Social functioning impairment can be a clue to understand interpersonal problems associated with two of the most common mental illnesses namely, schizophrenia and BPD [23]. The interpersonal changes associated particularly with BPD involve affective, cognitive, behavioral, and disturbed relatedness symptoms, whereas negative symptoms of asociality, avolition, social withdrawal, and poor social skills are the characteristics of schizophrenia [4]. Interestingly, there is a strong evidence that ToM is considered a core concept in social functioning which can be used as a diagnostic criterion in these mental illnesses.
To our knowledge, there are inconsistent results regarding theory of mind (mentalization) processes, and what type of mentalization errors, occurs in patients with schizophrenia or BPD. Also, there is a lack of studies that linked ToM to suicidality in both BPD and schizophrenia.
This study aimed to assess affective ToM in BPD patients compared to schizophrenia patients and healthy controls and to identify the impact of ToM functioning and its clinical correlates to suicidal probability in the three groups.
Affective ToM was assessed by RMET as the most common measure for understanding how people process other’s feelings and emotions [24, 25], and it was obvious that BPD had superiority in RMET score than control or schizophrenic patients (P<.001), which means that BPD patients have enhanced affective theory of mind (hypermentalization). This has an agreement with findings of two similar studies [26, 27]. Another study has agreed with ours where BPD patients with and without the major depressive disorder (MDD) were found scoring higher in affective ToM using RMET, particularly those without MDD [28]. This also supports earlier study findings that individuals with BPD are more accurate than healthy controls at detecting certain emotional states in facial emotion recognition tasks [29, 30].
Also, Normann-Eide and colleagues have agreed with our study results in that BPD patients were found to have a tendency to hypermentalize where ToM was investigated by the Movie for the Assessment of Social Cognition. Also, the study concluded that there was an association between hypermentalization and interpersonal problems in BPD patients and that they tend to misinterpret social information [31].
In line with our results, a study by Ortega-Díaz and colleagues has revealed that BPD patients have ToM deficits in the form of overmentalization when investigated by MASC and social functioning scale. Also, their first-degree relatives showed significant differences in social functioning with regard to family relationships and interpersonal behavior compared to controls [14]. Consequently, according to all the mentioned studies BPD patients have increased sensitivity to the mental states and social signals of others which may be an explanation for the social function difficulties.
Nevertheless, our results contradict other studies like a study by Levine et al. (1997) which found that individuals with BPD were less accurate at facial recognition tasks than healthy controls [32], a finding also supported in a later study by Bland and colleagues [13]. In addition, a study by Górska and Marszał revealed no difference in BPD patients and the control group in ToM level and the study relates such controversy of their results to a small sample size as well as the large intragroup differences particularly in education and age [8]. Similarly, the findings of an earlier study conducted by Preißler et al. did not report differences in mentalizing between BPD and healthy subjects [33]. However, in this study, some patients were medicated with psychotropic medications, which may have influenced the results.
Came in the same line, another study by Petersen and colleagues that have revealed the equal capability of both BPD and control groups in undertaking simple mentalization tasks, yet deficits in mentalization were detected in more complex tasks. The study showed significantly more mentalization errors on affective and cognitive understanding of faux pas and a Joke Appreciation task [34].
In schizophrenia, our study results have revealed a lower RMET score compared to both BPD patients and healthy controls indicating a deficit in ToM (hypomentalization) (P<0.001). This goes with the results of García-Fernández and colleagues which compared the performance of 90 patients with schizophrenia in both first episode and chronic stage versus healthy controls using two ToM tasks (Hinting Task and RMET) and schizophrenia patients showed significantly poor performance than controls with more worsening in chronicity [35]. Another agreement came from a meta-analysis was conducted to answer a question regarding the possible impairment in ToM in schizophrenia and revealed a significant mentalization impairment in schizophrenia. Interestingly, patients in remission were also impaired which supports that mentalizing deficit is a core feature in schizophrenia, which agrees with the findings of our study [36].
Furthermore, by using another scale to assess ToM functioning as in a study done by Abdel-Hamid and her colleagues (2009) who used a computerized theory of mind (ToM) test consisting of a picture sequencing task and a questionnaire, ToM deficits existed in schizophrenia patients more frequently than controls [37]. Going through all of this research, we emphasize the fact that impairment in ToM is a stable trait feature in patients with schizophrenia.
In contrast, older studies that used another tool for ToM assessment compared patients with different symptom profiles or remitted to controls. Generally, it was concluded that deficits are only related to the severity of symptoms [38,39,40].
Suicide is a major psychiatric emergency, as the second leading cause of death in youth among adolescents and young adults [41].
In our study, BPD patients had superiority in suicide probability score than both patients with schizophrenia and healthy controls. Moreover, findings from the current study reveal that hypermentalization (enhanced affective ToM) detected in BPD patients shares a significant relation with suicidal probability. However, hypomentalization (less ToM) detected in schizophrenia had a non-significant relation with suicidal probability. This is in agreement with the findings of a study by Hatkevich and colleagues which revealed a significant relation between hypermentalization and suicide in adolescence [25].
In addition, several studies have suggested that individuals who engage in self-harm behaviors have significant hypermentalization errors that lead to difficulties with managing specific mental states and emotional dysregulation [42, 43]. Similarly, other findings proposed that these behaviors are coping strategies to alleviate negative effect resulting from hypermentalizing state [44].
To explain, Allen et al. (2008) named patients who have enhanced mental sensitivity to social signals by pseudo-mentalizing style, as they are overconcerned with the interpretation of information from others’ mental states or emotions [45], which may be under affection by their own memories and personal beliefs [46]. Therefore, hypermentalizing is maladaptive for interpersonal functioning, as it may lead individuals to assume malevolent intentions of others and inappropriately respond (e.g., poor peer relations, misunderstanding of social interactions, severe rejection sensitivity, and loss of social support), all of which could underlie and exacerbate the emotion dysregulation [47,48,49].
So, Hatkevich et al.’s study has pointed out the importance of (1) early detection of patients with pseudo-hypermentalization tendency and (2) providing secondary prevention programs to adjust mentalizing style [25].
In contrast, Laghi et al.’s (2016) found mentalization skill deficits in patients with self-harm behaviors, compared to the controls. The differences between the studies’ results could have been attributed to different tools used. Laghi et al. used the Theory of Mind Assessment Scale (TH.o.m.a.s), a semi-structured interview that assesses the subject’s understanding of other’s mental states in different situations [50].
Impairments in overall ToM especially the affective part are associated with suicidal probability. Therefore, psychotherapy programs which target mentalization skills hold promise for suicide risk identification, treatment, and prevention work.
Thus, current findings support results of previous treatment-based research, suggesting that interventions targeting social-cognitive processes and defects in mentalization as mentalization-based therapy (MBT) may be helpful in improving ToM impairments and associated suicide in BPD. For example, 3 previous RCT assessed the effects of MBT in BPD compared to standard clinical management. It was found that MBT was superior in terms of its effects on suicide attempts and self-harm. The experienced reduction in suicidality was sustained at the 5-year follow-up [51,52,53].
In schizophrenia, a significant high suicide probability existed compared to control (P< <0.001). However, unfortunately, the correlation between RMET and suicidality assessed by SPS could not be proven with a significant difference in this study except for the hopelessness subdomain (R= −0.526, P= 0.017), though insignificant weak inverse relation existed between all suicide probability score domains and RMET. This is inconsistent with findings of the study by Canal-Rivero and colleagues conducted in 2019 to investigate the factors associated with multiple suicidal attempts in patients with the first episode of psychosis, and they found that patients with ToM deficit detected by false belief task (FBT) made more suicidal attempts than those without (P=0.02). Moreover, errors in FBT were predictors of the number of suicides attempts in those patients (B=0.48, t=2.11, P=0.04) [54]. Similarly, in an earlier study, ToM impairment was associated with suicidal behaviors in schizophrenia [55]. This finding also supported by a recent study revealed that social cognitive impairment is a predictor of suicidal behaviors in schizophrenic patients [56]. This controversy could owe to different tests used to investigate mentalization skills, different study designs, and criteria of the included participants.
Our study is limited by the small sample size, our sample is comprised of females only due to few numbers of males presented with BPD at our institute. So, our results cannot be generalized to whole BPD and schizophrenia patients. A second limitation is that not all domains of social cognition were assessed only affective ToM, as well we did not examine more complex mentalizing tasks to give more illustration of the magnitude and different patterns of social cognitive problems in BPD and schizophrenia. Therefore, further investigations are urged for further validation of the current evidence.