MedWire News: Theory of mind (ToM) impairment in schizophrenia spectrum disorders and bipolar disorder appear to reflect underlying general cognitive deficits and residual symptoms, rather than being a specific trait-marker, the results of an Australian study indicate.

There is a degree of debate as to whether ToM impairments represent a trait-marker for schizophrenia or are related to the expression of delusions or disorganization, and there is evidence to suggest that ToM impairments may be a trait marker for all psychoses. However, the findings have so far been inconclusive.

To investigate further, Emre Bora (University of Melbourne) and colleagues searched the PubMed and PsychINFO databases for empirical studies examining ToM impairments in remitted schizophrenia patients, first-episode psychosis patients, individuals at high risk of psychosis, and first-degree relatives of schizophrenia patients.

In addition, the team searched for studies of ToM impairments in patients with schizophrenia spectrum disorders, affective psychosis, and bipolar disorder, yielding a total of 108 studies selected for further investigation.

The results, published in the journal Acta Psychiatrica Scandinavica, demonstrate that despite differences between studies in the criteria used to define the groups of individuals investigated, ToM abnormalities were found during first-episode psychosis, persist into schizophrenia, and are retained even when patients are in remission.

To a lesser extent, high-risk individuals and unaffected first-degree relatives also had ToM impairments, as did schizophrenia spectrum disorder, affective psychosis, and bipolar disorder patients. However, it was noted that cognitive deficits and subclinical symptoms could not be ruled out as contributing to the findings.

The researchers conclude: “While available studies have provided important insights into the nature of ToM impairment in major psychoses, there remain many unanswered questions in this area.

“Further studies are needed to investigate ToM impairments in patients with affective disorders and in their first-degree relatives. The effects of demographic variables, state variables and cognitive deficits on observed ToM deficits should be more carefully investigated.”

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