Functional Impairments and Theory of Mind Deficits in Schizophrenia: A Meta-analysis of the Associations

Schizophrenia is associated with major functioning difficulties. Theory of mind (ToM), the ability to infer the mental states of others, is an important determinant of functioning. However, the contribution of ToM to each specific domain of functioning remains to be better understood. The objectives of this meta-analysis were to document and compare the magnitude of the associations between ToM and (1) different domains of functioning (social functioning, productive activities, and instrumental activities of daily living), each assessed separately for functional performance and functional outcome and (2) different aspects of functioning (functional performance and functional outcome) in schizophrenia. Fifty-nine studies (N = 4369) published between 1980 and May 2019 targeting patients with schizophrenia or schizoaffective disorder aged between 18 and 65 years old were included. Studies were retrieved from seven databases. Correlations were extracted from the articles, transformed into effect sizes Zr and combined as weighted and unweighted means. The strength of the associations between the domains and aspects of functioning were compared using focused tests. A moderate association was observed between ToM and all domains of functioning, with a stronger association between ToM and productive activities compared with social functioning (only for functional outcome [χ2(2) = 6.43, P = 0.040]). Regarding the different aspects of functioning, a stronger association was observed between ToM and functional performance, compared with functional outcome, for overall functioning (χ2(1) = 13.77, P < 0.001) and social functioning (χ2(1) = 18.21, P < 0.001). The results highlight a stronger association of ToM with productive activities and with functional performance, which should be considered in future studies to improve functional recovery in schizophrenia.