Background. This study examined data from a Danish prospective longitudinal project in attempt to address the state/trait controversy regarding theory of mind deficits in schizophrenia. Deficits in perspective-taking – a component of theory of mind – were investigated prospectively among children who developed schizophrenia spectrum disorders as adults in comparison to children who did not develop schizophrenia spectrum disorders.

Method. A total of 265 high risk and control subjects were studied in 1972. At the time of initial assessment, the Role-Taking Task (RTT) was administered. Two hundred and forty-two of these children were evaluated in 1992 during follow-up examinations. Sixteen developed schizophrenia, 10 developed a schizophrenia spectrum disorder, 70 had outcomes of other psychopathology, and 146 did not develop a mental illness.

Results. Children who later developed schizophrenia or a schizophrenia spectrum disorder had lower RTT scores, controlling for verbal IQ and age, compared to those who did not develop any mental illness. Although in the expected direction, RTT scores for those with schizophrenia spectrum disorders were not significantly different from those who developed a non-psychotic disorder.

Conclusions. Deficits in perspective-taking among children who later developed schizophrenia spectrum disorders suggest that a facet of theory of mind is impaired prior to development of schizophrenia. Our findings lend support to the hypothesis that theory of mind deficits in schizophrenia are trait markers of the disorder.