Theory of mind and schizotypy: A meta-analysis

Schizotypy is a multi-dimensional personality construct that putatively indicates an individual's liability to psychosis. Schizophrenia is associated with significant deficits in theory of mind (ToM). However, previous studies investigating the relationship between schizotypy and ToM provided inconsistent findings. Following the systematic review of all relevant schizotypy studies between January 1, 1980 and June 30, 2019, a meta-analysis of the relationship between ToM and schizotypy was conducted. Current meta-analysis included 24 studies consisting of 4162 healthy individuals. Overall, there was a significant but a small negative relationship between ToM and schizotypy (d = -0.23, CI = -0.14-0.33). Schizotypy scores were negatively associated with both reasoning (d = -0.24, CI = -0.11-0.38) and decoding (d = -0.21, CI = -0.09-0.32) aspects of ToM. The relationship between ToM and schizotypy was more significant in the studies using extreme-group design (d = -0.31, CI = -0.17-0.45) than non-extreme-group design (d = -0.17, CI = -0.04-0.29). ToM abnormalities were significantly related to both positive and negative schizotypy. Current findings support the continuum between schizotpy and schizophrenia. ToM abnormalities might be vulnerability markers for psychosis.