Recent empirical findings suggest that notable similarities are shared by a wide range of neuropsychiatric disorders in genetic, neuroanatomical, neuropsychological and behavioural aspects. Theory of mind (ToM), the ability to infer the mental state of other people, is an important neurocognitive function frequently impaired in patients with schizophrenia, major depressive disorder, bipolar disorder, and autism spectrum disorders. Although quite substantial studies on ToM have been conducted in each of these diagnostic groups, very few previous studies have directly compared the ToM ability between IQ-matched individuals across these diagnostic groups. Of the limited studies making direct comparison between groups, most of them were limited to two clinical groups comparison and the results were confounded by a unitary ToM assessment. Accumulating studies have suggested that there are dissociable cognitive and affective components of ToM. Cognitive component of ToM refers to the ability to infer someone’s beliefs, whereas affective component of ToM refers to the ability to infer someone’s feelings. There is a gap of knowledge in understanding the affective-cognitive facets of ToM across these diagnostic groups thoroughly.
To bridge this gap of knowledge, Dr. Raymond Chan and his team from the Neuropsychology and Applied Cognitive Neuroscience (NACN) Laboratory, Key Laboratory of Mental Health, the Chinese Academy of Scienceshave conducted two studies specifically examining the ToM performances in these clinical groups. The first study recruited demographically matched 35 participants with schizophrenia (SCZ), 35 with bipolar disorder (BD), 35 with major depressive disorder (MDD), and 35healthy controls. They administered the Yoni task that specifically captured both the cognitive and affective components of ToM at the first- and second-order levels.
Their findings showed that ToM impairments were observed in all patient groups compared with healthy controls. Patients with SCZ performed worse than those with BD. In second-order conditions, patients with SCZ and MDD showed deficits in both cognitive and affective conditions, while patients with BD performed significantly poorer in cognitive conditions. Network analysis results also showed that second-order affective ToM performance was associated with psychotic and depressive symptoms as well as executive dysfunction, while second-order affective ToM performance and negative symptoms showed relatively high centrality in the network.
In the second study, Dr. Chan’s team collaborated with psychiatrists from Castle Peak Hospital to examine the ToM performance in high-functioning autism patients and schizophrenia patients.They recruited 30 high-functioning autism patients, 30 schizophrenia patients, and 30 controls, and utilized the cartoon-based Yoni Task and the verbal-based Faux Pas Task. The results showed that high-functioning autism patients are more severely impaired in verbal-based ToM, but shared similar visual-based ToM impairments with schizophrenia patients. These findings support contribute to the growing evidence for shared mentalising network between the two disorders.
Taken together, these two studies support the notion of shared ToM impairments observed across different neuropsychiatric disorders, and contribute to the growing evidence for shared mentalising network between these disorders. However, on the other hand, the different ToM performance across diagnostic groups and the association between ToM performance and clinical symptoms suggests that the severity and persistence of ToM impairments may offer information in addition to differential diagnosis.
These studies were supported by the National Basic Research Programme of China, the National Science Fund China, the Beijing Training Project for the Leading Talents in Science and Technology, the Beijing Municipal Science & Technology Commission Grant, the CAS Key Laboratory of Mental Health, Institute of Psychology, and the Philip K. H. Wong Foundation.
The papers are now available from Schizophrenia Research and Psychological Medicine.
Wang, Y. Y., Wang, Y.*, Zou, Y. M., Ni, K., Tian, X., Sun, H. W., Lui, S. S. Y., Cheung, E. F. C., Suckling, J., Chan, R. C. K.* (2017). Theory of mind impairment and its clinical correlates in patients with schizophrenia, major depressive disorder and bipolar disorder. Schizophrenia Research, https://doi.org/10.1016/j.schres.2017.11.003
Tin, L. N. W., Lui, S. S. Y.*, Ho, K. K. Y., Hung, K. S. Y., Wang, Y., Yeung, H. K. H., Wong, T. Y., Lam, S. M.,. Chan, R. C. K., Cheung, E. F. C. (2017). High-functioning autism patients share similar but more severe impairments in verbal theory of mind than schizophrenia patients. Psychological Medicine, doi:10.1017/S0033291717002690