The role of cognition in the risk--benefit and safety analysis of antipsychotic medication.

Conventional neuroleptics can further reduce cognitive function, which is already impaired in most patients with schizophrenia. Although some areas of cognition may remain relatively well preserved in schizophrenia, it has been suggested that the origins of a neurocognitive decline in schizophrenia may be related to a reduction in dopamine activity in the prefrontal cortex. If this is the case, dopamine D2 blockade would be expected to impair some aspects of neurocognitive function further. The level of neurocognitive function in schizophrenia is related to vocational and social ability, and the course of cognitive decline appears to be consistent with a static encephalopathy, rather than progressive dementia. Intensive cognitive retraining in patients with schizophrenia may improve, but not normalize, some aspects of cognitive performance. Most cognitive deficits remain stable, even when improvements in symptoms are obtained with antipsychotic treatment. Drugs such as risperidone, one of the newer serotonin-dopamine antagonists (SDAs), have a better effect on cognitive function than conventional antidopaminergic neuroleptics, and are therefore more likely to enable the patient to benefit from cognitive and other forms of training. Anticholinergic drugs used to treat EPS, or drugs with anticholinergic activity, also impair cognitive function. Consequently, because the need to use anticholinergic drugs is less with the SDA antipsychotics, the cognitive function of patients treated with drugs such as risperidone is likely to be better than it would be if they took a conventional neuroleptic.