Executive functioning in schizophrenia: a thorough examination of performance on the Hayling Sentence Completion Test compared to psychiatric and non-psychiatric controls.

BACKGROUND

The current study examined executive functioning in schizophrenia by assessing response initiation and suppression in a group of schizophrenia patients, and drawing comparisons with psychiatric and non-psychiatric control groups.

METHOD

The Hayling Sentence Completion Test was used as a measure of executive functioning and was completed by 39 schizophrenia patients, 40 bipolar disorder patients and 44 healthy control participants. Outcome measures included response initiation and response suppression latency and error rate.

RESULTS

The schizophrenia group was significantly impaired on all measures of the Hayling Sentence Completion Test when compared to healthy control participants, and only on some of the measures when compared to the bipolar disorder group. The bipolar disorder group did not differ in performance compared to the healthy control group. Overall schizophrenia patients showed longer response initiation and response suppression latencies, and an increased error rate. Performance of the schizophrenia patients was associated with higher ratings of cognitive disorganisation. Performance was not related to age, gender, predicted IQ or any other clinical characteristics.

CONCLUSIONS

Schizophrenia patients show a slowing in baseline response initiation and slowed suppression of an inappropriate response. Considering the bipolar disorder patients demonstrated intact performance, altered executive functioning in schizophrenia appears relatively specific to the disorder rather than reflecting other characteristics common to mental illness. Investigations examining which neurocognitive domains are impaired in schizophrenia provide direct implications for treatment options tailored to an individual's cognitive strengths and weaknesses.