non-parametric tests, followed by the Bonferroni correction test. Pearson correlation coefficient was performed to test correlations between variables. Z-score analysis was used to obtain comprehensive and integrated Faux Pas recognition test performance measures. Data are presented as Mean ± SD or mean rank and Tukey range. The accepted significance value for all tests was set at p < 0.05.

3. Results

3.1. Socio-Demographic and Clinical Characterization

Sixty-six participants were recruited from the open and closed wards of Mazor Mental Health Center for this study, while eighteen healthy individuals served as control. Overall, 62% of the study participants were men. Individuals with schizophrenia without the affective component were significantly older [F_(3,80) = 3.189, p = 0.028] compared to individuals with BPD (Tukey’s, p < 0.05,

Table 1. Demographic and clinical data by group.

	Controls (n = 18)	SZ (n = 44)	SZaff (n = 11)	BPD (n = 11)	p-Value
Age (years)	34.3 ± 2.8	41.2 ± 1.8	41.2 ± 3.4	30.8 ± 3.1	p = 0.028 a
Sex
Men	7 (39%)	36 (82%)	7 (64%)	2 (18%)
Women	11 (61%)	8 (18%)	4 (36%)	9 (82%)
Education (years)	17.1 ± 0.6	12.1 ± 0.3	12.4 ± 0.4	11.2 ± 0.5	p < 0.001 a
Onset (years)		29.4 ± 1.5	28.9 ± 2.8	26.7 ± 3.4	p = 0.73 a
No. of hospitalizations		11.5 ± 1.7	9.4 ± 2.6	6.7 ± 2.5	p = 0.22 b
Years of illness		11.0 ± 1.2	12.5 ± 1.9	4.7 ± 1.3	p = 0.021 a

Note: Data presented as a mean ± standard error of the mean (SEM). ^a One-way ANOVA, ^b Kruskal–Wallis test. Abbreviations: SZ: schizophrenia; SZaff: schizoaffective; BPD: borderline personality disorder.

). In addition, all groups, including schizophrenia patients with and without the affective component and BPD patients, had fewer years of education compared to the control groups [F_(3,80) = 31.032, p < 0.001, Table 1]. No statistical difference in the years of education between BPD and the schizophrenic diagnosis groups was found (Table 1). At the clinical levels, no statistically significant differences were found between the study groups in the mean age of the onset and number of hospitalizations [one-way ANOVA, F_(2,65) = 0.30, p = 0.73; Kruskal–Wallis test, χ²₍₂₎ = 2.987, p = 0.22, N = 66, respectively; Table 1]. However, the duration of the illness was significantly higher in individuals with schizophrenia and schizoaffective disorder than in BPD [F_(2,63) = 4.13, p = 0.021; Tukey’s, p < 0.05, Table 1].

3.2. Reading the Mind in the Eyes Is Impaired in Individuals with Schizophrenia, Schizoaffective Disorder, and BPD

The ability to decode another person’s mental state was evaluated using the eyes test. No statistically significant main effect of sex, or interaction between sex and the diagnosis group, was found [F_(1,76) = 1.50, p = 0.23, η² = 0.019; F_(3,76) = 0.81, p = 0.49, η² = 0.031, respectively]. Therefore, both sexes were analyzed together. The analysis revealed a significant difference in the RME test between groups (Kruskal–Wallis test, χ²₍₃₎ = 22.46, p < 0.001, N = 84; adjusted using the Bonferroni correction, p < 0.001; Figure 1). The difference was driven by significantly worse performance in the RME test in the SZ and the SZaff group compared to the control group. Thus, individuals with schizophrenia and schizoaffective disorder received a lower score, and made more mistakes in describing what the person in the picture was thinking or feeling compared to the healthy individuals (Kruskal–Wallis test, adjusted using the Bonferroni correction, p < 0.001; Figure 1). However, no difference in the ability to decode the mental state of others was noted in the RME performance of the individuals with BPD, compared to SZ, SZaff and healthy individuals (Figure 1).

3.3. Recognition of the Faux Pas Motif Is Impaired in Individuals with Schizophrenia, Schizoaffective Disorder, and BPD

Analysis of the participant’s ability to recognize the Faux Pas motif reveals a significant main effect of diagnosis [F_(3,76) = 33.44, p < 0.001, η² = 0.569], but not sex [F_(1,76) = 1.12, p = 0.29, η² = 0.05], and without interaction between diagnosis and sex factors [F_(3,76) = 2.41, p = 0.07, η² = 0.087]. Therefore, both sex groups were analyzed together. In comparison with the healthy individuals, all three diagnosis groups recognized fewer Faux Pas motif stories (Kruskal–Wallis test, χ²₍₃₎ = 42.43, p < 0.001, N = 84; adjusted using Bonferroni correction, p < 0.001; Figure 2A). There was no significant difference between the three diagnosis groups (Bonferroni correction, p > 0.05; Figure 2A).

Notably, no difference was found between the three diagnostic groups and the control group in identifying the stories that did not contain the Faux Pax motif (Kruskal–Wallis test, χ²₍₃₎ = 4.48, p = 0.21, N = 84; Figure 2C). However, in comparison with the healthy individuals, all the three diagnosis groups received a lower score on the comprehension questions (Kruskal–Wallis test, χ²₍₃₎ = 31.19, p < 0.001, N = 84; adjusted using the Bonferroni correction, p < 0.001; Figure 2D). However, there was no significant difference between the three diagnosis groups (Bonferroni correction, p > 0.05; Figure 2D).

The Z-score analysis revealed a significant difference between groups in the Faux Pas motif stories (FP) [males: F_(3,48) = 15.18, p < 0.001; females: _(3,28) = 20.99, p < 0.001, Figure 2D,G], and in the Non-Faux Pas motif stories (NFP) [males: F_(3,48) = 100.57, p < 0.001; females: _(3,28) = 31.39, p < 0.001, Figure 2E,H]. Post hoc analysis shows that all three diagnosis groups have a lower Z-score of FP and NFP among males and females than the control group (Figure 2D,E,G,H). Interestingly, among females, the BPD group was found to have a higher Z-score of FP than the schizophrenia group and a higher Z-score of NFP compared to the schizophrenia and schizoaffective groups (Figure 2D,E). In addition, the total ToM ability Z-score was significantly different between groups [males: F_(3,48) = 56.40, p < 0.001; females: _(3,28) = 69.38, p < 0.001, Figure 2F,I]. Post hoc analysis shows that all three diagnosis groups have a lower ToM Z-score among males and females than the control group (Figure 2F,I). However, among females, the BPD group had a higher ToM Z-score than the schizophrenia and schizoaffective groups (Figure 2F).

3.4. Assessment of Autistic Symptoms and Empathy

The degree of autistic symptoms and the level of empathy were assessed using the AQ and EQ questionnaires, respectively. Two-way ANOVA analysis revealed no significant main effect of sex effect in the Autism Spectrum Quotient (AQ) [F_(3,76) = 0.316, p = 0.57, η² = 0.004]. Therefore, both sex groups were analyzed together. The analysis revealed a significant difference in AQ score between the groups [F_(3,80) = 5.06, p = 0.003, Figure 3A]. Thus, individuals with schizophrenia and persons with BPD received a higher score of AQ compared to the control group (Figure 3A). However, no difference in the AQ scores was observed between individuals with schizoaffective disorder and the control group (Figure 3A), and between the three diagnosis groups (Figure 3A).

In contrast, analysis of the level of empathy showed a significant main effect of diagnosis and sex [F_(3,76) = 17.44, p < 0.001, η² = 0.408; F_(1,76) = 8.21, p = 0.005, η² = 0.098, respectively], with no significant interaction between the factors [F_(3,76) = 1.49, p = 0.22, η² = 0.056]. Overall, the EQ scores were found to be lower in all the diagnostic groups as compared with the control group (Tukey’s, p < 0.005, Figure 3B). In addition, the EQ score of the BPD group was significantly higher compared to the schizophrenia group, but not the schizoaffective group (Figure 3B). Notable, no difference in the EQ scores was observed between individuals with schizoaffective disorder and schizophrenia (Figure 3B). Regarding the effect of sex on EQ scores, overall, the EQ scores were higher in the female group as compared with the male group (t₍₈₂₎ = −4.08, p < 0.001). Interestingly, female PBD patients scored more than male PBD patients in the EQ (t₍₉₎ = −3.01, p = 0.01). No difference in the EQ scores was found between male and female schizophrenic, schizoaffective, and control individuals (t₍₄₂₎ = −0.355, p = 0.72; t₍₉₎ = −0.817, p = 0.43; t₍₁₆₎ = −1.41, p = 0.21, respectively).

3.5. Correlation Analysis Between the Eyes Test, Faux Pas, EQ, and AQ

Pearson’s correlation analyses showed that EQ scores were significantly correlated with the eyes test (r = 0.599, p < 0.001, Figure 3C) and Faux Pas motif recognition (r = 0.711, p < 0.001, Figure 3D). Furthermore, a significant correlation was found between the eyes test and Faux Pas motif recognition (r = 0.697, p < 0.001, Figure 3E), and no correlation was found between scores of AQ and the eyes test or Faux Pas motif recognition (r = −0.176, p = 0.10; r = −0.141, p = 0.20, respectively).

4. Discussion

Impairment of social abilities, interpersonal relationships, and social cognitive functioning characterize severe mental health and developmental disorders such as schizophrenia, depression, personality disorders, and autism. Studies have reported impairment in mentalizing and understand that others have their thoughts, beliefs, emotions, and intentions among those diagnosed with schizophrenia, depression, and borderline personality disorder [12,22]. To the best of our knowledge, there is no comprehensive research comparing the mentalization level between different mental health diagnoses.

In the current study, we explored the mentalization capability of three groups of patients with other psychiatric diagnoses (schizophrenia, schizoaffective disorder, and borderline personality disorder). We evaluated their autistic symptoms and their level of empathy. Our results suggest that the cognitive and affective aspects of ToM are impaired among all of the diagnostic groups. Additionally, we found a correlation between the degrees of empathy, but not autistic characteristics, and the level of performance in the mentalization tests, suggesting that the ability to infer the emotional experience of others might predict the status of the performance in ToM tasks. The primary outcome of the current study is the ability to identify the emotional state of others and recognize that social motifs are impaired among all three diagnostic groups.

Studies comparing the ToM ability of individuals with schizophrenia with schizoaffective patients are contradictory, and include inconsistent results. Here, we demonstrated that the performance level of schizoaffective patients in both ToM tasks (decoding the emotion of others and understanding an abnormal social situation) was similar, indistinguishable from individuals diagnosed with schizophrenia, and significantly lower than the healthy individuals. These results align with previous studies [10,23]. Nevertheless, other works reported that the level of performance of ToM tasks was to the same extent [24,25,26].

Additionally, the performance level in the ToM task was similar between the three-diagnostic groups (borderline personality disorder, schizophrenia, and schizoaffective disorder). It should be noted that the performance of BPD in the eyes test was also indistinguishable from the schizophrenic and schizoaffective individuals, but was different from the control group. The last result goes hand in hand with the published literature, which separately investigated BPD persons [12,27,28]. A different pattern of social cognitive abilities was reported between women with schizophrenia and women with BPD. Although schizophrenic women performed below women with BPD in a social cognition task, the magnitude of the errors was higher in the BPD than in the schizophrenic group [29]. In another study, a different pattern of social cognition impairment between BPD and schizophrenia was reported. Schizophrenic individuals’ error types were under-mentalizing, and those of BPD were over-mentalizing; thus, they are more likely to make overly complex mental state inferences. Both individuals with schizophrenia and those with BPD underperformed as compared to the control group [30]. In the current study, we did not observe any differences in the mental state decoding error pattern and reasoning between schizophrenic, schizoaffective, and BPD individuals. However, individuals with schizophrenia made more errors in the recognition task and the comprehension questions than the other diagnostic groups, suggesting a more severe cognitive impairment of the schizophrenic subjects. More importantly, we found that women with BPD perform significantly better in the recognition task than women with SZ and SZaff. To the best of our knowledge, this is the first report indicating such a difference in ToM task performance among women with BPD, SZ, and SZA. In contrast, analysis of the men’s performance revealed no difference between the three diagnostic groups. Taken together, ToM performance is not associated with any of the three diagnostic groups per se, and highlights the need for more sensitive ToM tasks for future clinical diagnosis tools.

A correlation was found between the ability to mentalize and empathy. Here, we report a positive correlation between the ability to identify the other’s emotions on the eyes test and the score of the empathy questionnaire. A person who understands and decodes the mental state of others will probably have higher empathy. This result is consistent with past studies, which showed a correlation between the effective aspect of ToM and empathy [31,32]. In addition, we also reported on a correlation between the EQ scores and the recognition of social motifs. This result is not surprising, since it has been found that people with high empathy more successfully interpret and understand complex social events. For example, a correlation between empathy and performance in false belief ToM tests was found [33] It is important to note that, regardless of diagnosis, the control group and individuals with mental illness scored above average and average on the EQ questionnaire, respectively [20]. These data suggest that, on average, all of the diagnosis group participants can understand how other people feel and respond appropriately. In contrast to the correlation between ToM and empathy, no association was found between the cognitive and affective aspects of ToM and the AQ score. In addition, it is essential to emphasize that the scores of all of the research groups in the AQ questionnaire are in the normal range, and do not indicate autistic-like traits or phenotypes [21]. Together, the results suggest that the impairment in the level of performance on both emotional and Faux Pas motif recognition tests probably did not result from autistic-related traits, as measured by the AQ questionnaire, that characterize schizophrenia and other psychiatric disorders.

To correctly interpret the study findings, it is essential to address its limitations. This initial study included a small number of schizoaffective and BPD patients, and did not include recruitment from the outpatient clinics and the community. Additionally, here the size of each group was modest, which may influence the interpretation of the findings. Therefore, replications among larger samples are critical in order to establish the validity of current findings and infer on their practical implications. Although statistically significant differences were found, this study should be repeated in a larger group of subjects, including, among others, people who are not hospitalized patients. Second, we included individuals with comorbid affective disorders in the BPD group. Thus, we could not rule out that part of the affective and cognitive impairment of ToM is simply due to the influences of this comorbidity. Finally, the duration of the schizophrenic and schizoaffective patients was longer than the BPD group, suggesting a chronic course of the illness, probably with cognitive decline over the years that could explain why schizophrenic patients score lower in the comprehension questions.

Despite the current limitations, here, we provide evidence that the cognitive and affective aspects of ToM are impaired in individuals with schizophrenia, schizoaffective disorder, and BPD, and that the level of the impairment did not differ between the diagnostic groups among men. However, in women with BPD, the cognitive and affective aspects of ToM are less impaired compared to individuals with schizophrenia and schizoaffective disorder. Moreover, our data suggest that this impairment is associated with decreased empathy. Our findings challenge the ability to use ToM as a differential diagnostic tool, especially among men, raising questions about the link between social skills and ToM performance.