Correlations between cognitive performances and psychotic or schizotypal dimensions

To test if specific correlations exist between cognitive measures and psychotic dimensions in schizophrenic subjects and if similar correlations, between cognition and schizotypal dimensions, are present in non-psychotic subjects.

We administered the same battery of cognitive tests (Source Monitoring, Verbal Fluency [VF] and Stroop tests) to schizophrenic subjects (N=54), their first-degree relatives (N=37) and controls (N=41). Scores of negative, positive and disorganisation dimensions were derived from the Signs and Symptoms of Psychotic Illness scale in schizophrenic subjects, and from the Schizotypal Personality Questionnaire in relatives and controls.

In schizophrenic subjects, as hypothesised, the negative dimension correlated with performance on VF and disorganisation with performance in the Stroop test. The positive dimension did not correlate with any cognitive measure. With only one exception, the significant correlations observed in non-psychotic subjects did not match correlations seen in schizophrenic subjects. In non-psychotic subjects greater disorganisation was associated with more clustered words in VF suggesting that excessive automatic spreading of activation in semantic networks could underlie this dimension.

As a whole, data lent partial support to our hypothesis of specific cognitive-clinical correlations in schizophrenic subjects but did not support the existence of similar correlations in non-psychotic subjects.