Elementary cognitive subprocesses in a double-blind study of haloperidol and risperidone in subchronic schizophrenic patients

Recent studies have shown advantages of the atypical neuroleptic agent risperidone against conventional neuroleptic agents in order to enhance or maintain cognitive abilities. It is not yet clear whether unspecific or selective pharmacological manipulation of cognitive subprocesses is responsible for differences in psychometric tests. To answer this question we used the reaction-time decomposition task by Donders (1868) in a double-blind trial of haloperidol and risperidone.

23 subchronic patients with the diagnosis of a schizophrenic disorder (DSM-IV) were randomly assigned under double-blind conditions to each group (4–16mg/d haloperidol or 2–8mg/d risperidon) for a treatment of 168 days. At day 0, 35 and 168 patients had to do single-, discriminant- and choice-reaction tasks. Clinical symptoms were assessed with PANSS and SANS, extrapyramidal side effects with ESRS.

There were no differences in clinical efficacy between substances. More patients of the risperidone group reached the end of the trial (chi²=6.7, p<.01). Patients treated with risperidone had shorter reaction times in all tasks. The highest shortening was found in choice-reaction tasks (p<.01). Patients under the initial treatment (35 days) of haloperidol with improvement in response-selection processes and those with slower reaction-times in the risperidon group tended to cancel the treatment.

Results underlie the central role of disturbance of response-selection in treatment of schizophrenic disorder. It seems to be important for long-time treatment with conventional and atypical substances, whether and in which degree neuroleptic treatment affects these processes.