Background. A cardinal feature of schizophrenia is the
sufferer's difficulty in interacting
appropriately within the social milieu. This deficit has recently
been associated with the concept of
theory of mind, more commonly construed as a working model to understand
in autistic children. In this paper the complex relationships between theory
of mind, IQ and
psychoses are addressed.
Methods. Five experimental groups were used; non-psychiatric
controls, affective disorder,
schizophrenia with normal pre-morbid IQ, schizophrenia with pre-morbid
IQ in the mildly learning
disabled range, and mild learning disability with no history of
psychiatric illness. All subjects were
given a first order Theory of Mind Task and if successful, a second order
Theory of Mind Task was then administered. All subjects were rated using
Positive and Negative Symptom Scale (PANSS).
Results. Subjects with schizophrenia and subjects with mild
learning disability show impaired
ability on a second order theory of mind task. However, when patients who
are unable to answer
reality questions are removed from the analysis specific impairment of
theory of mind is only seen
in subjects with schizophrenia. Furthermore, this impairment is
relatively specific to particular
psychopathological clusters in subjects with schizophrenia. Even though
the same clusters of
psychopathology are also seen in patients with affective disorder, their
presence is not associated with poor second order theory of mind performance.
Conclusions. Impaired theory of mind on second order tests
specific to schizophrenia when
compared to mild learning disability and affective disorder control groups.
schizophrenia and pre-morbid mild learning disability show greater
impairment than subjects with
schizophrenia and a pre-morbid IQ within the normal range.