Higher order theory of mind in patients with bipolar disorder and schizophrenia/schizoaffective disorder

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 = 47, SCH = 47). 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 < 0.001, η_p^2 = 0.144). Regression analysis in the total sample showed that a diagnosis of SCH and lower IQ were associated with lower HT scores ( R 2 = 0.316, p < 0.001). In the BD group, verbal memory and processing speed were the main predictors of HT performance ( R 2 = 0.344, p < 0.001). 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.