Theory of Mind in patients at clinical high risk for psychosis.

BACKGROUND

Patients with schizophrenia have a decreased ability to interpret the intentions of other individuals, called Theory of Mind (ToM). As capacity for ToM normally advances with brain maturation, research on ToM in individuals at heightened clinical risk for psychosis may reveal developmental differences independent of disease based differences.

METHODS

We examined ToM in at clinical high risk and schizophrenia patients as well as healthy controls: 1) 63 clinical high risk (CHR) patients and 24 normal youths ascertained by a CHR program; and 2) in 13 schizophrenia cases and 14 normal adults recruited through a schizophrenia program. ToM measures included first- and second-order false belief cartoon tasks (FBT) and two "higher order" tasks ("Strange Stories Task" (SST) and the "Reading the Mind in the Eyes" task). In the first study, CHR patients and normal youths were also assessed for cognition, "prodromal" symptoms and social function.

RESULTS

Errors on first- and second-order false belief tasks were made primarily by patients. CHR patients and their young comparison group had equivalent performance on higher order ToM, which was not significantly different from the worse ToM performance of schizophrenia patients and the higher performance of normal adult controls. In the combined dataset from both studies, all levels of ToM were associated with IQ, controlling for age and sex. ToM bore no relation to explicit memory, prodromal symptoms, social function, or later transition to psychosis.

CONCLUSIONS

Higher order ToM capacity was equally undeveloped in high risk cases and younger controls, suggesting that performance on these tasks is not fully achieved until adulthood. This study also replicates the association of IQ with ToM performance described in previous studies of schizophrenia.