Abstract

     Some evidence suggests that patients with bipolar disorder (BD) have better Theory of Mind (ToM) skills than patients with schizophrenia/schizoaffective disorder (SCH). However, this difference is not consistently reported across studies, so rather than being global, it may be restricted to specific aspects of ToM. Our primary objective was to compare higher order ToM performance between BD and SCH patients using the Hinting Task (HT). Ninety-four remitted patients were recruited (BD = ۴۷, SCH = ۴۷). Intelligence quotient (IQ), attention, memory, executive functions, and processing speed were also assessed. Patients with BD performed better on the HT than patients with SCH, even when the analysis was adjusted for IQ and neurocognition (p < ۰٫۰۰۱, η۲p = ۰٫۱۴۴). Regression analysis in the total sample showed that a diagnosis of SCH and lower IQ were associated with lower HT scores (R2 = ۰٫۳۱۶, p < ۰٫۰۰۱). In the BD group, verbal memory and processing speed were the main predictors of HT performance (R2 = ۰٫۳۴۴, p < ۰٫۰۰۱). In the SCH group, no variable was significant in explaining HT performance. In the context of previous studies that found no significant differences in the most basic aspects of ToM (e.g., understand other people’s thoughts/beliefs), our results suggest that differences between the two disorders might be limited to the more challenging aspects (e.g., understand the intended meaning of indirect requests). No causal inferences can be made in this cross-sectional study. However, regression analyses show that whereas in BD patients, ToM functioning would be partially modulated by neurocognitive performance, in SCH patients, it could be largely independent of the well-known neurocognitive impairment.

Introduction

     “Theory of Mind” (ToM) encompasses the ability to understand the cognitive and afective mental states of oneself and others and the ability to use this knowledge to predict and anticipate people’s behavior [1]. Patients with bipolar disorder (BD) and schizophrenia/schizoaffective disorder (SCH) show mild-to-severe defcits in ToM throughout the course of the disease, including the prodromal, acute, and remitted phases [2, 3]. Although less severe, similar difculties have been observed in their unafected frst-degree relatives, suggesting some degree of heritability and that ToM difculties are a vulnerability marker for BD and SCH [4, 5].

     ToM is more closely related to social functioning than most clinical and neurocognitive variables. Therefore, an intact ToM is essential for adequate performance at work and in the community [6, 7]. However, it is not a monolithic function. Instead, it consists of several sub-processes among which the frst-order ToM (i.e., the ability to know what another person thinks or believes), the second-order ToM (i.e., the ability to know what a person thinks that another person thinks or believes) and other forms of higher order ToM (e.g., understand sarcasm, metaphors or indirect requests) stand out [8].

Conclusion

     Our results show that patients with BD perform signifcantly better on higher order ToM than patients with SCH, independent of group diferences in other neurocognitive domains, but that general intelligence infuences this difference. Contextualized in the current literature, the present fndings suggest that the diferences between the two disorders may be subtler than previously thought, mainly afecting the more complex and sophisticated aspects of ToM. As clinical implications, both groups of patients could beneft from rehabilitation interventions designed to improve cognitive functioning. However, whereas BD patients would beneft from rehabilitation of verbal memory and processing speed [61], in SCH patients, additional efort should be made to rehabilitate the more challenging aspects of ToM [62]. Our fndings also have practical implications for how we should communicate with patients with BD and, especially, SCH. Ambiguity, irony, and the use of double meanings are frequent sources of misunderstanding and should be avoided.