Cognitive impairment as a core fetature of schizophrenia

Cognitive deficits play a crucial role for both the pathogenesis and prognosis of schizophrenic psychoses. The range of deficits is broad and includes problems in all domains of cognition, including attention, executive functions and memory. Substantial evidence implicates dysfunctions in some cognitive domains (in particular, memory, attention and executive functions) as candidate indicators of vulnerability to schizophrenia. Some of these deficits are present at the onset of the illness, or even prior to it, and often persist after the florid manifestations of psychoses have remitted. Whether cognitive impairment in schizophrenia deteriorates, improves or remains stable across time and whether the pattern of cognitive deficits observed in patients with schizophrenia is specific of this illness remain controversial issues. In patients with schizophrenia it has been found that the relationship between cognitive deficits and social disability is stronger than that between symptoms and social disability. Moreover some researchers have claimed that the enduring cognitive deficits are responsible for the failure of social rehabilitation programs in schizophrenic patients. In the light of these findings, cognitive impairment has recently become an important target of treatment strategies in patients with schizophrenia. Typical neuroleptics, although effective in reducing positive symptoms of schizophrenia, do not treat cognitive impairment. Atypical antipsychotics have proven superior to conventional antipsychotics in reducing neurocognitive dysfunctions; however, whether their impact on neurocognition is primary or secondary to other clinical changes, such as release from side effects, remains controversial. In this review, literature concerning cognitive deficits in schizophrenia will be reviewed, with particular reference to their role in vulnerability to schizophrenia, their longitudinal course as well as relationships with social disability and antipsychotic drug treatment.